benzofurans and enadoline

Epilepsy and CNS injury identify a heterogenous group of diseases, many of which exhibit refractoriness (e.g., the partial epilepsies) to established drug therapy or, as in the case of brain and spinal cord injuries of variable etiologies, remain a formidable target for successful drug development. As such, the search for safe, effective antiepileptic and neuroprotective drugs continues. Although several CNS targets have been identified for drug development, especially the excitatory amino acid receptors, free-radical systems, gangliosides, and nitric oxide, etc., the opioid system and its diversity of receptors have, until recently, received little attention. This review attempts to focus on one opioid system, namely the kappa receptor class of opioid ligands, specifically addressing the potential anticonvulsant and neuroprotective properties of the arylacetamide series of kappa opioid analgesics as novel pharmacotherapeutic approaches to the treatment of epilepsy, stroke, or trauma related brain or spinal cord injury.

Topics: Analgesics, Opioid; Animals; Anticonvulsants; Benzofurans; Central Nervous System Diseases; Epilepsy; Humans; Pyrroles; Pyrrolidines; Receptors, Opioid, kappa; Thiophenes

Preclinical studies have demonstrated that kappa-opioid agonists can attenuate the neurochemical and behavioral effects of cocaine that are related to its reinforcing efficacy, suggesting that kappa-agonists may serve as pharmacotherapies for cocaine dependence. This 8-week inpatient study examined the ability of enadoline, a selective and high-efficacy kappa-agonist, and butorphanol, a mixed agonist with intermediate efficacy at both mu- and kappa-receptors, to reduce the direct pharmacodynamic effects and self-administration of intravenous cocaine in humans (n = 8). Acute doses of intramuscular enadoline (20, 40, and 80 microg/kg), butorphanol (1.5, 3, and 6 mg/70 kg) and placebo were examined separately as pretreatments during each of three test sessions with cocaine in a constrained random order. A cocaine dose-effect session (0, 20, and 40 mg cocaine i.v., 1 h apart) examined direct pharmacodynamic interactions on subjective and physiological indices; self-administration sessions examined choice behavior for cocaine (40 mg i.v. for six trials) versus money 1) in the presence of a sample cocaine dose with money choices presented in ascending value, and 2) in the absence of a sample dose with money choices presented in descending values. Enadoline (80 microg/70 kg) significantly (p < 0.05) reduced some of the positive subjective effects of cocaine (e.g., ratings of "high"), while butorphanol failed to modify subjective responses. Both agents were safely tolerated in combination with cocaine without adverse physiological responses. Cocaine self-administration was significantly greater across all pretreatment conditions when the sample dose was given and ascending money choices were used. Enadoline and butorphanol failed to modify cocaine self-administration. These data suggest that these kappa-agonists may be safely administered in the presence of cocaine but do not produce significant attenuation of cocaine's direct effects or self-administration under these acute dosing conditions.

Topics: Adult; Analgesics, Opioid; Benzofurans; Butorphanol; Cocaine; Cocaine-Related Disorders; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Double-Blind Method; Humans; Injections, Intramuscular; Male; Neuroprotective Agents; Pyrrolidines; Receptors, Opioid, kappa; Reinforcement, Psychology

The availability of the highly selective and specific kappa opioid agonist enadoline provides an opportunity to explore the function of kappa receptors in humans and their potential utility as a target for substance abuse pharmacotherapy development.. The purpose of this study was to characterize the pharmacodynamic effects of enadoline, a selective kappa agonist, and to compare it with butorphanol, a mixed mu/kappa agonist, and hydromorphone, a mu agonist, in humans.. Pilot evaluation (n=3) served to establish intramuscular doses of enadoline (20, 40, 80, and 160 microg/70 kg), butorphanol (1.5, 3, 6, and 12 mg/70 kg), and hydromorphone (1.5, 3, and 6 mg/70 kg) of comparable activity. These acute doses were examined under double-blind, placebo-controlled and constrained randomized conditions with a minimum of 72 h between tests in volunteers with polysubstance abuse histories (n=6). Physiological and subject- and observer-rated measures were collected 30 min before and for 4 h after administration.. Enadoline significantly increased measures of sedation, confusion and dizziness, produced visual distortions and feelings of depersonalization, and increased urinary output. The highest dose (160 microg/70 kg) was not tolerated and led to psychotomimetic effects. Hydromorphone produced prototypic mu opioid effects including respiratory depression, miosis, and euphoria. Butorphanol was most similar to hydromorphone and shared few effects with enadoline.. These results are discussed with respect to the potential use and safety of kappa agonists for clinical indications.

Topics: Adult; Analgesics, Opioid; Analysis of Variance; Benzofurans; Butorphanol; Cross-Over Studies; Dose-Response Relationship, Drug; Double-Blind Method; Female; Heroin Dependence; Humans; Hydromorphone; Male; Middle Aged; Neuroprotective Agents; Pilot Projects; Pyrrolidines; Receptors, Opioid, kappa

To study the analgesic efficacy of enadoline, a selective agonist of the kappa-opioid receptor, a double-blind, randomized comparison was made of enadoline versus placebo and a combination of acetaminophen-codeine in patients with pain after surgical extraction of impacted molar teeth. An initial study involving a comparison of enadoline, a combination, and placebo failed to show any analgesic effect of enadoline. Therefore, a second study with the same design but using higher doses of enadoline was conducted. Despite continued safety and tolerability even at the higher doses, enadoline could not be shown to be superior to placebo. The acetaminophen-codeine combination was significantly more effective than enadoline or placebo. Enadoline did not show analgesic efficacy in this study. Possible reasons for this lack of efficacy are discussed.

Topics: Acetaminophen; Adult; Analgesics, Non-Narcotic; Analgesics, Opioid; Benzofurans; Codeine; Double-Blind Method; Drug Combinations; Humans; Male; Molar, Third; Pain, Postoperative; Pyrrolidines; Receptors, Opioid, kappa; Tooth Extraction

Enadoline, a selective agonist of the kappa-opioid receptor, was studied for its analgesic efficacy in patients with pain after obstetric or gynecologic surgery. An initial study involving a comparison of enadoline (2, 5, 15 micrograms), an acetaminophen-codeine (ACET/COD) combination, and placebo showed all treatments to be ineffective analgesics. Therefore, a second study with the same design but using higher doses of enadoline (15 and 25 micrograms) and replacing ACET/COD with morphine 10 mg i.m. was conducted. Enadoline 25 micrograms produced similar pain relief to that of morphine, although of shorter duration, and better than enadoline 15 micrograms or placebo. However, enadoline was associated with dose-limiting neuropsychiatric adverse events, which led to early termination of the study.

Topics: Abdomen; Acetaminophen; Adult; Analgesia; Analgesia, Obstetrical; Analgesics, Opioid; Benzofurans; Codeine; Dose-Response Relationship, Drug; Double-Blind Method; Female; Humans; Middle Aged; Morphine; Pain, Postoperative; Pelvis; Placebos; Pyrrolidines; Receptors, Opioid, kappa

The diuretic effects, pharmacokinetics, and safety of CI-977, a new centrally acting selective kappa-opioid agonist, were determined in 16 healthy subjects. Subjects received single intramuscular doses of CI-977 (5, 15, or 25 micrograms) or placebo 1 week apart according to a randomized, double-blind, placebo-controlled, four-period, crossover design. Serial blood and urine specimens were collected after each dose. Significant dose-related decreases in negative free water clearance and urine osmolality and increases in urine volume were observed after administration of 15- and 25-micrograms doses of CI-977. CI-977 had no effect on urine electrolyte excretion or serum antidiuretic hormone. Absorption of CI-977 was rapid with individual tmax values ranging from 0.17 to 1.5 hours. Cmax and AUC(0-infinity) increased proportionally with dose. Individual elimination half-life values ranged from 0.6 to 3.3 hours and were independent of dose. Changes in free water clearance were related to CI-977 Cmax (r2 = 0.29, P = 0.0001) and AUC(0-4 hr) (r2 = 0.32, P = 0.0001) values. The most frequently reported adverse events after CI-977 administration were dizziness, fatigue, paresthesia, headache, vasodilatation (facial flushing), emotional lability, high feeling, and abnormal thinking. The frequency and intensity of adverse events increased with increasing CI-977 dose. In conclusion, CI-977 Cmax and AUC(0-infinity) increased in proportion to dose over the range of 5 to 25 micrograms; decreases in negative free water clearance were related to CI-977 dose and Cmax and AUC(0-4 hr) values; and the frequency and intensity of adverse events increased with increasing CI-977 dose.

Topics: Adult; Benzofurans; Cross-Over Studies; Diuretics; Double-Blind Method; Female; Humans; Male; Middle Aged; Pyrrolidines; Receptors, Opioid, kappa

Pyrazole compounds are an intriguing class of compounds with potential analgesic activity; however, their mechanism of action remains unknown. Thus, the goal of this study was to explore the antinociceptive potential, safety and mechanism of action of novel 1-pyrazole methyl ester derivatives, which were designed by molecular simplification, using in vivo and in vitro methods in mice. First, tree 1-pyrazole methyl ester derivatives (DMPE, MPFE, and MPCIE) were tested in the capsaicin test and all presented antinociceptive effect; however the MPClE (methyl 5-trichloromethyl-3-methyl-1H-pyrazole-1-carboxylate) was the most effective. Thus, we selected this compound to assess the effects and mechanisms in subsequent pain models. MPCIE produced antinociception when administered by oral, intraperitoneal, intrathecal and intraplantar routes and was effective in the capsaicin and the acetic acid-induced nociception tests. Moreover, this compound reduced the hyperalgesia in diverse clinically-relevant pain models, including postoperative, inflammatory, and neuropathic nociception in mice. The antinociception produced by orally administered MPClE was mediated by κ-opioid receptors, since these effects were prevented by systemically pre-treatment with naloxone and the κ-opioid receptor antagonist nor-binaltorphimine. Moreover, MPCIE prevented binding of the κ-opioid ligand [(3)H]-CI-977 in vitro (IC₅₀ of 0.68 (0.32-1.4) μM), but not the TRPV1 ([(3)H]-resiniferatoxin) or the α₂-adrenoreceptor ([(3)H]-idazoxan) binding. Regarding the drug-induced side effects, oral administration of MPClE did not produce sedation, constipation or motor impairment at its active dose. In addition, MPCIE was readily absorbed after oral administration. Taken together, these results demonstrate that MPClE is a novel, potent, orally active and safe analgesic drug that targets κ-opioid receptors.

Topics: Adrenergic alpha-2 Receptor Antagonists; Analgesics; Animals; Benzofurans; Diterpenes; Drug Administration Routes; Drug Evaluation, Preclinical; Idazoxan; Male; Mice; Molecular Structure; Naloxone; Naltrexone; Narcotic Antagonists; Pain Measurement; Pyrazoles; Pyrrolidines; Radioligand Assay; Receptors, Opioid, kappa; Tritium; TRPV Cation Channels

Kappa agonists can attenuate reinstatement of cocaine-seeking behavior induced by cocaine priming. The mechanisms underlying this effect have not been characterized fully but may have a serotonergic component as kappa agonists also increase the release of serotonin (5-hydroxytryptamine, 5-HT).. This study investigated the role of kappa opioid receptor and 5-HT mechanisms in kappa agonist-induced attenuation of cocaine priming in monkeys.. Squirrel monkeys were trained to self-administer cocaine (0.18-0.3 mg/kg/injection) under a second-order schedule in which drug seeking was maintained jointly by cocaine injections and a cocaine-paired visual stimulus. In extinction sessions, saline was substituted for cocaine, and the cocaine-paired stimulus was omitted. During test sessions, only saline was available for self-administration, and response-contingent presentations of the cocaine-paired stimulus were restored.. Priming injections of cocaine (0.1-1.0 mg/kg) induced reinstatement of drug seeking. Maximal levels of responding were similar to those maintained by active cocaine self-administration. Pretreatment with the kappa agonists enadoline (0.01 mg/kg) and spiradoline (0.3 mg/kg) or the 5-HT transport inhibitors fluoxetine (5.6 mg/kg) and citalopram (10.0 mg/kg) attenuated the priming effects of cocaine, shifting the cocaine dose-response function rightward and downward. Inhibition of cocaine-induced reinstatement of drug seeking by spiradoline and fluoxetine was reversed by R(+)8-hydroxy-2-(di-n-propylamino)tetralin (0.03 mg/kg), a 5HT(1A) agonist that inhibits 5-HT release. The effects of spiradoline also were reversed by the kappa antagonist nor-binaltorphimine (10.0 mg/kg).. Results suggest that the capacity of kappa opioid agonists to increase extracellular 5-HT levels may at least partially underlie kappa agonist-induced modulation of cocaine seeking.

Topics: Animals; Benzofurans; Citalopram; Cocaine-Related Disorders; Dose-Response Relationship, Drug; Fluoxetine; Ligands; Naltrexone; Pyrrolidines; Receptors, Opioid, kappa; Saimiri; Selective Serotonin Reuptake Inhibitors; Self Administration; Serotonin; Serotonin 5-HT1 Receptor Agonists

There is evidence showing that the opioid systems play an important role in cocaine addiction; fewer studies have examined their roles in cocaine withdrawal. This study was conducted to determine whether cocaine or chronic withdrawal from cocaine alters the receptor component of the kappa-opioid system. Male Fischer rats were injected with saline or cocaine (3x15 mg/kg/day for 4 days, 3x20 mg/kg/day for 4 days, 3x25 mg/kg/day for 4 days, and 3x30 mg/kg/day for 2 days), three times daily at 1-h intervals in an escalating dose paradigm for 14 days. Identically treated rats were withdrawn from cocaine or saline for 14 days. We performed quantitative autoradiographic mapping of kappa-opioid receptors (KOP-r) in the brains of rats treated with this escalating dose "binge" cocaine administration paradigm and of rats withdrawn from cocaine for 14 days. A significant condition (chronic/withdrawal) effect was shown across all regions analyzed. A significant increase in [3H]CI-977 binding to KOP-r was detected in the septum of rats treated with an escalating dose binge cocaine administration paradigm and killed 30 min after the last cocaine injection. In contrast, there was a decrease in KOP-r binding in the septum and the basolateral amygdala of rats withdrawn for 14 days from chronic escalating dose binge cocaine administration, compared to rats at the end of 14 days chronic escalating dose cocaine administration. These results reconfirm and extend that KOP-r undergoes upregulation in response to chronic binge cocaine administration here, with an escalating dose. The observed lowering in KOP-r binding, which was shown in two brain regions of cocaine withdrawn animals, might contribute to the persistent dysphoria reported a long time after the discontinuation of the drug.

Topics: Amygdala; Analysis of Variance; Animals; Autoradiography; Behavior, Animal; Benzofurans; Cocaine; Cocaine-Related Disorders; Dopamine Uptake Inhibitors; Down-Regulation; Drug Administration Schedule; Male; Neuroprotective Agents; Pyrrolidines; Rats; Rats, Inbred F344; Receptors, Opioid, kappa; Septum of Brain; Tritium

Kappa opioid agonists were at one time proposed as candidate pharmacotherapies for cocaine addiction, mainly because of their ability to decrease dopamine neurotransmission and attenuate the behavioral effects of cocaine in laboratory animals. Recent studies, however, suggest that kappa agonists also may mimic and/or enhance some of the effects of cocaine through mechanisms related to stress. The current study used a reinstatement procedure to examine the ability of the kappa agonists spiradoline and enadoline to reinstate extinguished cocaine seeking in squirrel monkeys previously trained to self-administer cocaine under a second-order schedule of i.v. drug injection. Opioid- and stress-related mechanisms were evaluated in antagonism studies with the opioid antagonists naltrexone and nor-binaltorphimine (nor-BNI), the corticotropin-releasing factor receptor antagonist butyl-ethyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo [2,3-d]pyrimidin-4-yl]amine (CP 154,526), and the alpha(2)-adrenoceptor agonist clonidine combined with either spiradoline or enadoline. When tested alone, priming with spiradoline and enadoline induced significant reinstatement of cocaine-seeking behavior to approximately 45% of the maximum reinstatement induced by cocaine. Reinstatement of cocaine seeking induced by intermediate doses of spiradoline was greater in the presence than in the absence of response-contingent presentations of a cocaine-paired stimulus. Spiradoline- and enadoline-induced reinstatement of drug seeking was attenuated by naltrexone but not by nor-BNI. Spiradoline-induced reinstatement of cocaine seeking was also antagonized by CP 154,526 and clonidine. The results point to interactions between a subpopulation of kappa opioid receptors and central corticotropin-releasing factor and noradrenergic stress systems in the reinstatement of cocaine seeking induced by kappa agonists.

