u-50488 and bremazocine

Evidence from studies which utilise either opiate receptor agonists and antagonists strongly indicate a role for endorphinergic mechanisms in the control of feeding responses. Two means by which these compounds may exert an effect on feeding can be singled-out. Firstly, emerging evidence suggests that the process of achieving satiety (terminating a meal, or choice of a commodity) may be accelerated following treatments with opiate receptor antagonists. Secondly, the preference for highly palatable solutions (sweet solutions have received most attention) in two-bottle tests is blocked after injection of opiate receptor antagonists. This finding has been interpreted in terms of the abolition of the reward or incentive quality associated with the particularly attractive flavour. These two mechanisms of action may represent two aspects of a single, fundamental process. Following an introduction to rat urination model of in vivo kappa agonist activity, the consistent effect of several kappa agonists (including the highly selective U-50,488H) to stimulate food consumption is described. Recognising that members of the dynorphin group of endogenous opioid peptides are kappa receptor ligands, some with a high degree of selectivity, and the evidence the dynorphins and neo-endorphins produce hyperphagia in rats is particularly interesting. Such lines of evidence lead to the hypothesis that peptides of the dynorphin group may act endogenously to promote the expression of normal feeding behaviour.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzodiazepines; Benzomorphans; Butorphanol; Choice Behavior; Cyclazocine; Diuresis; Drinking; Dynorphins; Eating; Endorphins; Ethylketocyclazocine; Humans; Morphine; Narcotic Antagonists; Phenazocine; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Satiety Response

Kappa opioid receptor (KOR) agonists such as U-50488H and bremazocine are analgesics and diuretics. In monkeys, the selective KOR antagonist, nor-binaltorphimine (nor-BNI), produces a long-lasting antagonism of the antinociceptive effects of U-50488H but not those of bremazocine, suggesting that KOR-mediated antinociception may occur through two distinct KORs. The aim of this study was to characterize the antagonist effect of nor-BNI against the diuretic effects of U-50488H and bremazocine in monkeys. Urine outputs were collected over 3 h subsequent to i.m. administration of KOR agonists. Both U-50488H (0.032-1 mg/kg) and bremazocine (0.00032-0.01 mg/kg) dose-dependently increased urine output and the diuretic effect reached a plateau at higher doses. The maximum effect of either U-50488H or bremazocine was approximately 15 ml/kg/3 h of urine. Pretreatment with intracisternal nor-BNI 0.32 mg significantly blocked both U-50488H (0.18 mg/kg)- and bremazocine (0.0032 mg/kg)-induced diuresis for 20 weeks. However, the same dose of nor-BNI 0.32 mg given subcutaneously was not effective. These results demonstrate that central KOR mediate KOR agonist-induced diuresis in monkeys. More important, this study provides functional evidence for a homogenous population of KOR underlying KOR-mediated diuresis and illustrates a unique pharmacological profile of nor-BNI-induced ultra-long KOR antagonism in vivo.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Diuresis; Female; Injections, Intraventricular; Macaca mulatta; Male; Naltrexone; Narcotic Antagonists; Receptors, Opioid, kappa

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

Mesolimbic dopaminergic neurotransmission plays a critical role in the locomotor effects of psychostimulant drugs, but a general involvement in the induction of long-term psychostimulant sensitization is questionable. By influencing dopaminergic neurotransmission, opioid drugs can alter the behavioral effects of psychostimulants.. The effects of the kappa-opioid receptor agonists bremazocine, U69593, and U50488H on the locomotor stimulant and the long-term sensitizing effects of amphetamine and cocaine were investigated in rats. Unlike U69593 and U50488H, bremazocine is also an antagonist at mu- and delta-opioid receptors, as well as an agonist at a subtype of delta-opioid receptors inhibiting dopamine D1 receptor-stimulated adenylate cyclase.. Bremazocine, U69593, and U50488H were administered prior to amphetamine and cocaine, and locomotor activity was measured. In separate studies, the opioids were co-administered with amphetamine and cocaine for 5 days, and locomotor sensitization was assessed 3 weeks post-treatment.. Bremazocine and U69593 attenuated the psychomotor stimulant effects of amphetamine and cocaine. U50488H attenuated the locomotor effect of cocaine and biphasically affected amphetamine-induced locomotion, i.e., suppression followed by stimulation. Bremazocine prevented the development of amphetamine-induced but not cocaine-induced long-term sensitization. Neither U69593 nor U50448H affected the induction of long-term amphetamine or cocaine sensitization.. In agreement with previous studies, the present data suggest that differential mechanisms underlie the acute stimulant versus the long-term sensitizing effects of psychostimulants, and the induction of long-term sensitization by amphetamine versus cocaine. Stimulation of kappa-opioid receptors does not seem to block the induction of long-term psychostimulant sensitization. Thus, bremazocine is likely to block the induction of amphetamine sensitization through a non-kappa-opioid receptor mechanism. We suggest that this effect of bremazocine is the result of its unique agonist action at a subtype of delta-opioid receptors, thereby acting as a functional dopamine D1 receptor antagonist. This would be consistent with the literature showing that the induction of long-term amphetamine sensitization depends on the activation of dopamine D1 receptors. In addition, the present data are in keeping with studies showing that dopamine neurotransmission is not critical for the induction of long-term cocaine sensitization.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Amphetamine; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Central Nervous System Stimulants; Cocaine; Male; Motor Activity; Psychomotor Agitation; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa

The kappa-opioid agonists U50488H, bremazocine, and BRL52537, and the mu-opioid agonist morphine were compared in their ability to modify spontaneous motor activity in male NMRI mice. Higher, analgesic doses of the kappa-agonists reduced rearing, motility, and locomotion in nonhabituated mice. These effects, as well as the analgesic action of U50488H, were blocked by the selective kappa-opioid antagonists nor-binaltorphimine and DIPPA. In contrast, lower, subanalgesic doses (1.25 and 2.5 mg/kg for U50488H; 0.15 and 0.075 mg/kg for bremazocine, and 0.1 mg/kg for BRL52537) time dependently increased motor activity. The stimulatory effects of U50488H and bremazocine were not observed in habituated animals and were reduced by dopamine depletion. Surprisingly, the stimulatory effects of U50488H and bremazocine were not blocked by nor-binaltorphimine and DIPPA but they were completely eliminated by naloxone (0.1 mg/kg). The effects of morphine were dose-dependent; an initial limited suppression was followed by increased motility and locomotion (but not rearing) with a peak effect at 20 mg/kg both in habituated and nonhabituated mice. The selective mu-opioid antagonist beta-funaltrexamine blocked morphine-induced motor stimulation and analgesia but failed to affect the analgesic and motor stimulatory effects of U50488H. The results indicate that kappa-opioid agonists interact with different functional subtypes of opioid receptors. A stimulatory, naloxone-sensitive but nor-binaltorphimine- and DIPPA-insensitive subtype of opioid receptor appears to operate only when the dopamine system is tonically active in nonhabituated animals. At higher doses, kappa-agonists produce analgesia and motor suppression, effects mediated by a "classic" (inhibitory) kappa-opioid receptor.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Acetamides; Animals; Benzomorphans; Dose-Response Relationship, Drug; Isothiocyanates; Male; Mice; Morphine; Motor Activity; Naloxone; Naltrexone; Receptors, Opioid, kappa; Time Factors

The mechanism by which kappa-opioid receptor (kappaor) modulated apoptosis was investigated in CNE2 human epithelial tumor cells. Induction of these cells to undergo apoptosis with staurosporine was associated with a massive increase in intracellular cAMP level. The inhibition of the increase in cAMP partially inhibited apoptosis as evidenced by a reduction of PARP and caspase-3 cleavage. Accordingly, a low but significant level of apoptosis is induced in these cells by the elevation of cAMP through the addition of forskolin and isobutylmethylxanthine. The existence of a cAMP-dependent and a cAMP-independent apoptotic pathway is therefore suggested. Receptor binding studies, RT-PCR experiments and Western blot analysis demonstrated the presence of type 1 kappaor in the CNE2 cells. Stimulation of kappaor in these cells resulted in the production of inositol (1,4,5)-trisphosphate, reduction of cAMP level and a marked enhancement of staurosporine-induced apoptosis. The potentiation of apoptosis by kappaor was prevented by inhibition of phospholipase C but was slightly enhanced by the presence of the active cAMP analogues, 8-CPT-cAMP and dibutyryl-cAMP. These data demonstrate for the first time that the phospholipase C pathway activated by type 1 kappaor expressed by cancer cells is involved in the potentiation of apoptosis.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adenine; Apoptosis; Base Sequence; Benzomorphans; Cell Membrane; Colforsin; Cyclic AMP; Dideoxyadenosine; Drug Synergism; Epithelial Cells; Estrenes; Humans; Molecular