Topics: Animals; Behavior, Addictive; Benzofurans; Clonidine; Cocaine-Related Disorders; Corticotropin-Releasing Hormone; Male; Naltrexone; Norepinephrine; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Saimiri; Self Administration; Stress, Psychological

As kappa agonists have been proposed as treatments for cocaine abuse, the cardiovascular effects of the kappa opioid receptor agonists ethylketocyclazocine (EKC) and enadoline were investigated in conscious squirrel monkeys. Both EKC and enadoline increased heart rate with little effect on blood pressure. This effect appeared to be specific for kappa receptors as the mu opioid agonist morphine did not mimic the effects of the kappa agonists. The opioid antagonist naltrexone, at a dose of 1.0 mg/kg, blocked the effect of EKC. An action at both central and peripheral receptors may be responsible for the heart rate increase following kappa agonist treatment. The ganglionic blocker chlorisondamine partially antagonized the effect of EKC on heart rate, suggesting central involvement, while the peripherally-acting agonist ICI 204,448 ((+/-)-1-[2,3- (Dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride) also increased heart rate, supporting a peripheral site of action. When given in combination with cocaine, EKC produced effects that were sub-additive, suggesting that the kappa agonists may be used safely as cocaine abuse treatments.

Topics: Animals; Benzofurans; Blood Pressure; Cocaine; Cocaine-Related Disorders; Drug Interactions; Ethylketocyclazocine; Heart Rate; Male; Pyrrolidines; Receptors, Opioid, kappa; Saimiri

The supraspinal and spinal antinociceptive effects of several kappa-opioid receptor agonists were examined in diabetic and non-diabetic mice using the tail-flick assay. The antinociception induced by intrathecal (i.t.), but not intracerebroventricular (i.c.v.), CI-977, a highly selective kappa(1)-opioid receptor agonist, in diabetic mice was less than that in non-diabetic mice. The antinociceptive effects of ICI-199,441 and R-84760, high potency kappa(1)-opioid receptor agonists, given i.c.v., but not i.t., were attenuated in diabetic mice compared to those in non-diabetic mice. On the other hand, the antinociceptive effects of the new kappa-opioid receptor agonist TRK-820, which has high affinity for kappa(2)- and/or kappa(3)-opioid receptors, injected both i.c.v. and i.t. in diabetic mice were markedly less than those in non-diabetic mice. These results indicate that the antinociceptive effects of those kappa-opioid receptor agonists in diabetic mice are altered in a region-specific manner in the central nervous system (CNS). The dysfunction of kappa-opioid receptor subtypes in diabetic mice may underlie this CNS region-specific variation in the effects of these kappa-opioid receptor agonists.

Topics: Analgesics; Animals; Benzofurans; Brain; Diabetes Mellitus, Experimental; Dose-Response Relationship, Drug; Male; Mice; Mice, Inbred ICR; Pain Measurement; Pyrrolidines; Receptors, Opioid, kappa; Spinal Cord

Short periods of maternal separation of neonatal rats are known to induce attenuated behavioural and neuroendocrine responses to stress in adult life. The present study was carried out to evaluate whether 15 min separation from the dam during postnatal days 1-21 (MS15) can induce long-term changes in brain opioid (kappa- and delta-receptors) and opioid receptor-like 1 (ORL1) densities in male Sprague-Dawley rats. Receptor autoradiography indicated that MS15 rats had increased delta-receptor density in the basomedial amygdala compared to animal facility reared rats 2 months after MS15. No differences in brain kappa- or ORL1-receptor density were found. The results indicate that a manipulation early in life can induce persistent neurochemical changes in the delta-opioid receptor system, which suggests involvement of delta-opioid receptors in the altered emotional processing in these rats.

Topics: Animals; Animals, Newborn; Autoradiography; Benzofurans; Binding Sites; Brain; Cell Count; Female; Male; Maternal Deprivation; Nociceptin; Nociceptin Receptor; Oligopeptides; Opioid Peptides; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Time Factors; Tritium

Using quantitative receptor autoradiography we have determined if deletion of the delta-opioid receptor gene (Oprd1) results in compensatory changes in the expression of other opioid receptors. Gene targeting was used to delete exon 1 of the mouse delta-opioid receptor gene and autoradiography was carried out on brains from wild-type, heterozygous and homozygous knockout mice. Delta-opioid receptors were labeled with [(3)H]deltorphin I (7 nM), mu- with [(3)H]DAMGO (4 nM), and kappa- with [(3)H]CI-977 (2.5 nM) or [(3)H]bremazocine (2 nM in the presence of DPDPE and DAMGO) and non-specific binding determined with naloxone. [(3)H]Deltorphin I binding was reduced by approximately 50% in heterozygous animals. In homozygous animals specific binding could only be detected after long-term film exposure (12 weeks). Regions exhibiting this residual [(3)H]deltorphin I binding correlated significantly with those demonstrating high levels of the mu-receptor and were abolished in the presence of the mu-agonist DAMGO. Autoradiographic mapping showed significant overall reductions in [(3)H]DAMGO and [(3)H]CI-977 binding throughout the brain following loss of both copies of the Oprd1 gene. In contrast, overall levels of [(3)H]bremazocine binding were higher in brains from -/- than +/+ mice. Our findings suggest that residual [(3)H]deltorphin I binding in the brain of delta-receptor gene knockout mice is the result of cross-reactivity with mu-sites and that there are no delta-receptor subtypes derived from a different gene. Changes in mu- and kappa-receptor labeling suggest compensatory changes in these subtypes in response to the absence of the delta-receptor. The differences in [(3)H]CI-977 and [(3)H]bremazocine binding indicate these ligands show differential recognition of the kappa-receptor.

Topics: Animals; Autoradiography; Benzofurans; Benzomorphans; Brain; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Female; Heterozygote; Homozygote; Male; Mice; Mice, Knockout; Oligopeptides; Pyrrolidines; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu

Recent studies indicate that sex and rodent strain are determinants of sensitivity to opioid-induced antinociception.. The present study examined the influence of sex and rat strain on kappa opioid-induced antinociception using a series of kappa opioids that vary in their relative effectiveness.. In a warm-water (50, 52 and 55C) tail-withdrawal procedure, the antinociceptive effects of kappa opioids were determined in male and female rats of the F344, Lewis and Sprague-Dawley (SD) strains.. In both males and females of each strain, spiradoline produced high levels of antinociception across all nociceptive stimulus intensities, whereas U50,488 produced high levels only at the low and moderate nociceptive stimulus intensities. Sex differences in the potency and effectiveness of these kappa opioids were relatively small and not consistently obtained. Enadoline, bremazocine and nalorphine were less effective than spiradoline in producing antinociception, and at low and moderate nociceptive stimulus intensities these opioids were both more potent and effective in F344 and SD males than their female counterparts. In contrast, in Lewis rats, only bremazocine was more potent and effective in males. In combination tests, bremazocine shifted the spiradoline dose-effect curve leftward and/or upward in males and rightward in females (i.e., antagonized spiradoline). In contrast, in both males and females enadoline shifted the spiradoline dose-effect curve leftward and/or upward.. These data indicate that kappa opioids were generally more potent and effective as antinociceptive agents in males than females. Similar to data obtained with micro opioids, the magnitude of these sex differences was generally larger with the less effective kappa opioids and determined, in part, by rat strain and nociceptive stimulus intensity.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzofurans; Benzomorphans; Female; Male; Nalorphine; Narcotics; Pyrrolidines; Rats; Rats, Inbred F344; Rats, Inbred Lew; Rats, Inbred Strains; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Sex Characteristics

Squirrel monkeys were trained to discriminate i.m. injections of the kappa-opioid receptor agonist enadoline (0.0017 mg/kg) from saline in a two-lever drug-discrimination procedure. Enadoline produced a reliable discriminative stimulus that was reproduced by the kappa-selective agonists PD 117302, U 50,488, GR 89686A, (-)-spiradoline, ICI 204448, and EMD 61753, and by the mixed-action kappa/mu-agonists bremazocine and ethylketocyclazocine. The discriminative stimulus effects of enadoline were not reproduced by the mu-selective agonist morphine, the delta-selective agonist BW373U86, the mixed-action opioids nalbuphine and nalorphine, or by the less active enantiomers of enadoline and spiradoline PD 129829 and (+)-spiradoline, respectively. The selective mu-opioid antagonist beta-funaltrexamine (10.0 mg/kg) did not appreciably alter the dose-effect function for enadoline in any subject. However, the nonselective and kappa-selective opioid antagonists quadazocine (0.03-3.0 mg/kg) and nor-BNI (3-10 mg/kg), and the mixed-action opioid nalbuphine (0.3-30 mg/kg) served to surmountably antagonize enadoline's discriminative stimulus effects. The antagonist effects of nor-BNI were long-lasting and did not distinguish between drugs purported to act at different kappa-receptor subtypes. The present results bolster the view that common discriminative stimulus effects of enadoline and other opioids are mediated by kappa-agonist actions that are surmountably antagonized by nor-BNI in a long-lasting manner. The enadoline-antagonist effects of nalbuphine support the idea that it acts with low efficacy at kappa-opioid receptors.

Topics: Animals; Benzofurans; Discrimination Learning; Dose-Response Relationship, Drug; Male; Nalbuphine; Naltrexone; Narcotic Antagonists; Pyrroles; Pyrrolidines; Receptors, Opioid, kappa; Receptors, Opioid, mu; Saimiri; Thiophenes

Until recently the opioid receptor family was thought to consist of only the mu-, delta- and kappa-receptors. The cloning of opioid receptor like receptor (ORL1) and its endogenous ligand nociceptin/orphanin FQ, which displayed anti-opioid properties, has raised the issue of functional co-operativity of this system with the classical opioid system. ORL1 receptor knockout mice have been successfully developed by homologous recombination to allow the issue of potential heterogeneity of this receptor and also of compensatory changes in mu-, delta- or kappa-receptors in the absence of ORL1 to be addressed. We have carried out quantitative autoradiographic mapping of these receptors in the brains of mice that are wild-type, heterozygous and homozygous for the deletion of the ORL1 receptor. ORL1, mu-, delta- and kappa-receptors were labelled with [(3)H] leucyl-nociceptin (0.4 nM), [(3)H] DAMGO (4 nM), [(3)H] deltorphin-I (7 nM), and [(3)H] CI-977 (2.5 nM) respectively. An approximately 50% decrease in [(3)H] leucyl-nociceptin binding was seen in heterozygous ORL1 mutant mice and there was a complete absence of binding in homozygous brains indicating the single gene encodes for the ORL1 receptor and any putative subtypes. No significant gross changes in the binding to other opioid receptors were seen across genotypes in the ORL1 mutant mice demonstrating a lack of major compensation of classical opioid receptors in the absence of ORL1. There were a small number of region specific changes in the expression of classical opioid receptors that may relate to interdependent function with ORL1.

Topics: Analgesics, Opioid; Animals; Autoradiography; Benzofurans; Binding Sites; Brain; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Gene Deletion; Mice; Mice, Knockout; Neurons; Neuroprotective Agents; Nociceptin; Nociceptin Receptor; Oligopeptides; Opioid Peptides; Pyrrolidines; Radioligand Assay; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Tritium

It has been reported that the discriminative stimulus effects of cocaine in squirrel monkeys can be potentiated by mu opioid agonists and attenuated by kappa opioid agonists. The purpose of this study was to extend these observations by examining the effects of mu and kappa opioids agonists on the discriminative stimulus effects of d-amphetamine (AMPH). Five squirrel monkeys were trained to discriminate 0.3 mg/kg of AMPH (i.m.) from saline using a stimulus termination/avoidance task. AMPH and cocaine substituted dose dependently for the AMPH training stimulus in all five monkeys. The AMPH training dose was completely antagonized by 0.1 mg/kg of the D1 dopamine antagonist SCH 39166. When administered alone, the kappa agonist U69,593 substituted partially or completely for AMPH in four of five monkeys, the kappa agonist enadoline substituted completely for AMPH in two of five monkeys, and morphine substituted completely for AMPH in one monkey. In all five monkeys, pretreatment with some doses of U69,593 or enadoline attenuated the discriminative stimulus effects of AMPH; however, some doses of U69,593 and enadoline also potentiated the effects of AMPH in at least two monkeys. Morphine pretreatment potentiated the discriminative stimulus effects of AMPH in three monkeys and either attenuated or did not alter these effects in two monkeys. Morphine pretreatment did not significantly alter the discriminative stimulus effects of cocaine except in one monkey. These data indicate large individual differences in the abilities of mu and kappa opioid agonists to alter the discriminative stimulus effects of AMPH.

Topics: Animals; Benzeneacetamides; Benzofurans; Cocaine; Dextroamphetamine; Discrimination Learning; Dose-Response Relationship, Drug; Drug Interactions; Morphine; Pyrrolidines; Receptors, Opioid, kappa; Receptors, Opioid, mu; Saimiri

Opioid receptors are known to couple to G-proteins and to inhibit adenylyl cyclase. Receptor activation of G-proteins can be measured by agonist-stimulated [35S]guanylyl-5'-O-(gamma-thio)-triphosphate (GTP gamma S-) binding in brain sections to localize neuroanatomically functional coupling of receptors to intracellular signal transduction mechanisms. In the present study the selective mu-, delta- and kappa 1-opioid agonists DAMGO ([D-Ala2,N-Me-Phe4, Gly-ol5]-enkephalin), DPDPE ([D-Pen2,5]-enkephalin) and enadoline (CI-977) were used to stimulate [35S]GTP gamma S-binding in human brain sections of frontal cortex and cerebellum. In human frontal cortex mu- and delta- opioid stimulated [35S]GTP gamma S-binding was evenly distributed throughout the gray matter, while kappa(1)-opioid stimulated [35S]GTP gamma S-binding was detected predominantly in lamina V and VI. In the cerebellar cortex stimulated [35S]GTP gamma S-binding revealed functional coupling of mu- and kappa 1-opioid receptors in the molecular layer.

Topics: Autoradiography; Benzofurans; Cerebellum; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Frontal Lobe; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Male; Middle Aged; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Sulfur Radioisotopes

The ability of kappa-opioid receptor ligands to modulate dependence-related behavioural effects of drugs like morphine and cocaine is well documented. The present study examined the effects of kappa-opioid agonists on nicotine-induced locomotor stimulation in rats chronically pre-exposed to nicotine (0.4 mg/kg/day). U50,488 [0.5-3 mg/kg subcutaneously (s.c.)], U69,593 [0.08-0.32 mg/kg intraperitoneally (i.p.)] and CI-977 (0.005-0.02 mg/kg s.c.) administered 30 min prior to nicotine (0.06, 0.2 and 0.4 mg/kg s.c.) dose-dependently antagonised its acute locomotor-activating effect, which was completely prevented by the highest tested dose of each agonist. Baseline activity was unaffected by the largest doses of U50,488 and U69,593, but it was reduced by 0.01 and 0.02 mg/kg of CI-977. The selective kappa-opioid receptor antagonist nor-BNI [30 microg intracerebroventricularly (i.c.v.)] blocked the effects of U69,593 on nicotine-induced behaviour, thus supporting the involvement of kappa-opioid receptors in this effect. In conclusion, the activation of kappa-opioid receptors clearly prevented nicotine-induced locomotor stimulation. The effects of at least two of the kappa-opioid agonists were not due to a general motor suppression. It is suggested that the mechanism entails a depression of nicotine-induced increases in accumbal dopamine by these compounds. The results should encourage further research on the role of the kappa-opioid system in the behavioural and neurochemical effects of nicotine, including those related to nicotine dependence.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Behavior, Animal; Benzeneacetamides; Benzofurans; Dose-Response Relationship, Drug; Injections, Intraventricular; Male; Motor Activity; Naltrexone; Nicotine; Nicotinic Agonists; Pyrrolidines; Rats; Receptors, Opioid, kappa

The role of the dynorphin/kappa-opioid receptor system in ethanol reinforcement is unclear.. Examination of the effects of the highly selective kappa-opioid receptor agonist CI-977 (enadoline) and of the long-acting selective kappa-opioid receptor antagonist nor-binaltorphimine (nor-BNI) on relapse-like drinking measured by the alcohol deprivation effect (ADE) in long-term ethanol-experienced rats.. Rats were either implanted with mini-osmotic pumps delivering 0 or 0.01 mg/kg per h CI-977 or received two injections (12 h apart) of nor-BNI (0 or 5 mg/kg i.p.) before representation of alcohol after 2 weeks of alcohol deprivation in a four-bottle home cage drinking paradigm. In a second experiment, long-term ethanol-experienced rats trained in an operant ethanol self-administration paradigm received either acute CI-977 treatment (0, 0.003-0.1 mg/kg i.p.) or two injections (12 h apart) of nor-BNI (0 or 5 mg/kg i.p.) before a 23-h session.. Chronic CI-977 potentiated ethanol intake and preference during the ADE. Acute CI-977 dose-dependently reduced total lever pressing activity demonstrating an unspecific sedative effect, except for the lowest dose (0.003 mg/kg), which selectively increased lever pressing for ethanol during basal drinking. Nor-BNI did not affect relapse-like drinking at all.. Stimulation of kappa-opioid receptors can increase ethanol intake, at least in long-term ethanol-experienced rats. Since kappa-opioid receptor agonists have aversive motivational consequences, increased ethanol drinking might be an attempt to counteract the aversive effects of this treatment. On the other hand, the nor-BNI experiments indicate that endogenous kappa-opioid receptor stimulation does not seem to be involved in relapse-like drinking after protracted abstinence.

Topics: Alcohol Drinking; Animals; Benzofurans; Conditioning, Operant; Drinking; Eating; Male; Naltrexone; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa; Recurrence; Self Administration

The effects of a daily injection of the delta selective opioid antagonist naltrindole (1 mg/kg), from birth to postnatal day 19, on antinociceptive and behavioral responses to the mu selective agonist alfentanil (65 microg/kg) and the kappa selective agonist CI-977 (50 microg/kg) in 20-day-old male rats were investigated. Antinociception was assessed using the tail immersion test and behavioral testing was performed by employing an open field. The functional blockade of the delta receptor by naltrindole blocked the antinociceptive response to alfentanil but did not affect the antinociception induced by CI-977. The effects of alfentanil (increased exploration) and CI-977 (a marked hypoactivity) in the open field were not modified by neonatal naltrindole treatment. The results suggest a functional interaction between delta and mu receptors in the postnatal period but not between delta and kappa receptors. The data also suggest differences in the delta and mu receptors interacting in the modulation of antinociception and those involved in behavioral responses in the open field.

Topics: Alfentanil; Animals; Animals, Newborn; Benzofurans; Male; Naltrexone; Narcotic Antagonists; Narcotics; Pain Measurement; Psychomotor Performance; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu

Opioids are involved in the development of epileptic seizures. Recently, interest has been focused on the role of the kappa-opioid receptor agonists as novel approaches to the treatment of epilepsy. In the present study we investigated the effects of the kappa-opioid receptor agonist enadoline (Ena) on pentylenetetrazol (PTZ) induced seizures, PTZ kindling, shuttle-box performance and hippocampal neuromorphology. Ena injected i.c.v. in doses of 1 and 10 nmol did not affect acute PTZ seizures. In the course of PTZ kindling development, co-treatment (1 nmol) with the kappa-opioid receptor agonist suppressed seizure strength. Eight days after kindling completion the animals received a challenge dose of PTZ. In reaction to challenge, kindled animals which were pretreated with Ena reached significantly lower seizure scores. Kindling resulted in diminished shuttle-box performance. Learning performance in kindled animals pretreated with Ena was not normalised. Kindling resulted in increased glutamate binding. Interestingly, in comparison with the saline/saline group, neither in the Ena/saline nor in the Ena/PTZ treated groups changes in glutamate binding were found. That means that Ena prevented the increase in glutamate binding in the kindled group. In kindled animals significant cell loss in CA1 of the dorsal hippocampus was found and this was efficaciously counteracted by Ena. However, Ena alone did induce similar cell loss compared to kindled animals. It is hypothesised that the effects of enadoline are mainly due to interferences with glutamatergic systems.

Topics: Animals; Benzofurans; Convulsants; Glutamic Acid; Hippocampus; Kindling, Neurologic; Learning; Male; Pentylenetetrazole; Pyrrolidines; Rats; Rats, Wistar; Seizures

In mammals, opioids act by interactions with three distinct types of receptors: mu, delta, or kappa opioid receptors. Using a novel assay of antinociception in the Northern grass frog, Rana pipiens, previous work demonstrated that selective mu, delta, or kappa opioids produced a potent antinociception when administered by the spinal route. The relative potency of this effect was highly correlated to that found in mammals. Present studies employing selective opioid antagonists, beta-FNA, NTI, or nor-BNI demonstrated that, in general, these antagonists were not selective in the amphibian model. These data have implications for the functional evolution of opioid receptors in vertebrates and suggest that the tested mu, delta, and kappa opioids mediate antinociception via a single type of opioid receptor in amphibians, termed the unireceptor.

Topics: Acetic Acid; Analgesics; Animals; Benzofurans; Female; Injections, Spinal; Male; Naltrexone; Narcotic Antagonists; Oligopeptides; Pain Measurement; Pyrrolidines; Rana pipiens; Receptors, Opioid; Time Factors

kappa-Opioid receptor agonists (e.g., enadoline or U-50,488) increase the locomotor activity of preweanling rats, while the same drugs depress the locomotor activity of adults. Curiously, direct stimulation of dopamine (DA) D2-like receptors fully attenuates the U-50,488-induced locomotor activity of preweanling rats. The purpose of the present study was to determine whether indirect DA agonists (i.e., cocaine, methylphenidate, and amphetamine) would also attenuate U-50,488's behavioral effects. In two experiments, 17-day-old rats were injected with saline or U-50,488 (5 mg/kg, sc) and locomotor activity and stereotyped sniffing were assessed. After 20 min, the saline- and U-50,488-pretreated rats were injected with saline, cocaine (5, 10, or 20 mg/kg, i.p.), methylphenidate (10 or 20 mg/kg, i.p.), amphetamine (2.5 or 5 mg/kg, i.p.), or the direct D2-like receptor agonist NPA (1 mg/kg, i.p.). As expected, U-50,488 dramatically enhanced the locomotor activity of 17-day-old rats, while attenuating the stereotyped sniffing caused by indirect and direct DA agonists. All three indirect DA agonists augmented U-50,488's locomotor activating effects across the initial 10 min of testing and then activity declined to U-50,488 control values. Direct stimulation of DA receptors produced nearly opposite effects because NPA attenuated U-50,488-induced locomotor activity across the entire testing session. It is uncertain why direct and indirect DA agonists affected U-50,488-induced locomotor activity differently, but the relative amount of DA D1-like receptor activation is probably not responsible.

Topics: Age Factors; Amphetamine; Analysis of Variance; Animals; Behavior, Animal; Benzofurans; Cocaine; Dopamine Agonists; Drug Interactions; Female; Locomotion; Male; Methylphenidate; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Stereotyped Behavior

Enadoline is a highly selective and potent kappa-opioid receptor agonist. This report describes and compares the activities of enadoline and morphine in a rat model of postoperative pain. A 1 cm incision through the muscle and skin of the plantar surface of the right hind paw induced thermal hyperalgesia as well as static and dynamic allodynia lasting at least 2 days. Postoperative testing was carried out using the plantar test for thermal hyperalgesia, von Frey hairs for static allodynia and light stroking with a cotton bud for dynamic allodynia. A single i.v. dose of enadoline 15 min before surgery dose-dependently (1-100 microg/kg) blocked the development of thermal hyperalgesia as well as static and dynamic allodynia for over 24 h with respective MEDs of < or = 1, 10 and 10 microg/kg. The administration of enadoline (100 microg/kg, i.v.), 1 h after surgery, completely blocked the maintenance of the hyperalgesic and allodynic responses, but its duration of action was much shorter (2 h) than when administered before surgery. Previous studies have shown that administration of morphine (1-6 mg/kg, s.c.) 0.5 h before surgery can prevent the development of thermal hyperalgesia with a MED of < or =1 mg/kg, but it has little effect on static allodynia. In the present study similar administration of morphine (1-3 mg/kg), unlike enadoline, had no effect on the development of dynamic allodynia. Morphine dose-dependently (1-6 mg/kg, s.c.) potentiated isoflurane-induced sleeping time and respiratory depression in the rat. However, whilst enadoline also (1-1000 microg/kg, i.v.) potentiated isoflurane-induced sleeping time, it did not cause respiratory depression. It is suggested that enadoline may possess therapeutic potential as a pre-emptive antihyperalgesic and antiallodynic agent.

Topics: Anesthesia Recovery Period; Animals; Benzofurans; Blood Gas Analysis; Disease Models, Animal; Hot Temperature; Hyperalgesia; Male; Morphine; Pain, Postoperative; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Respiratory Mechanics; Skin; Touch

A new rat model was established up to evaluate the antinociceptive effect of compounds in visceral pain. The test consisted in measuring the performance of rats in an aversive light stimulus avoidance experimental device. Rats with TNBS-induced colitis had a lower number of total active lever pressings and did not discriminate the active lever from the inactive one. Morphine (1 mg/kg, s.c.) and CI-977 (0.001 mg/kg, s.c.) treatment restored the level of pressing activity of animals and their ability to discriminate the active lever from the inactive one. Naloxone treatment antagonized the improvement of performance produced by morphine. The results obtained indicate that this behavioral paradigm may be used to evaluate the antinociceptive potential of compounds.

Topics: Analgesics, Opioid; Animals; Behavior, Animal; Benzofurans; Cognition; Colitis; Colon; Discrimination, Psychological; Male; Morphine; Pain; Pyrrolidines; Rats; Rats, Sprague-Dawley; Trinitrobenzenesulfonic Acid; Viscera

The modulation of depolarization (4-aminopyridine, 2 mM)-evoked endogenous glutamate release by kappa-opioid receptor activation and blockade of voltage-dependent Ca2+ -channels has been investigated in synaptosomes prepared from rat and marmoset striatum. 4-Aminopyridine (4-AP)-stimulated, Ca2+ -dependent glutamate release was inhibited by enadoline, a selective kappa-opioid receptor agonist, in a concentration-dependent and norbinaltorphimine (nor-BNI, selective kappa-opioid receptor antagonist)-sensitive manner in rat (IC50 = 4.4+/-0.4 microM) and marmoset (IC50 = 2.9+/-0.7 microM) striatal synaptosomes. However, in the marmoset, there was a significant (approximately 23%) nor-BNI-insensitive component. In rat striatal synaptosomes, the Ca2+ -channel antagonists omega-agatoxin-IVA (P/Q-type blocker), omega-conotoxin-MVIIC (N/P/Q-type blocker) and omega-conotoxin-GVIA (N-type blocker) reduced 4-AP-stimulated, Ca2+ -dependent glutamate release in a concentration-dependent manner with IC50 values of 6.5+/-0.9 nM, 75.5+5.9 nM and 106.5+/-8.7 nM, respectively. In marmoset striatal synaptosomes, 4-AP-stimulated, Ca2+ -dependent glutamate release was significantly inhibited by omega-agatoxin-IVA (30 nM, 57.6+/-2.3%, inhibition), omega-conotoxin-MVIIC (300 nM, 57.8+/-3.1%) and omega-conotoxin-GVIA (1 microM, 56.7+/-2%). Studies utilizing combinations of Ca2+ -channel antagonists suggests that in the rat striatum, two relatively distinct pools of glutamate, released by activation of either P or Q-type Ca2+ -channels, exist. In contrast, in the primate there is much overlap between the glutamate released by P and Q-type Ca2+ -channel activation. Studies using combinations of enadoline and the Ca2+ -channel antagonists suggest that enadoline-induced inhibition of glutamate release occurs primarily via reduction of Ca2+ -influx through P-type Ca2+ -channels in the rat but via N-type Ca2+ -channels in the marmoset. In conclusion, the results presented suggest that there are species differences in the control of glutamate release by kappa-opioid receptors and Ca2+ -channels.

Topics: 4-Aminopyridine; Animals; Benzofurans; Calcium Channel Blockers; Calcium Channels; Callithrix; Glutamic Acid; In Vitro Techniques; Male; Naltrexone; Narcotic Antagonists; Neostriatum; omega-Agatoxin IVA; omega-Conotoxin GVIA; Peptides; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Spider Venoms; Synaptosomes; Tetrodotoxin

Eight kappa-opioid receptor agonists were examined for their effects in squirrel monkeys responding under a fixed interval 3-min schedule of stimulus termination. Six of these kappa-opioid receptor agonists decreased dose-dependently the total number of responses and with an order of potency consistent with kappa-opioid receptor interaction. Three of these kappa-opioid receptor agonists, bremazocine, U69,593 [[(5a,7a,8b)-(+)-N-[7-(1-pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl)] benzeneacetamide] and enadoline, were evaluated following pretreatment with 1.0 mg/kg of naltrexone or 3.0 mg/kg of norbinaltorphimine. The effects of the three agonists were antagonized significantly by naltrexone, but only those of bremazocine and U69,593 were antagonized significantly by norbinaltorphimine. Statistical analysis of the data averaged over six monkeys revealed that naltrexone was significantly more potent than norbinaltorphimine at antagonizing enadoline and U69,593, but naltrexone and norbinaltorphimine were equipotent at antagonizing bremazocine. Moreover, naltrexone was 8-fold more potent at antagonizing U69,593 and enadoline than at antagonizing bremazocine. These results suggest that under these conditions the effects of U69,593 and enadoline may be mediated, in part, by a different receptor population, perhaps a subtype of kappa-opioid receptors, from the one that mediates the effects of bremazocine.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Behavior, Animal; Benzeneacetamides; Benzofurans; Benzomorphans; Conditioning, Operant; Dose-Response Relationship, Drug; Ethylketocyclazocine; Nalorphine; Naltrexone; Narcotic Antagonists; Pyrroles; Pyrrolidines; Receptors, Opioid, kappa; Reinforcement Schedule; Saimiri; Thiophenes

1. The treatment of Parkinson's disease relies predominantly upon dopamine replacement therapy, usually with l-dihydroxyphenylalanine (L-DOPA). However, side-effects of long-term treatment, such as L-DOPA-induced dyskinesias can be more debilitating than the disease itself. Non-dopaminergic treatment strategies might therefore be advantageous. 2. The aim of this study was to investigate the potential anti-parkinsonian efficacy of the kappa-opioid receptor agonist, enadoline, and the alpha-adrenoreceptor agonist, clonidine, both alone or in combination, in the reserpine-treated rat model of Parkinson's disease. 3. Rats were treated with reserpine (3 mg kg-1), and experiments carried out 18 h later, at which time they exhibited profound akinesia (normal animals 1251+/-228 mobile counts h-1, reserpine-treated animals 9+/-2 mobile counts h-1). Both enadoline and clonidine increased locomotion in reserpine-treated rats in a dose-dependent manner. The maximum locomotor-stimulating effect of enadoline alone was seen at a dose of 0.2 mg kg-1 (208+/-63 mobile counts h-1). The maximum effect of clonidine was seen at a dose of 2 mg kg-1 (536+/-184 mobile counts h-1). 4. Co-administration of enadoline (0.1 mg kg-1) and clonidine (0.01 - 0.1 mg kg-1) at sub-threshold doses, synergistically increased locomotion. 5. The synergistic stimulation of locomotion in the reserpine-treated rat involved activation of kappa-opioid receptors and a combination of both alpha1 and alpha2-adrenoreceptors. 6. The results presented suggest a need for further studies on the potential of stimulating kappa-opioid and/or alpha-adrenoreceptors as a therapy for Parkinson's disease. Furthermore, the studies may offer potential mechanistic explanations of the ability of alpha2-adrenergic receptor antagonist to reduce L-DOPA-induced dyskinesia in Parkinson's disease.

Topics: Adrenergic alpha-Agonists; Adrenergic alpha-Antagonists; Animals; Antiparkinson Agents; Benzofurans; Biogenic Monoamines; Clonidine; Disease Models, Animal; Drug Combinations; Drug Synergism; Locomotion; Male; Naltrexone; Narcotic Antagonists; Parkinson Disease, Secondary; Prazosin; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Reserpine; Yohimbine

Nociceptin is an endogenous ligand of the opioid receptor-like (ORL1) receptor, a G-protein coupled receptor with sequence similarities to the opioid receptors. ORL1 receptors are present at both central and peripheral sites in several mammalian species but their functions are as yet poorly understood. The main aim of this investigation was to study the effects of nociceptin and the putative ORL1 receptor antagonist [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) in two peripheral tissues, the isolated proximal colon of the mouse and the distal colon of the rat. Nociceptin, [D-Ala(2), MePhe(4), Gly-ol(5)]enkephalin (DAMGO; mu-opioid receptor selective) and [D-Pen(2), D-Pen(5)]enkephalin (DPDPE; delta-opioid receptor selective) caused concentration-dependent contractions of mouse and rat isolated colon preparations (nociceptin EC(50)=1.20 and 0.28 nM in the mouse and rat, respectively). Des[Phe(1)]nociceptin (250 nM) had no contractile effect. Naloxone (300 nM) antagonised the effects of DAMGO and DPDPE but had no effect in either preparation on contractions seen in response to nociceptin. [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) also caused contractions in the colonic preparations (EC(50)=6.0 and 3.1 nM in the mouse and rat, respectively); there was no evidence of any antagonist activity. Tetrodotoxin (1 microM) abolished the contractile effects of nociceptin in the mouse colon but had no effect in the rat. In the vas deferens preparation isolated from DBA/2 mice, nociceptin caused concentration-dependent inhibitions of electrically-evoked contractions which were antagonised by [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) (apparent pK(B)=6. 31). However, [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) (0.3-10 microM) also possessed agonist activity in this preparation, as it inhibited the electrically-evoked contractions in a concentration-dependent manner. These observations do not support the proposal that [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) has agonist activity at central ORL1 receptors but is an antagonist in the periphery and that these differences in efficacy point to differences in the receptors. Rather, these data along with those of others suggest that [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) is a partial agonist and that differences in receptor reserve can account for the varied pharmacological actions of this pseudopeptide at central and peripheral sites.

Topics: Animals; Benzeneacetamides; Benzofurans; Colon; Dose-Response Relationship, Drug; Electric Stimulation; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; In Vitro Techniques; Ligands; Male; Mice; Mice, Inbred DBA; Muscle Contraction; Narcotic Antagonists; Nociceptin; Nociceptin Receptor; Opioid Peptides; Peptide Fragments; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Tetrodotoxin; Vas Deferens

This study investigated whether peptides acting at somatostatin receptors, such as somatostatin-14, octreotide or cortistatin-14, can influence the extent of brain damage after focal ischaemia in rats. The intracerebroventricular application of 0.1 or 1.0 nmol somatostatin-14 5 min after middle cerebral artery occlusion significantly reduced the infarct size assessed 7 days after the insult (by 47% and 57% of the saline control), whereas 10.0 nmol had no significant protective effect (9% reduction). A similar dose/response relationship was obtained after intracerebroventricular injection of octreotide. The lower doses of 0.1 or 1.0 nmol afforded significant neuroprotection (reduction of the infarct size by 72 and 57%), whereas 10 nmol actually increased the infarct size up to 348%. Cortistatin-14 (10 nmol) decreased the ischaemic damage by 52%. For comparison with the neuropeptides acting on somatostatin receptors, the kappa opiate agonist enadoline (10 nmol) also had a significant protective effect against the development of focal ischaemia; the extent of the brain damage was reduced by 60% after intracerebroventricular injection.

Topics: Animals; Benzofurans; Body Temperature; Brain Ischemia; Cerebral Cortex; Corpus Striatum; Hormones; Injections, Intraventricular; Male; Middle Cerebral Artery; Neurons; Neuropeptides; Neuroprotective Agents; Octreotide; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa; Somatostatin

A rat brain microdialysis study of enadoline (CI-977), a k-opioid agonist, was conducted in nonanesthetized healthy rats to determine brain extracellular fluid (ECF) concentrations of CI-977 associated with neuroprotective subcutaneous (s.c.) doses. Three groups of 3 to 4 nonanesthetized yet restrained Sprague-Dawley rats with jugular cannulas and implanted brain (striatum) microdialysis probes received single s.c. doses of 0.3, 1.0, or 3.0 mg/kg CI-977. Blood and microdialysate samples were collected over a 12-hour period. Extent of rat plasma protein binding was 77.5%. Unbound plasma concentrations associated with neuroprotection were 10-50 ng eq/mL. At each dose, brain ECF concentration-time profiles (corrected for probe recovery) were nearly coincident with enadoline plasma unbound concentration-time profiles. Consequently, at each dose the ratio of AUCecf/AUCffplasma, (AUC = Area Under the concentration-time Curve; ffplasma = free fraction in plasma = unbound plasma) which represents the distribution of drug between plasma and brain, was determined to be unity within experimental error. These results suggest that unbound plasma concentrations may predict brain ECF concentrations of CI-977. Further, our findings allow us to postulate enadoline unbound brain ECF concentrations necessary for neuroprotection.

Topics: Animals; Benzofurans; Binding, Competitive; Brain; Extracellular Space; Microdialysis; Neuroprotective Agents; Plasma; Prospective Studies; Pyrrolidines; Radioimmunoassay; Rats; Rats, Sprague-Dawley

Excessive glutamate transmission in the basal ganglia is a major factor in the neural mechanisms underlying parkinsonian akinesia. Activation of kappa opioid receptors causes a presynaptic reduction in glutamate release. Kappa opioid receptors are concentrated in those regions of the basal ganglia associated with increased glutamate transmission in parkinsonism. In this study, we use the alpha-methyl-p-tyrosine and reserpine-treated rat model of parkinsonism to investigate whether systemic administration of the kappa opioid agonists enadoline (CI-977) and U69,593 can alleviate the symptoms of parkinsonism either alone or in conjunction with dopamine replacement therapy. We report that, when administered alone, both enadoline and U69,593 can increase locomotion in monoamine-depleted rats. No increase in locomotor activity was seen after kappa opioid agonist administration in non-parkinsonian rats. The responses to kappa opioid agonists were blocked by co-administration of either the nonspecific opioid receptor antagonist naloxone or the selective kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI). An important finding is that when enadoline and L-dopa are administered together, their anti-akinetic properties are synergistic. Thus, the doses of enadoline and L-dopa required to alleviate akinesia when administered together are lower than either administered alone. These data illustrate the importance of kappa opioid receptors in the neural mechanisms controlling voluntary movement and suggest that kappa opioid agonists may have a role as adjuncts to dopamine replacement in the management of Parkinson's disease.

Topics: alpha-Methyltyrosine; Animals; Antiparkinson Agents; Benzeneacetamides; Benzofurans; Dose-Response Relationship, Drug; Drug Synergism; Levodopa; Male; Motor Activity; Parkinson Disease, Secondary; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Reserpine

The binding characteristics of the kappa opioid ligands [3H]U69,593 and [3H]bremazocine, the mu opioid ligand [3H][D-ala2,N-Me-Phe4,glycol5]enkephalin and the delta opioid ligand [3H]p-Cl-[D-pen2,5]enkephalin were studied in rhesus monkey brain membranes in saturation binding experiments and were followed by competition binding experiments with a variety of peptidic and nonpeptidic opioid ligands. The [3H]U69,593 sites appeared to be a subset of kappa opioid receptors (kappa-1 receptors: Kd, 1.2 nM; Bmax, 66 fmol/mg). [3H]Bremazocine (in the presence of mu and delta receptor-masking agents), bound to a larger population of kappa receptors (kappa-all: Kd, 0.39 nM; Bmax, 227 fmol/mg), which presumably included the aforementioned kappa-1 sites. Competition binding experiments revealed that the presently defined kappa-1 sites were similar to previously reported sites in other mammalian species, particularly in terms of the higher kappa-1 selectivity observed with arylacetamide (e.g., U50,488) vs. benzomorphan kappa agonists (e.g., ethylketocyclazocine). The kappa-selective antagonist norbinaltorphimine (nor-BNI) displayed a very small (2.3-fold) selectivity for kappa-1 vs. kappa-all sites. This led to the prediction that in rhesus monkeys (n = 3), systemically administered nor-BNI (10 mg/kg s.c.) should have a very moderate degree of antagonist selectivity for the antinociceptive effects of a putative kappa-1-agonist, the arylacetamide U50,488 (0.1-3.2 mg/kg s.c.), vs. those of the benzomorphan kappa agonist ethylketocyclazocine (0.01-056 mg/kg s.c.). This prediction was confirmed in vivo because nor-BNI (10 mg/kg) caused a robust and long lasting (up to 21 days) antagonism of the antinociceptive effects of U50,488 and a small but significant antagonism of ethylketocyclazocine. The arylacetamide congener Cl-977 (enadoline), which displayed an 11-fold kappa-1 vs. kappa-all binding selectivity, was not sensitive to nor-BNI pretreatment. This indicates that the kappa subtype-binding profile of an agonist is not necessarily predictive of its sensitivity to nor-BNI in vivo. Overall, the present results suggest that at least two functional kappa receptor populations may be present in rhesus monkey brain.

Topics: Analgesics, Opioid; Animals; Benzofurans; Brain Chemistry; Butorphanol; Dose-Response Relationship, Drug; Hot Temperature; Macaca mulatta; Nalbuphine; Naltrexone; Pyrrolidines; Radioligand Assay; Receptors, Opioid, kappa

The present study aimed to compare the actions of the selective kappa opioid receptor agonist enadoline (CI-977) with morphine in order to see if there is a heterogeneity of opioid receptors between spinal reflex pathways. High (C- and A-fibre evoked activity) and low (A-fibres only) intensity electrical stimulation of dorsal roots in the neonatal rat hemisected spinal cord preparation in vitro was used to distinguish between synaptic activity measured in the corresponding ventral root. Enadoline selectively depressed the high intensity-evoked EPSP with an EC50 of 7.6 nM (n = 7), contrasting with our previous finding in this preparation that morphine is an equipotent depressant of A- and C-fibre-mediated synaptic responses. The depressant effects of enadoline and morphine were reversed by naloxone giving apparent Kd values of 14 +/- 3 nM (n = 4) for enadoline-induced and 4.2 +/- 1 nM (n = 4) for morphine-induced depression. These data suggest that activation of kappa opioid receptors has a selective depressant action on C-fibre-mediated synaptic activity. Such a functional difference mediated at a subclass of opioid receptors has not been previously observed in an in vitro spinal preparation.

Topics: Animals; Animals, Newborn; Benzofurans; In Vitro Techniques; Morphine; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Spinal Cord

This work has explored the relationship between excitotoxicity and the amyloid precursor protein gene (APP) which may be relevant to future therapeutic developments in Alzheimer's disease. The excitotoxic effects of kainic acid (KA) and pentylenetetrazole (PTZ) have been compared and contrasted on the two major mRNA isoforms of APP using in situ hybridization and quantitative analysis of gene expression in rat brain. The Kunitz Protease Inhibitor containing isoform APP 770 KPI+, the major glial cell isoform, has been shown to be stimulated after KA and was related to neuronal loss and astrocyte activation as gauged by GFAP mRNA. This was associated with reduced expression of APP695 KPI- isoform, the major neuronal isoform. These changes were not observed after PTZ where there was no neuronal loss and no glial reaction. The KA induced changes in APP were prevented by pretreatment with the non-competitive NMDA receptor antagonist dizocilpine and the barbiturate pentobarbitone, but not with the kappa-opioid receptor agonist enadoline. These findings were related to the suppression of seizures and the survival of neurons. In conclusion, excitotoxic stimulation leading to neuronal death was associated with increased expression of APP KPI+ mRNA and decreased APP KPI- mRNA, a finding which may relate to the plasticity of the central nervous system.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Benzofurans; Brain; Dizocilpine Maleate; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Humans; Kainic Acid; Male; Neuroprotective Agents; Neurotoxins; Organ Specificity; Pentobarbital; Pentylenetetrazole; Pyrrolidines; Rats; Rats, Wistar; RNA, Messenger; Transcription, Genetic; Trypsin Inhibitor, Kunitz Soybean

Previous pharmacological studies have indicated the possible existence of functional interactions between mu-, delta- and kappa-opioid receptors in the CNS. We have investigated this issue using a genetic approach. Here we describe in vitro and in vivo functional activity of delta- and kappa-opioid receptors in mice lacking the mu-opioid receptor (MOR). Measurements of agonist-induced [35S]GTPgammaS binding and adenylyl cyclase inhibition showed that functional coupling of delta- and kappa-receptors to G-proteins is preserved in the brain of mutant mice. In the mouse vas deferens bioassay, deltorphin II and cyclic[D-penicillamine2, D-penicillamine5] enkephalin exhibited similar potency to inhibit smooth muscle contraction in both wild-type and MOR -/- mice. delta-Analgesia induced by deltorphin II was slightly diminished in mutant mice, when the tail flick test was used. Deltorphin II strongly reduced the respiratory frequency in wild-type mice but not in MOR -/- mice. Analgesic and respiratory responses produced by the selective kappa-agonist U-50,488H were unchanged in MOR-deficient mice. In conclusion, the preservation of delta- and kappa-receptor signaling properties in mice lacking mu-receptors provides no evidence for opioid receptor cross-talk at the cellular level. Intact antinociceptive and respiratory responses to the kappa-agonist further suggest that the kappa-receptor mainly acts independently from the mu-receptor in vivo. Reduced delta-analgesia and the absence of delta-respiratory depression in MOR-deficient mice together indicate that functional interactions may take place between mu-receptors and central delta-receptors in specific neuronal pathways.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Anti-Arrhythmia Agents; Benzofurans; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Female; GTP-Binding Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neurons; Oligopeptides; Pain Measurement; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Respiration; Signal Transduction; Vas Deferens

mu-, delta- and kappa-opioid receptors are widely expressed in the central nervous system where they mediate the strong analgesic and mood-altering actions of opioids, and modulate numerous endogenous functions. To investigate the contribution of the kappa-opioid receptor (KOR) to opioid function in vivo, we have generated KOR-deficient mice by gene targeting. We show that absence of KOR does not modify expression of the other components of the opioid system, and behavioural tests indicate that spontaneous activity is not altered in mutant mice. The analysis of responses to various nociceptive stimuli suggests that the KOR gene product is implicated in the perception of visceral chemical pain. We further demonstrate that KOR is critical to mediate the hypolocomotor, analgesic and aversive actions of the prototypic kappa-agonist U-50,488H. Finally, our results indicate that this receptor does not contribute to morphine analgesia and reward, but participates in the expression of morphine abstinence. Together, our data demonstrate that the KOR-encoded receptor plays a modulatory role in specific aspects of opioid function.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Abdominal Pain; Analgesics, Opioid; Animals; Benzofurans; Humans; Mice; Mice, Knockout; Morphine; Nociceptors; Pyrrolidines; Receptors, Opioid, kappa

Fedotozine is a kappa opioid receptor agonist having antinociceptive properties but devoid of diuretic effects. The aim of the study was to evaluate the discriminative stimulus effects of fedotozine at doses previously reported to produce maximal effects in in vivo assays measuring kappa-mediated analgesia. By using a two-lever drug discrimination task, two groups of rats were trained to discriminate either a 3 mg/kg i.p. dose of the kappa opioid agonist, U50,488, or a 5 mg/kg i.p. dose of the mu opioid agonist, morphine, from saline. Once trained, rats were used to conduct tests of stimulus generalization with morphine, U50,488 and fedotozine along with another kappa agonist, CI-977, and another mu agonist, fentanyl. The stimulus effect of U50,488 was shared by CI-977 but not by morphine. Conversely, the stimulus effect of morphine was shared by fentanyl but not by U50,488. Fedotozine (1-10 mg/kg) failed to substitute to either U50,488 or morphine. These results indicate that, when administered at doses fully effective in producing antinociception, the interoceptive stimulus effects of fedotozine, if any, can be distinguished from those produced by U50,488 and morphine.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Benzofurans; Benzyl Compounds; Discrimination, Psychological; Dose-Response Relationship, Drug; Generalization, Stimulus; Male; Morphine; Propylamines; Pyrrolidines; Rats; Rats, Long-Evans; Receptors, Opioid, kappa

Peritoneal irritation in rats induced by i.p. administration of acetic acid produces abdominal contractions reflecting visceral pain, and gastrointestinal ileus characterized by inhibition of gastric emptying and small intestine transit. In this study, gastric emptying (GE) and intestinal transit, calculated by the geometric center (GC) method, were estimated using a test meal labeled with 51Cr-EDTA. Visceral pain was assessed by counting abdominal contractions. Acetic acid produced abdominal contractions (80.8 +/- 3.3) and inhibition of GE (-54%) and GC (-63%) during the test-period. The kappa-opioid receptor agonists, CI-977 (+/-)-U-50,488H, (+/-)-bremazocine, PD-117,302, (-)-cyclazocine, and U-69,583, reversed abdominal contractions and inhibitions of gastrointestinal transit in a dose-related manner. The mu-opioid receptor agonists and potent analgesics, morphine and fentanyl did not restore normal gastric emptying and intestinal transit. These data suggest that selective kappa-opioid receptor agonists might be used to treat abdominal pain associated with motility and transit impairment during postoperative ileus.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Acetic Acid; Analgesics; Animals; Benzofurans; Benzomorphans; Cyclazocine; Fentanyl; Gastric Emptying; Intestinal Pseudo-Obstruction; Male; Morphine; Naloxone; Naltrexone; Narcotic Antagonists; Pain; Peritoneum; Pyrroles; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Receptors, Opioid, mu; Thiophenes

Using in situ hybridization, we have shown that the kappa-opioid receptor agonist enadoline (CI-977) and the non-competitive NMDA receptor antagonist dizocilpine (MK-901) induced the immediate early gene c-fos in dorsal medial thalamic nuclei. Dizocilpine, and not enadoline, also induced c-fos in the posterior cingulate cortex and retrosplenial cortex. Enadoline's stimulation of c-fos mRNA was dose and time dependent and completely inhibited by pretreatment with naltrexone. Morphine did not stimulate c-fos in the thalamus. It is suggested that the stimulation of c-fos with enadoline represents a specific kappa-opioid receptor effect.

Topics: Analysis of Variance; Animals; Autoradiography; Benzofurans; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gene Expression Regulation; Genes, fos; Genes, Immediate-Early; In Situ Hybridization; Injections, Intraperitoneal; Male; Pyrrolidines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Receptors, Opioid, kappa; RNA, Messenger; Thalamic Nuclei

The present study characterized the electroencephalographic (EEG) effects of the neuroprotective kappa opioids enadoline and PD117302 in conscious, freely moving rats with the use of computer-assisted spectral analysis (CASA). Enadoline (25-100 microg/kg) or PD117302 (1.25-5.0 mg/kg) was administered intravenously to rats implanted with cortical EEG electrodes. Although both drugs produced an immediate, mild sedation, there were no signs of head-weaving or ataxia, and there was little visual evidence of opioid-like EEG slow-wave bursts or seizures. Both drugs produced only modest increases in total EEG power that were not dose dependent. In contrast, CASA revealed significant dose-dependent frequency shifts in relative power distributions, thereby identifying distinct kappa opioid alterations in awake EEG activity; EEG power decreased in the 0- to 4-Hz frequency band with concomitant increases in power measured in the 4- to 8-Hz frequency range. The kappa opioids produced a dose-dependent consolidation of the EEG waveform centered about a peak frequency of 5.0 Hz (for enadoline) or 4.8 Hz (for PD117302) and a significant shift in the mean EEG frequency from 6.6 Hz (predrug) to 6.2 Hz (postdrug). Further CASA revealed significant postdrug decreases in the edge frequency, mobility and complexity of the EEG. Both drugs produced moderate increases in the latency to slow-wave sleep (SWS). Overall, enadoline (ED50 = 18 microg/kg) was approximately 94 times more potent than PD117302 (ED50 = 1690 microg/kg) in producing the kappa EEG profile. Because the kappa-induced EEG changes were stereospecific for the (-)-enantiomers and inhibited by norbinaltorphimine (nor-BNI), the EEG "fingerprint" described in this study could be attributed to specific activation of brain kappa opioid receptors.

Topics: Animals; Benzofurans; Electroencephalography; Male; Narcotics; Neuroprotective Agents; Pyrroles; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Thiophenes

Previous results using an amphibian model showed that systemic and spinal administration of opioids selective for mu, delta and kappa-opioid receptors produce analgesia. It is not known whether non-mammalian vertebrates also contain supraspinal sites mediating opioid analgesia. Thus, opioid agonists selective for mu (morphine; fentanyl), delta (DADLE, [D-Ala2, D-Leu5]-enkephalin; DPDPE, [D-Pen2, D-Pen5]-enkephalin) and kappa (U50488, trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methanesulfonate; CI977, (5R)-(544alpha,744alpha,845beta)-N-methyl-N-[7-(1-p yrr olidinyl)-1-oxaspiro[4,5]dec-8yl]-4-benzofuranaceta mide++ + monohydrochloride) opioid receptors were tested for analgesia following i.c.v. administration in the Northern grass frog, Rana pipiens. Morphine, administered at 0.3, 1, 3 and 10 nmol/frog, produced a dose-dependent and long-lasting analgesic effect. Concurrent naltrexone (10 nmol) significantly blocked analgesia produced by i.c.v. morphine (10 nmol). ED50 values for the six opioids ranged from 2.0 for morphine to 63.9 nmol for U50488. The rank order of analgesic potency was morphine > DADLE > DPDPE > CI977 > fentanyl > U50488. These results show that supraspinal sites mediate opioid analgesia in amphibians and suggest that mechanisms of supraspinal opioid analgesia may be common to all vertebrates.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Opioid; Animals; Benzofurans; Dose-Response Relationship, Drug; Enkephalin, D-Penicillamine (2,5)-; Enkephalin, Leucine-2-Alanine; Enkephalins; Female; Fentanyl; Injections, Intraventricular; Male; Morphine; Naltrexone; Narcotics; Pyrrolidines; Rana pipiens; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu

The discriminative stimulus effects of enadoline were characterized in pigeons responding under a fixed-ratio 20 schedule of food presentation and discriminating between intramuscular injections of the kappa opioid agonist enadoline and saline. Cumulative doses of enadoline dose-dependently increased drug-key responding with the training dose of enadoline (0.178 mg/kg) producing > or = 90% drug key responding (% DR). In time course studies, doses of enadoline larger than 0.32 mg/kg produced > or = 90% DR for more than 40 min. Naltrexone antagonized both the discriminative stimulus and the rate-decreasing effects of enadoline (pA2 = 6.79 and 6.73, respectively); in some pigeons, naltrexone produced an unsurmountable antagonism of the enadoline discriminative stimulus. Substitution tests using the kappa agonists U-50,488, spiradoline, U-69,593 and ethylketocyclazocine resulted in > or = 90% DR in most, but not all, pigeons; at larger doses, all compounds markedly decreased response rates. Up to rate-decreasing doses, nalorphine, dynorphin A(1-13) amide (DYN), nalbuphine, butorphanol, morphine and ketamine failed to occasion > or = 90% DR; nalbuphine, nalorphine, butorphanol, but not DYN, antagonized the discriminative stimulus and the rate-decreasing effects of enadoline. This study established stimulus control with enadoline in pigeons and results from substitution studies in these pigeons support the view that the enadoline discriminative stimulus is mediated by kappa opioid receptors; these results further demonstrate that nalbuphine and butorphanol have kappa antagonist actions in pigeons. The negative results obtained with DYN are in contrast to previous demonstrations of kappa agonist effects for DYN and might provide support for the hypothesized importance of nonopioid systems in the effects of this peptide.

Topics: Animals; Benzofurans; Butorphanol; Columbidae; Discrimination Learning; Dose-Response Relationship, Drug; Dynorphins; Nalbuphine; Naltrexone; Pyrrolidines; Receptors, Opioid, kappa

In this study, the effect of intracerebroventricular (icv) administration of (5R)-(5 alpha, 7 alpha, 8 beta)-N-methyl-N-[7-(1-pyrrolindinyl)-1- oxaspiro[4,5]dec-8-yl]-4-benzofurnacetamide monohydrochloride (Cl-977) on pain behaviors and on spinal cord fos-like immunoreactivity (FLI) evoked by unilateral formalin injection into the hindpaw of rats was examined. Intracerebroventricular administration of Cl-977 (0.13-13.00 nmol) produced a dose-dependent inhibition of formalin-evoked pain behaviors, with significant inhibition after 1.30, 4.40 and 13.00 nmol. The estimated ED50 for icv Cl-977 inhibition of formalin-evoked behaviors was 0.95 nmol and the Emax was 53%. The inhibitory effect of 4.40 nmol of icv Cl-977 on formalin-evoked behaviors was prevented by either pretreatment with the kappa selective antagonist nor-binaltorphimine (10 or 100 nmol) or coadministration of the opiate receptor antagonist, naloxone (30 nmol). The lowest dose of icv Cl-977 tested (0.13 nmol) produced a 50% reduction in FLI in the superficial laminae but did not inhibit the expression of FLI in any other regions of the spinal cord. The fos-inhibitory effect of low-dose icv Cl-977 in the superficial cord was reversed by coadministration of naloxone (30 nmol). Higher doses of icv Cl-977 that suppressed formalin-evoked behaviors did not inhibit the expression of FLI in any region of the spinal cord. Finally, neither the inhibitory effect of 4.40 nmol Cl-977 on formalin-evoked behaviors nor the formalin-evoked pattern of FLI expression in the spinal cord of rats treated with this dose of Cl-977 was affected by lesions of the dorsolateral funiculus. These results provide the first evidence that supraspinal kappa receptor-mediated antinociception is not dependent on the integrity of the dorsolateral funiculus and may be mediated exclusively at the supraspinal level, suggesting that there are multiple mechanisms through which opioids can evoke antinociceptive effects.

Topics: Analgesics, Opioid; Animals; Benzofurans; Dose-Response Relationship, Drug; Formaldehyde; Male; Naloxone; Proto-Oncogene Proteins c-fos; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Receptors, Opioid, mu; Spinal Cord

The effect of the kappa-opioid agonist enadoline (CI-977) upon the relationship between cerebral blood flow and glutamate release was simultaneously assessed (using microdialysis and hydrogen clearance techniques respectively) at the same anatomical locus in the cerebral cortex (suprasylvian gyrus) after permanent middle cerebral artery (MCA) occlusion in halothane-anaesthetised cats. During controlled graded ischaemia, pretreatment with enadoline (0.3 mg/kg i.v. followed by continuous infusion at 0.15 mg/kg/h), initiated 30 min prior to MCA occlusion, significantly attenuated the marked increases in extracellular glutamate, aspartate and GABA observed in the focal ischaemic penumbra. The present data are consistent with the hypothesis that the neuroprotective efficacy of enadoline in focal cerebral ischaemia is due to inhibition of glutamate release in the ischaemic penumbra.

Topics: Animals; Anti-Arrhythmia Agents; Benzofurans; Blood Glucose; Body Temperature; Brain Ischemia; Cats; Cerebrovascular Circulation; Female; gamma-Aminobutyric Acid; Glutamic Acid; Microdialysis; Pyrrolidines; Receptors, Opioid, kappa; Stereotaxic Techniques; Tyrosine

A series of kappa/mu receptor chimeras and a number of kappa receptors substituted in the second transmembrane segment (TM-II) were investigated using as radioligands, respectively, the kappa-selective agonist [3H]C1977 and the nonselective opioid antagonist [3H]diprenorphine (DIP). All of the receptor constructs bound [3H]DIP with similar and high affinity, whereas the apparent affinity of the nonpeptide agonist C1977, when estimated in competition binding with the antagonist [3H]DIP, was impaired between 42- and > 500-fold in the kappa/mu chimeras and between 64- and 153-fold in three of the kappa receptor mutants that had been substituted in the TM-II segment. However, homologous competition binding experiments, using [3H]C1977 as radioligand, showed that the high affinity binding of this nonpeptide agonist was in fact not impaired in four of the kappa/mu chimeras and in three TM-II substituted kappa receptors compared with the wild-type kappa receptor. In all cases in which mutations decreased the apparent affinity of C1977 without affecting its actual affinity, as determined in homologous assays using [3H]C1977, the calculated number of receptor sites (Bmax) was decreased. In three of the kappa/mu constructs, binding of [3H]C1977 was undetectable, indicating that in these chimeras the affinity of the nonpeptide agonist had actually been affected. Also, for the kappa-selective peptide agonist dynorphin A(1-8), the measured affinity for the receptor mutants was strongly dependent on whether it was determined using the antagonist [3H]DIP or the agonist [3H]C1977 in that < or = 800-fold higher Ki values were determined in competition with the antagonist. It is concluded that mutations in the kappa-opioid receptor can cause large discrepancies between the affinity determined for agonists in homologous versus heterologous competition binding assays and that this pattern, which is compatible with a partial uncoupling of receptors, is observed in surprisingly many types of receptor mutations.

Topics: Animals; Benzofurans; COS Cells; Diprenorphine; Dynorphins; Kinetics; Mutation; Narcotic Antagonists; Peptide Fragments; Pyrrolidines; Radioligand Assay; Receptors, Opioid, kappa; Receptors, Opioid, mu; Recombinant Fusion Proteins; Tritium

Topics: Animals; Anti-Arrhythmia Agents; Benzofurans; Blood Pressure; Electric Stimulation; Electrocardiography; Heart; Heart Rate; Heart Ventricles; Ion Channels; Male; Myocardium; Pyrroles; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Stereoisomerism; Thiophenes

Parkinson's disease is characterized by an increased excitatory amino acid transmission in the internal segment of the globus pallidus and the substantia nigra pars reticulata. The effects of the kappa receptor agonist enadoline (CI-977) on glutamate transmission were investigated in vitro. Enadoline reduced the K(+)-evoked release of glutamate from slices of substantia nigra in a concentration-dependent manner (maximum effect: 78% inhibition at 200 microM). This effect was blocked by the selective kappa receptor antagonist nor-binaltorphimine. The endogenous ligand for kappa receptors is thought to be dynorphin. Dynorphin released from terminals of striato-pallidal and striato-nigral pathways might thus act as an endogenous modulatory agent on glutamatergic transmission in the basal ganglia. In vivo experiments were carried out in rodent and primate models of Parkinson's disease to assess the potential of manipulating kappa receptors as a potential treatment for Parkinson's disease. Enadoline reduced reserpine-induced akinesia when injected in the entopeduncular nucleus of the rat. Similarly, injections of CI-977 in the internal segment of globus pallidus (GPi) of the MPTP-treated marmoset alleviated parkinsonian symptoms and allowed the animal to recover its locomotor activity. This suggest that reducing the overactive glutamatergic transmission in the output regions of the basal ganglia by activating kappa receptors might potentially form the basis of a novel anti-parkinsonian therapy.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Animals; Anti-Arrhythmia Agents; Basal Ganglia; Benzofurans; Callithrix; Female; Glutamic Acid; In Vitro Techniques; Male; Motor Activity; Naltrexone; Parkinson Disease, Secondary; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Reserpine; Synaptic Transmission

Earlier reports indicate that kappa-opioid agonists may be especially potent in the formalin test of tonic nociception, and that neonatal rat pups are more sensitive to mu-agonists, when compared to adults. We have assessed the potency of enadoline (CI-977), a novel and selective kappa-opioid agonist, in the formalin and tail-flick nociceptive tests in 3-day-old rat pups and compared their responses to adults in the same tests. In addition, the recent cloning of the kappa-opioid receptor has allowed us to make the first evaluation of the ontogeny of kappa-opioid receptor mRNA in an effort to elucidate a possible mechanism for differences in sensitivity to kappa-opioid agonists. Enadoline was found to be a potent antinociceptive agent in the formalin test; the neonates were eight times more sensitive than the adults. kappa-Opioid receptor mRNA, however, is present in whole brain at adult levels as early as postnatal day 3. Previous studies have shown kappa-opioid receptor levels, as measured by radioligand binding and receptor autoradiography, to be present at postnatal day 3 as well. Consequently, it is unlikely that gross differences in receptor number subserved the modest increase in sensitivity to enadoline observed in the neonates in the formalin test. Enadoline was less potent and less effective in the tail-flick test in the neonates. The adults were similarly insensitive to the antinociceptive effects of enadoline in the tail-flick test. Additional studies indicated that enadoline significantly increased locomotor activity, as assessed by the open-field test, in neonates, while decreasing activity in the adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Age Factors; Analgesics, Opioid; Animals; Animals, Newborn; Arousal; Benzofurans; Dose-Response Relationship, Drug; Gene Expression; Male; Nociceptors; Pain Threshold; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; RNA, Messenger

The effect of the kappa-opioid receptor agonist enadoline (CI977, (5R)-(5 alpha,7 alpha,8 beta)-N-methyl-N-[7-(1-pyrrilidinyl)-1-oxaspiro [4,5]dec-8-yl-4-benzofuranacetamide monohydrochloride), on the release of amino acids was studied in the hippocampus of freely moving rats. K+, 100 mM, or veratrine, 100 microM, were applied for 10 min via the dialysis probe, either alone (control groups) or together with CI977 (after a 10 min pretreatment with CI977 in the perfusion medium). To test the specificity of the response to CI977, nor-binaltorphimine, a selective kappa-opioid receptor antagonist, was delivered together with CI977 in two groups of animals. To test the effect of systemic injection, CI977 was given subcutaneously 30 min prior to either stimulus. K(+)-induced release of glutamate and aspartate was significantly reduced by CI977, 2.5 mM; release of gamma-aminobutyric acid (GABA) was reduced by 250 microM CI977 in the probe. The effect of CI977 on release of glutamate and aspartate, but not of GABA, was reversed by nor-binaltorphimine (45 microM). Systemic treatment with CI977, 1 or 10 mg/kg, did not reduce K(+)-induced release of glutamate. Veratrine-induced release of aspartate and glutamate was significantly inhibited by 25 microM and release of GABA by 250 microM CI977 in the probe, and this effect was not modified by nor-binaltorphimine (58 microM). Systemic injection of CI977 1 mg/kg significantly reduced veratrine-induced release of glutamate. These results indicate that CI977 regulates release of amino acids by two independent mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acids; Animals; Benzofurans; Chromatography, High Pressure Liquid; Hippocampus; Male; Potassium; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Veratrine

The agonist and antagonist effects of intravenously administered dynorphin A-(1-13) were characterized in the warm water (50 and 55 degrees C) tail withdrawal assay of antinociception in rhesus monkeys. The peptide dose-dependently elevated tail withdrawal latencies in 50 degrees C water, but was ineffective in 55 degrees C water. The antinociceptive effect of dynorphin was surmountably antagonized by quadazocine (0.1 mg/kg) and nor-binaltorphimine (3.2 mg/kg), but was not antagonized by clocinnamox (0.1 mg/kg); this pattern of antagonism is consistent with a kappa-opioid receptor mediated effect. Pretreatment with dynorphin A-(1-13) (0.032-3.2 mg/kg) antagonized the antinociceptive effects of U50,488 and U69,593 in 55 degrees C water, suggesting a low efficacy action of the peptide at the receptors activated by these kappa agonists. However, dynorphin A-(1-13) (3.2 mg/kg) did not antagonize other kappa agonists: bremazocine (0.018-0.056 mg/kg) and enadoline (0.0056-0.018 mg/kg). Taken together, these dynorphin A-(1-13) findings support the notion of functional kappa-opioid receptor subtypes, and it appears that dynorphin A-(1-13) has limited efficacy at one of these sites. Finally, dynorphin A-(1-13) (0.32 mg/kg) also antagonized the antinociceptive effects of the mu-agonist etonitazene (0.0018-0.01 mg/kg).

Topics: Analgesics; Analgesics, Opioid; Animals; Anti-Arrhythmia Agents; Benzimidazoles; Benzofurans; Dynorphins; Hot Temperature; Macaca mulatta; Narcotics; Nociceptors; Pain Measurement; Peptide Fragments; Pyrrolidines; Receptors, Opioid, kappa

Substantiating evidence has raised the possibility that sigma ligands may have therapeutic potential as neuroprotective agents in brain ischemia. It has been suggested that the neuroprotective capacity of sigma ligands is related primarily to their affinity for the NMDA receptor complex and not to any selective action at the sigma binding site. However, sigma specific ligands, devoid of significant affinity for the NMDA receptor, are also neuroprotective via an inhibition of the ischemic-induced presynaptic release of excitotoxic amino acids. In the present study, we have investigated the potential neuroprotective effect of a comprehensive series of sigma ligands, with either significant (sigma/PCP) or negligible (sigma) affinity for the PCP site of the NMDA receptor, in order to delineate a selective sigma site-dependent neuroprotective effect. For this aim, we have employed two different neuronal culture toxicity paradigms implicating either postsynaptic-mediated neurotoxicity, (brief exposure of cultures to a low concentration of NMDA or Kainate) or pre- and postsynaptic mechanisms (exposure to hypoxic/hypoglycemic conditions). Only sigma ligands with affinity for the NMDA receptor [(+) and (-) cyclazocine, (+) pentazocine, (+) SKF-10047, ifenprodil and haloperidol] were capable of attenuating NMDA-induced toxicity whereas the sigma [(+)BMY-14802, DTG, JO1784, JO1783, and (+)3-PPP] and kappa-opioid [CI-977, U-50488H] ligands, with very low affinity for the NMDA receptor, were inactive. The rank order of potency, based on the 50% protective concentration (PC50) value, of sigma/PCP ligands against NMDA-mediated neurotoxicity correlates with their affinity for the PCP site of the NMDA receptor, and not with their affinity for the sigma site. In addition sigma/PCP, sigma or kappa-opioid ligands failed to attenuate kainate-mediated neurotoxicity. On the other hand, sigma/PCP, sigma and kappa-opioid ligands were potent inhibitors of hypoxia/hypoglycemia-induced neurotoxicity, although their neuroprotective potency did not correlate with their affinity for either the sigma or PCP binding sites. In conclusion, the ability of sigma and kappa-opioid ligands to attenuate hypoxia/hypoglycemia, but not NMDA or kainate-induced toxicity, suggests that these drugs exert their neuroprotective role by a predominantly presynaptic mechanism possibly by inhibiting ischemic-mediated glutamate release.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anti-Arrhythmia Agents; Antihypertensive Agents; Benzofurans; Brain Ischemia; Cell Death; Cells, Cultured; Dizocilpine Maleate; Hypoxia; Kainic Acid; Ligands; N-Methylaspartate; Neurons; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Receptors, Phencyclidine; Receptors, sigma

The influence of the kappa-opioid receptor agonist, enadoline, on endogenous glutamate release was investigated in rat and marmoset striatal synaptosomes. Enadoline decreased 4-aminopyridine (2 mM)-stimulated glutamate release (rat: IC50 approximately 8.7 microM, marmoset: IC50 approximately 2.9 microM). The effect of enadoline was reversed by nor-binaltorphimine (5 microM). These data indicate that, in the striatum of the rat and marmoset, kappa-opioid receptor agonists can modulate glutamate release. These findings may have implications for the treatment of Parkinson's disease.

Topics: 4-Aminopyridine; Animals; Benzofurans; Callithrix; Corpus Striatum; Glutamic Acid; Male; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Synaptosomes

Microdialysis was utilized to evaluate the effects of selective kappa-opioid receptor agonists on dopamine levels in the dorsal caudate of conscious rats. Subcutaneous administration of equivalent antinociceptive doses of spiradoline--(+/-)-(5 alpha, 7 alpha, 8 beta)-3, 4-dichloro-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec-8-yl] benzeneacetamide--(U62066; 12 mg/kg), BRL 52656--(2S)-1-[(4- trifluoromethylphenyl)acetyl]-2-[(1-pyrrolidinyl)methyl]piperidine--(2 mg/kg) and enadoline--(-)-(5 beta, 7 beta, 8 alpha)-N-methyl-N-[7-(1- pyrrolidinyl)-1-oxaspiro[4,5]dec-8-yl]benzo[b]furan-4-acetamide-- (CI-977; 0.1 mg/kg) produced similar, statistically significant decreases in dorsal caudate dopamine levels; BRL 53001--(2S)-2- (dimethylaminomethyl)-1-[(5,6,7,8-tetrahydro-5-oxo-2-naphthyl)ace tyl] piperidine--(12 mg/kg) was, however, without effect. At a higher dose (36 mg/kgP, BRL 53001 also caused a significant reduction in dopamine levels. BRL 52974--4-(1-pyrrolidinylmethyl) 5-[(3,4-dichlorophenyl)acetyl]-4,5,6,7-tetrahydroimidazo[4,5-c] pyridine, a selective kappa-opioid receptor agonist with limited ability to cross the blood brain barrier or produce antinociceptive effects, had no effect on dopamine levels at 10 mg/kg s.c. Overall, these findings suggest that selective kappa-opioid receptor agonists decrease dopamine levels in the dorsal caudate of rats via a central locus of action. Furthermore, compared to other kappa-opioid receptor agonists, BRL 53001 appears to have a reduced propensity to decrease dopamine levels at equianalgesic doses.

Topics: Analgesics; Animals; Anti-Arrhythmia Agents; Benzofurans; Caudate Nucleus; Chromatography, High Pressure Liquid; Diuretics; Dopamine; Injections, Subcutaneous; Male; Microdialysis; Pyridines; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Structure-Activity Relationship

The effect of the neuroprotective kappa opioid agonist CI-977 on glutamate (GLU)-stimulated calcium signaling was studied in individual primary rat cortical neurons. Using laser scanning confocal microscopy and the fluorescent calcium probe fluo-3, both the sustained and biphasic intracellular calcium concentration [Ca2+]i changes induced by GLU (20-40 microM) were altered by CI-977 (25-100 nM), thereby shifting the neuronal population response from unbuffered to buffered patterns of [Ca2+]i flux. This effect was consistent with the previously demonstrated neuroprotective action of CI-977 against glutamate toxicity in vitro. The effect of CI-977 in altering GLU-induced [Ca2+]i signaling was attenuated by naloxone, consistent with a neuroprotective action of CI-977 at opioid receptors, presumably of the kappa subtype.

Topics: Animals; Benzofurans; Calcium; Excitatory Amino Acids; Glutamic Acid; Neurons; Neuroprotective Agents; Osmolar Concentration; Pyrrolidines; Rats; Receptors, Opioid, kappa; Signal Transduction

Nalmefene [17-N-cyclopropylmethyl-3,14-beta-dihydroxy-4,5-alpha-epoxy-6- methylenemorphinan hydrochloride (also NIH 10365)], a 6-methylene derivative of naltrexone, was compared to naltrexone for its behavioral effects in rhesus monkeys. Nalmefene had opioid antagonist actions under all conditions, having a potency similar to that of naltrexone. In morphine-treated monkeys, discriminating between 0.01 mg/kg of naltrexone and saline, nalmefene substituted completely for naltrexone at doses larger than 0.001 mg/kg. The onset of discriminative stimulus effects was similar for nalmefene and naltrexone. A dose of 0.032 mg/kg of either antagonist occasioned > or = 90% naltrexone-level responding beginning 6 to 8 min after s.c. administration; the effects of this dose of either antagonist persisted for more than 1 hr. Like the parent compound naltrexone, nalmefene also antagonized the discriminative stimulus effects of opioid agonists. Nalmefene prevented the discriminative stimulus effects of morphine in monkeys acutely deprived of morphine and antagonized the discriminative stimulus effects of nalbuphine in a separate group of monkeys discriminating between nalbuphine and saline. At the dose of naltrexone and nalmefene that produced an equivalent antagonism of morphine when the antagonist was administered 0.25 hr before morphine (0.01 mg/kg), the duration of antagonist action was < 4 hr and > 6 hr, respectively. Nalmefene also attenuated the antinociceptive effects of the mu agonist alfentanil and the kappa agonist CI-977 [5R-(5,7,8-beta)-N-methyl- N-[7-(1-pyrrolidinyl)1-oxaspiro[4,5]dec-8-yl]-4-benzofuranaceta mide], being 55 times more potent in attenuating the antinociceptive effects of alfentanil as compared to Cl-977.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alfentanil; Analgesics; Animals; Behavior, Animal; Benzofurans; Female; Macaca mulatta; Male; Molecular Structure; Nalbuphine; Naltrexone; Narcotic Antagonists; Pyrrolidines

D-Serine, a selective agonist for the strychnine-insensitive glycine allosteric site associated with the NMDA receptor-ion channel complex, was found to modulate differentially the antinociception produced by kappa and mu-opioid receptor agonists in the rat formalin test. D-Serine (100 micrograms, i.c.v.) attenuated the antinociception produced by the selective kappa-opioid agonist, enadoline (0.003-0.1 mg kg-1, s.c.) against the tonic, but not acute, phase of the formalin response. Conversely, D-serine potentiated the antinociception produced by morphine (0.3-10 mg kg-1, s.c.) against both the acute and tonic phases. These results demonstrate an important interaction between the opioid and NMDA/glycine systems in the control of nociceptive information possibly at different levels of the neuraxis.

Topics: Analgesia; Animals; Benzofurans; Male; Morphine; Pyrrolidines; Rats; Rats, Wistar; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Receptors, Opioid, kappa; Receptors, Opioid, mu; Serine

Effects of the kappa opioid agonists, spiradoline (U62,066), enadoline (CI-977) and U69,593, were examined alone and in combination with the opioid antagonists quadazocine and beta-funaltrexamine in squirrel monkeys that responded under a schedule of shock titration. When given alone, each of these agonists increased the intensity at which the monkeys maintained shock 50% of the time (median shock level, MSL). Lower doses of spiradoline, enadoline and U69,593 increased response rates in some monkeys and higher doses decreased response rates in all monkeys. When given in combination with the opioid antagonist quadazocine, the dose-effect curves of each agonist, both for MSL and response rates, were shifted to the right in a dose-related and parallel manner. The slopes for the regression lines of the Schild plots for each agonist-quadazocine interaction approximated unity and apparent pA2 values for quadazocine in combination with these agonists ranged between 6.68 and 6.81 for MSL and between 6.63 and 6.87 for response rate. The effects of these agonists were not changed by an 8.0 mg/kg dose of beta-funaltrexamine that markedly antagonized the effects of morphine. These results parallel those previously obtained with other kappa agonists, such as bremazocine and U50,488 and suggest that the antinociceptive effects of spiradoline, enadoline and U69,593 in the shock-titration procedure in squirrel monkeys relate to activity at non-mu, probably kappa, opioid receptors.

Topics: Analgesics; Animals; Azocines; Benzeneacetamides; Benzofurans; Dose-Response Relationship, Drug; Male; Morphine; Naltrexone; Narcotic Antagonists; Pyrrolidines; Receptors, Opioid, kappa; Saimiri

The effects of the kappa-opioid agonist CI-977 upon local cerebral glucose utilization have been examined in conscious, lightly restrained rats to gain insight into the potential adverse effects of this neuroprotective agent. Cerebral glucose utilization was assessed quantitatively in 45 anatomically discrete brain regions by means of [14C]2-deoxyglucose autoradiography. The i.v. administration of CI-977 (0.03-3 mg/kg) induced relatively homogeneous patterns of altered cerebral glucose utilization with moderate statistically significant reductions (approximately 25%) being observed in 29 brain regions, and a statistically significant increase (approximately 40%) in one brain region, the lateral habenular nucleus. Glucose use throughout the entire neocortex and inferior colliculus was particularly sensitive to reduction (approximately 35%) following CI-977 administration, although there was only a limited dose dependency to the response. Minimal alterations in glucose use were observed in 15 of the 45 brain regions, particularly in the lower brain stem (e.g. superior olives, cochlear nucleus and median raphe) and forebrain limbic regions (e.g. septal nucleus, nucleus accumbens and mediodorsal thalamus). These data demonstrate that CI-977 produces widespread, anatomically organized alterations in function-related glucose use which contrast those seen previously with the NMDA receptor antagonists, thereby suggesting that CI-977 may be intrinsically safer as an in vivo neuroprotective agent.

Topics: Animals; Auditory Cortex; Autoradiography; Behavior, Animal; Benzofurans; Brain; Deoxyglucose; Extrapyramidal Tracts; Glucose; Limbic System; Male; Myelin Sheath; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Somatosensory Cortex; Visual Cortex

The selective kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI) has been shown to modulate cannabinoid-induced antinociception by delta 9-tetrahydrocannabinol (delta 9-THC). However, it is not known whether nor-BNI blocks other pharmacological effects of delta 9-THC or if this is a specific action of nor-BNI. Studies were conducted in which pretreatment with nor-BNI (2, 10 and 20 micrograms i.t.) selectively blocked delta 9-THC-induced antinociception while not significantly affecting other commonly observed cannabinoid actions, which included hypothermia, hypoactivity and catalepsy. Chronic administration studies were performed to determine if cross tolerance could be established between delta 9-THC and the highly specific kappa opioid receptor agonists, U-50,488H and CI-977. The chronic delta 9-THC-treated groups were significantly tolerant, not only to i.t. delta 9-THC-induced antinociception in the tail-flick test, but also to i.t. U-50,488 and CI-977 compared with those treated chronically with vehicle. They were not cross tolerant to either DAMGO or DPDPE. Dose-response curves were generated for both delta 9-THC (i.t.) and CI-977 (i.t.) in mice tolerant to delta 9-THC and CI-977. Parallel shifts to the right of the delta 9-THC dose-response curves were observed in animals tolerant to delta 9-THC and also in animals tolerant to CI-977. Animals tolerant to CI-977 also demonstrated parallel shifts of the dose-response curves of both delta 9-THC and CI-977. This study demonstrated that cannabinoid actions can be distinguished from each other. The pharmacological separation of antinociception from the other cannabinoid-induced actions implies that it may have a mechanism distinct from other effects. In addition, this study indicates that delta 9-THC and the kappa opioid agonists may share a common mechanism of action in the production of antinociception and that a possible interaction exists between i.t. administered cannabinoid compounds and the kappa opioid receptor.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzofurans; Dronabinol; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Male; Mice; Mice, Inbred ICR; Naltrexone; Pyrrolidines; Receptors, Opioid, kappa

The present study examined the discriminative stimulus and response rate-decreasing effects of kappa opioids in pigeons trained to discriminate a 0.017 mg/kg dose of bremazocine from saline. Bremazocine, spiradoline, CI977, U69,593 and U50,488 substituted completely for the bremazocine stimulus in a dose-dependent and naloxone-reversible manner. Apparent pA2 values (range, 6.01-6.81) of naloxone against the discriminative stimulus effects of these kappa opioids were smaller than those reported previously in the pigeon for naloxone against the discriminative stimulus effects of various mu opioids. Bremazocine, CI977, spiradoline and U69,593 also decreased rate of responding in a dose-dependent and naloxone-reversible manner. The apparent pA2 values (range, 6.25-6.44) for naloxone against the rate-decreasing effects of bremazocine, CI977 and U69,593 were not different from the apparent pA2 values for naloxone against their discriminative stimulus effects. An apparent pA2 for naloxone against the rate-decreasing effects of spiradoline could not be determined due to the shallow slope of the Schild plot. Although the rate-decreasing effects of U50,488 were antagonized by naloxone, the degree of antagonism was small and not dose-dependent. These findings indicate that the discriminative stimulus and rate-decreasing effects of some kappa opioids are mediated by similar mechanisms and that a non-opioid mechanism may contribute to the rate-decreasing effects of spiradoline and U50,488.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzofurans; Columbidae; Discrimination Learning; Dose-Response Relationship, Drug; Female; Naloxone; Narcotics; Pyrrolidines; Receptors, Opioid, kappa

The ability of five agents (dizocilpine [MK-801], 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline [NBQX], enadoline [CI-977], L-nitroarginine methyl ester [L-NAME] and BW 1003c87) with well defined, distinct pharmacological profiles and with established anti-ischemic efficacy, to modify neuronal damage has been examined in a simple in vivo model of glutamate excitotoxicity. Cortical lesions were produced in physiologically-monitored halothane-anesthetised rats by reverse dialysis of glutamate. The volume of the lesion was quantified histologically by image analysis of approximately 20 sections taken at 200 microm intervals throughout the lesion. The AMPA and NMDA receptor antagonists (NBQX and MK-801) and the inhibitor of nitric oxide synthase (L-NAME) significantly reduced the lesion volume by a similar extent (by approximately 30% from vehicle). Two agents (the kappa opioid agonist, CI-977 and the sodium channel blocker, BW 1003c87) which putatively inhibit the release of endogenous glutamate presynaptically, had dissimilar effects on lesion size. CI-977 failed to alter the amount of damage produced by exogenous glutamate, whereas BW 1003c87 reduced the lesion size by approximately 50%. Using this model, the neuroprotective effects of anti-ischemic drugs can be explored in vivo, uncomplicated in contrast to experimental ischemia by reduced oxygen delivery, drug effects on tissue blood flow and compromised energy generation. In consequence, additional mechanistic insight into anti-ischemic drug action in vivo can be obtained.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Benzofurans; Blood Pressure; Brain Ischemia; Cerebral Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamates; Glutamic Acid; Male; Microdialysis; Neurons; Neurotoxins; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Pyrimidines; Pyrrolidines; Quinoxalines; Rats; Rats, Sprague-Dawley; Time Factors

1. The evidence for kappa-receptor heterogeneity is equivocal. We have now investigated this question by comparing the effects of five putatively selective kappa-agonists. The parameters examined were: the relative potencies in depressing hindlimb flexor muscle reflexes to noxious pinch stimuli in both spinalized and sham-spinalized rats; the reversibility of these effects by naloxone; and the effects on blood pressure. 2. Two types of drug effect was discriminated. One drug group, represented by U-50,488, U-69,593 and PD-117,302, had a potency ratio between sham and spinalized rats approximately 10 fold lower than the other group, which comprised GR103545 and CI-977. 3. Under sham-spinalized conditions, CI-977 and GR103545 at high doses caused only sub-maximal reductions of spinal reflexes. U-50,488 was still active when superimposed on these high doses of GR103545. 4. Naloxone reversed all effects, but different doses were required between compounds, with GR103545 taking some 20 times higher doses of naloxone to cause reversal than did U-50,488. 5. The effects on mean arterial pressure were opposite between groups. 6. The results imply that more than one type of naloxone-sensitive non-mu opioid receptor must be involved in mediating these complex actions of ligands that have been claimed to be selective for kappa-receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Anticonvulsants; Benzeneacetamides; Benzofurans; Blood Pressure; Decerebrate State; Male; Naloxone; Nociceptors; Piperazines; Pyrroles; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa; Reflex; Spinal Cord; Thiophenes

Administration of N-methyl-DL-aspartate (85 mg/ml) was given by infusion (0.14 ml/min) until a clonic seizure was elicited. In situ hybridization was used to assess regional levels of four immediate early gene messenger RNA levels (c-fos, c-jun, junB, and a nerve growth factor induced gene, NGFI-A). Messenger RNA levels were highest at 25 min following infusion of N-methyl-DL-aspartate. c-jun messenger RNA levels remained elevated for over 2 h; however, c-fos, junB and, NGFI-A messenger RNA levels had returned to control levels by this time. Expression was detected in the hippocampus, hypothalamus and piriform cortex. Pre-treatment (30 min prior to N-methyl-DL-aspartate) with the anticonvulsant drugs dizocilpine maleate (1 mg/kg) and HA 966 (200 micrograms, i.c.v.) resulted in significantly reduced immediate early gene messenger RNA levels in the hypothalamus and piriform cortex, and attenuated levels in the hippocampus. Pre-treatment with the anticonvulsant agent enadoline (3 mg/kg), given at an anticonvulsant dose, did not result in reduced immediate early gene messenger RNA levels. These results suggest that monitoring immediate early gene expression may lead to advances in the understanding of the mechanism of action of many pharmacological agents, such as the kappa-opioid agonist enadoline.

Topics: Animals; Anticonvulsants; Benzofurans; Brain; Brain Chemistry; Dizocilpine Maleate; Gene Expression; Genes, Immediate-Early; In Situ Hybridization; Male; Mice; Mice, Inbred Strains; N-Methylaspartate; Pyrrolidines; Pyrrolidinones; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Silver Staining

The neuroprotective efficacy of the kappa-opioid agonist enadoline (CI-977) was examined in two acute rat models of focal cerebral ischaemia [non-recovery (4 h) and recovery (24 h)]. In the non-recovery model, Sprague-Dawley rats were anaesthetized throughout the study period. Focal ischaemia was produced by the permanent occlusion of the left middle cerebral artery (MCA). The amount of early ischaemic damage was assessed in coronal sections at nine pre-determined stereotaxic planes. Enadoline at doses of 0.1, 0.3 and 1.0 mg/kg (n = 8), administered s.c. 30 min prior to ischaemia, produced dose-dependent amelioration of cortical damage. Importantly, enadoline had no significant effect on any of the physiological parameters monitored (blood pressure, blood gases, glucose, pH). In the recovery model the left MCA was permanently occluded under isoflurane anaesthesia. Animals were allowed to recover and were killed 24 h later. The amount of ischaemic brain damage and swelling was assessed histologically. In this model pretreatment with enadoline at either 0.1, 0.3, or 1.0 mg/kg s.c. was followed by continuous s.c. infusion at 0.017, 0.05 or 0.17 mg/kg/h respectively (n = 8-17). Enadoline produced dose-dependent reductions in the volumes of infarction and brain swelling; the greatest reductions were seen at 1.0 mg/kg plus 0.17 mg/kg/h in both infarction (reduced by 37.4% from controls) and swelling (reduced by 47.8%). Therefore the kappa-opioid agonist enadoline affords dose-dependent neuroprotection in both the non-recovery and recovery models of focal cerebral ischaemia in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzofurans; Brain; Brain Edema; Brain Ischemia; Cerebral Infarction; Dose-Response Relationship, Drug; Male; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa

The effects of the kappa-1 opioid agonist CI-977 upon the volume of ischemic brain damage (defined using quantitative neuropathology) and local cerebral blood flow (CBF) (defined using quantitative [14C]iodoantipyrine autoradiography) have been examined at 4 h and 30 min, respectively, after permanent middle cerebral artery (MCA) occlusion in halothane-anesthetised rats. Treatment with CI-977 (0.3 mg/kg, s.c.) 30 min before and 30 min after occlusion of the MCA reduced the volume of infarction in the cerebral hemisphere (reduced by 27% when compared to vehicle; P < 0.05) and cerebral cortex (reduced by 32%; P < 0.05), despite a marked and sustained hypotension, with only minimal effect on damage in the caudate nucleus. In the hemisphere contralateral to the occluded MCA, treatment with CI-977 (0.3 mg/kg, s.c.) 30 min prior to the induction of ischemia failed to demonstrate any significant effect on either the level of local CBF in any of the 25 regions examined or on the volume of low CBF determined by frequency distribution analysis. In the hemisphere ipsilateral to MCA occlusion, CI-977 failed to produce statistically significant alterations in either the level of local CBF in 23 of the 25 regions or on the volume of low CBF, but areas of hyperemia were observed in both the medial caudate nucleus and lateral thalamus (local CBF increased by 65% and 86%, respectively, when compared to vehicle).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antipyrine; Autoradiography; Benzofurans; Blood Pressure; Brain; Brain Ischemia; Cerebral Arteries; Cerebrovascular Circulation; Functional Laterality; Iodine Radioisotopes; Male; Organ Specificity; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Time Factors

Increases in mRNA levels for c-fos, c-jun, junB, hsp70 and NGFI-A were observed in the dentate gyrus of the hippocampus following 7 min ischaemia in the Mongolian gerbil. The response was rapid and transient (30 min to 4 hr) for NGFI-A, junB and c-fos mRNA. In contrast c-jun mRNA remained increased for several hours. Hsp70 increased in the dentate gyrus 1 hr after the insult, returned to control values at 4 hr and showed a secondary increase at 24 hr. At 24 hr increased hsp70 mRNA was observed in other regions of the CNS, i.e. CA1, CA2, CA3 and cortex. The non-competitive NMDA receptor antagonist, dizocilpine, attenuated the increases in IEG expression and was neuroprotective. In contrast the kappa opiate receptor agonist, enadoline, protected the CA1 neurones from degeneration but did not inhibit the increased levels of IEG mRNA. Increases in hsp70 mRNA were reduced to baseline by both enadoline and dizocilpine. These results suggest that inhibition of IEG expression is not a prerequisite for neuroprotection. However, hsp70 was predictive of neuronal protection and may be a useful assay in this and related models.

Topics: Animals; Autoradiography; Benzofurans; Brain Ischemia; Dizocilpine Maleate; DNA-Binding Proteins; Female; Gene Expression; Genes, Immediate-Early; Gerbillinae; Heat-Shock Proteins; Hippocampus; Pyrrolidines; Receptors, N-Methyl-D-Aspartate; Receptors, Opioid, kappa; RNA, Messenger; Transcription Factors

1. The S,S (-)-enantiomer PD 129290, a kappa agonist, and its corresponding inactive R,R (+)-enantiomer (PD 129289) were studied in rat isolated hearts and in intact rats for cardiovascular and antiarrhythmic actions. The electrophysiological actions of PD 129290 were also studied in rat isolated cardiac myocytes using voltage clamp. 2. Ventricular pressure, heart rate and ECG were studied in isolated hearts while blood pressure, heart rate and ECG were studied in pentobarbitone-anaesthetized rats. In the latter, responses to electrical stimulation and coronary occlusion were also investigated. 3. In isolated hearts both enantiomers, over the concentration range 2-16 microM, dose-dependently reduced systolic ventricular pressure and heart rate while prolonging the P-R and QRS intervals of the ECG. 4. At doses of 1-32 mumol kg-1 both enantiomers reduced blood pressure and heart rate in anaesthetized rats. In addition, both enantiomers increased the size of the RSh and increased P-R, QRS, and Q-T intervals of the ECG. The thresholds for premature beats and ventricular fibrillation were dose-dependently increased by PD 129289. At lower doses PD 129290 decreased thresholds. These decreases were blocked by naloxone to reveal underlying increases similar to those seen with PD 129289. Both enantiomers increased refractory periods. 5. Naloxone (8 mumol kg-1) did not alter any of the actions of PD 129290, except to abolish the initial decreases in thresholds in intact rats seen with lower doses of PD 129290. 6. Both enantiomers (2 and 8 mumol kg-1) equally reduced arrhythmias in anaesthetized rats subject to occlusion of a coronary artery. 7. In rat isolated cardiac myocytes 20 microM PD 129290, in the presence and absence of naloxone decreased the amplitude of the transient sodium current by about 50% without affecting the voltage dependence of activation or inactivation of this current.8. The antiarrhythmic actions of both enantiomers appear to primarily result from their Class I(sodium channel blockade) properties which are independent of kappa agonism.

Topics: Animals; Anti-Arrhythmia Agents; Benzofurans; Blood Pressure; Electric Stimulation; Electrocardiography; Heart; Heart Rate; In Vitro Techniques; Male; Narcotics; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Stereoisomerism

Mongolian gerbils were subjected to transient forebrain ischaemia by occluding both common carotid arteries for 7 min. Subcutaneous administration of either the kappa-opioid receptor agonist enadoline (CI-977; 1 mg kg-1), or the non-competitive NMDA receptor antagonist dizocilpine (MK-801; 3 mg kg-1), at induction of ischaemia prevented neurodegeneration of CA1-CA2 pyramidal neurones in the dorsal hippocampus. It was shown by continuously monitoring intrahippocampal temperature that brain temperature drops by approximately 4 degrees C during ischaemia, when rectal temperature is maintained normothermic. Enadoline at no time point tested affected brain temperature, whereas dizocilpine statistically lowered brain temperature following ischaemia. These findings suggest that enadoline affords neuroprotection in the absence of any hypothermic episode, whilst in the case of dizocilpine, the small transient hypothermia observed following ischaemia may act synergistically or additively with the drug to yield neuroprotection.

Topics: Animals; Benzofurans; Body Temperature; Brain; Dizocilpine Maleate; Female; Gerbillinae; Ischemic Attack, Transient; Models, Biological; Pyrrolidines

The effects of the kappa-1 opioid receptor agonist (5R)-(5 alpha,7 alpha,8 beta)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4,5]dec-8-yl]-4- benzofuranacetamide monohydrochloride (CI-977) upon ischemic brain damage have been examined in 15 halothane-anesthetized cats. Focal cerebral ischemia was produced by permanent occlusion of one middle cerebral artery (MCA), and the animals killed 6 h later. The amount of early ischemic brain damage was assessed in coronal sections at 16 predetermined stereotactic planes. Pretreatment with CI-977 (0.3 mg/kg i.v. followed by continuous infusion at 0.15 mg/kg/h until death), initiated 15 min prior to MCA occlusion, significantly reduced the volume of ischemic brain damage (from 2345 +/- 675 mm3 of the cerebral hemisphere in vehicle-treated cats to 1569 +/- 370 mm3 in CI-977-treated cats; P < 0.01). These data indicate that the kappa-1 opioid agonist CI-977 is neuroprotective in a model of focal cerebral ischemia in a gyrencephalic species where key systemic variables have been assessed throughout the entire post-ischemic period.

Topics: Animals; Benzofurans; Blood Glucose; Blood Pressure; Body Temperature; Brain; Cats; Cerebral Arteries; Hematocrit; Histocytochemistry; Ischemic Attack, Transient; Pyrrolidines; Receptors, Opioid, kappa

Intracellular recordings were made from neurons in a rat locus coeruleus slice preparation in vitro. A postsynaptic potential was evoked by electrical stimulation of afferents to the neurons. CI-977 ([5R-(5a,7a,8b)]-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec -8-yl[-4-benzofuranacetamide monohydrochloride) caused a depression of the evoked postsynaptic potential on locus coeruleus neurons. This action was reversed on washout. Bremazocine had a similar action on less than 50% of locus coeruleus neurons. Concentrations of CI-977 which depressed the postsynaptic potential did not affect either passive membrane conductance or a voltage-sensitive potassium current resembling IA. The depression of the excitatory postsynaptic potential caused by CI-977 remained in the presence of either 30 microM bicuculline and picrotoxin or when potassium acetate-filled recording electrodes were used. Using potassium chloride-filled recording electrodes and in the presence of 30 microM 6-cyano-2,3-dihydro-7-nitroquinoxaline-2,3-dione and either 30 microM DL-2-amino-5-phosphonovaleric acid or 500 microM kynurenic acid, CI-977 had no effect on the postsynaptic potential. The effects of CI-977 were reversed by 30-100 nM naloxone and 1-10 nM norbinaltorphimine but not by 1-10 nM naloxone. The hyperpolarizing response to the mu-opioid receptor-selective agonist D-Ala2,Nme Phe4,Gly-ol5 (DAGOL) was blocked by 1-10 nM naloxone but not by 1-100 nM norbinaltorphimine. The hyperpolarizing response to DAGOL was not affected by high doses of CI-977.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acids; Analgesics; Animals; Benzofurans; Benzomorphans; Bicuculline; Depression, Chemical; Electric Stimulation; Electrophysiology; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; In Vitro Techniques; Ligands; Locus Coeruleus; Membrane Potentials; Naloxone; Naltrexone; Picrotoxin; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Synapses

CI-977 is a selective, nonpeptide kappa opioid agonist. In rhesus monkeys, CI-977 is a potent antinociceptive agent against thermal stimuli after i.m. administration. Increasing the intensity of the nociceptive stimulus can reduce the analgesic activity of CI-977. Antinociceptive activity also was seen when PD 126212, containing CI-977 as the (-)-enantiomer, was administered sublingually. Naloxone antagonized the antinociceptive action of CI-977, demonstrating opiate receptor involvement in this activity. Monkeys treated with CI-977 also showed sedation at doses close to those required to produce antinociception. As with morphine, the sedative properties of CI-977 were associated with impaired cognitive performance. Aged monkeys appeared more sensitive than young monkeys to the performance-impairing effect of CI-977. Tolerance developed to the antinociceptive and response-suppressing effects. CI-977 was approximately 1000 times more potent than morphine as an analgesic when tested against a moderate (50 degrees C) thermal stimulus but less effective than morphine against a strong (55 degrees C) thermal stimulus.

Topics: Animals; Benzofurans; Cognition; Dose-Response Relationship, Drug; Drug Synergism; Female; Injections, Intramuscular; Macaca mulatta; Male; Morphine; Naloxone; Pain; Pyrrolidines; Receptors, Opioid

The effect of a novel, highly potent and selective kappa-opioid receptor agonist CI-977 upon ischaemic brain damage and brain swelling has been examined in a rat model of focal cerebral ischaemia. Focal ischaemia was produced by the permanent occlusion of the left middle cerebral artery (MCA) during a brief period of halothane anaesthesia. The animals were sacrificed 24 h after MCA occlusion and the amount of ischaemic brain damage and swelling was assessed in coronal sections at 8 predetermined stereotactic planes. Treatment with CI-977 (0.03, 0.3 or 3 mg/kg), initiated 30 min prior to MCA occlusion (and at multiple times thereafter) produced dose-dependent reductions in the volumes of infarction and of brain swelling, with the most marked reductions being noted with CI-977 (0.3 mg/kg) in both infarction (reduced by 38% from controls; P less than 0.02) and swelling (reduced by 31%; P less than 0.002). There was an excellent correlation between the volume of brain swelling and ischaemic damage which was similar with saline-treated and CI-977-treated animals (overall correlation coefficient r = 0.896). These results indicate that CI-977 is effective in reducing infarction in a model of focal cerebral ischaemia, and that the reduction in brain swelling occurs in parallel with the reduction in ischaemic damage.

Topics: Animals; Benzofurans; Brain Edema; Cerebral Infarction; Disease Models, Animal; Ischemic Attack, Transient; Male; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa

Intracellular recordings from dorsal raphé neurones in slices from rat brains were used to study the actions of kappa-opioid receptor agonists on an excitatory postsynaptic potential (epsp) evoked by local electrical stimulation of afferent terminals. The epsp was observed on all 5-HT-sensitive neurones and was blocked by 1 microM TTX. The epsp was reduced in a dose-dependent manner by the specific kappa-opioid receptor agonist [5R-(5 alpha,7 alpha,8 beta)]-N-methyl-N-[7-(1-pyrrolidinyl)-1- oxaspiro[4.5]dec-8-yl]-4-benzofuranacetamide monohydrochloride (CI-977) (1-100 nM). The effects of CI-977 were blocked by the specific kappa-opioid receptor antagonist norbinaltorphimine (NorBNI) (0.1-1 microM). In the presence of the GABAA receptor antagonists picrotoxin and bicuculline (30 microM), CI-977 still had its depressant action on the epsp. Application of the excitatory amino acid receptor antagonists either kynurenic acid (0.5-1 mM) or 6-cyano-2,3-dihydro-7-nitro-quinoxaline-2,3-dione (CNQX) (30 microM) and DL-2-amino-5-phosphonovaleric acid (APV) reduced both the peak and area of the epsp suggesting that the main component of the epsp evoked by electrical stimulation was largely due to release of excitatory amino acids from afferent terminals. Using potassium chloride-filled recording electrodes an epsp which was only partially occluded by kynurenic acid or CNQX and APV was seen on some neurones, this residual epsp was insensitive to CI-977 but was blocked by 30 microM picrotoxin and bicuculline. The specific mu-opioid receptor agonist, DAGOL, had no consistent effect on the fast epsp. Longer duration electrical stimuli produced a slow inhibitory postsynaptic potential (ipsp) and a long duration increase in firing. CI-977 did not affect either the slow 5-HT-mediated ipsp which was blocked by spiperone or the slow noradrenaline-mediated increase in firing which was sensitive to prazosin. CI-977 did not change the depolarizing response to brief applications of either glutamic acid or N-methyl-D-aspartic acid (NMDA). CI-977, NorBNI, naloxone, DAGOL, picrotoxin, bicuculline and kynurenic acid had no consistent effects on the resting postsynaptic membrane potential or conductance. Under voltage-clamp conditions CI-977 had no effect on a membrane current resembling IA. These results suggest that kappa-opioid receptors are present on the terminals of afferents which release excitatory amino acids onto the 5-HT-sensitive neurones in the raphé.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Afferent Pathways; Animals; Benzofurans; Bicuculline; Bombesin; Cholecystokinin; Electric Stimulation; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Evoked Potentials; Glutamates; Glutamic Acid; In Vitro Techniques; Kynurenic Acid; N-Methylaspartate; Naloxone; Naltrexone; Neurons; Picrotoxin; Prazosin; Pyrrolidines; Quinoxalines; Raphe Nuclei; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Serotonin; Synapses; Tetrodotoxin

The selective kappa-opioid receptor agonist CI-977, stereoselectively antagonised clonic seizures induced by slow i.v. infusion of N-methyl-DL-aspartate in the mouse. It was found to be more efficacious and 10-fold more potent than the competitive N-methyl-D-aspartic acid receptor antagonist CPP (3-(+/-)-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid). The anticonvulsant action of CI-977 was antagonised by norbinaltorphimine indicating a specific interaction with the kappa-receptor. The effect of CI-977 but not that of CPP was also antagonised by the glycine/NMDA receptor agonist D-serine. These results provide evidence for a possible interaction between the kappa-receptor and the glycine/NMDA receptor.

Topics: Animals; Anticonvulsants; Benzofurans; Dizocilpine Maleate; In Vitro Techniques; Mice; Mice, Inbred Strains; Naltrexone; Piperazines; Pyrrolidines; Radioligand Assay; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Opioid; Receptors, Opioid, kappa; Seizures; Stereoisomerism

1. CI-977 is a new, nonpeptide kappa-opioid compound that has been synthesized and its pharmacological properties determined in a series of in vitro and in vivo rodent models. 2. In a radioligand binding studies, with guinea-pig forebrain homogenates, CI-977 bound with high affinity to [3H]-U69593-labelled kappa-sites (Ki = 0.11 nM) but with low affinity to [3H]-[D-Ala2, MePhe4, Gly-ol5] enkephalin (DAMGO) labelled mu-sites (Ki = 99 nM) and [3H]-[D-Pen2.5]enkephalin (DPDPE) labelled delta-sites (Ki = 1.04 microM). CI-977 also bound with negligible affinity to [3H]-(+)-3-(1-propyl-3-piperi-dinyl)phenol (3-PPP) labelled sigma-sites (Ki = 1.9 microM) and [3H]-1-(1-[2-thienyl]cyclohexyl)piperidine (TCP) labelled PCP sites (Ki greater than 10 microM). 3. CI-977 produced a potent inhibition of the electrically-evoked contractions of the guinea-pig ileum and rabbit vas deferens with IC50 values of 0.087 nM and 3.3 nM, respectively. The pKB values for the opioid antagonists naloxone (7.6) and norbinaltorphimine (10.5) supported the kappa nature of the CI-977-mediated effects in the smooth muscle assays. 4. CI-977 was a potent antinociceptive agent against a mechanical noxious stimulus in rats following intravenous, intramuscular, subcutaneous and oral administration. CI-977 was also effective against mechanical and chemical noxious stimuli in the mouse but ineffective against a thermal stimulus. The antinociceptive effects produced by CI-977 were completely reversed by naloxone (1 mg kg-1, s.c.). 5. At doses close to those required to produce antinociception, CI-977 also caused a naloxone-reversible diuresis and inhibition of locomotor activity.6. The in vitro and in vivo pharmacological profile of CI-977 demonstrates that it is a potent and selective agonist at the Kappa-opioid receptor.

Topics: Analgesics; Animals; Benzofurans; Binding, Competitive; Brain; Diuretics; Dose-Response Relationship, Drug; Guinea Pigs; Ileum; In Vitro Techniques; Ligands; Male; Mice; Motor Activity; Muscle, Smooth; Pyrrolidines; Rabbits; Radioligand Assay; Rats; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Vas Deferens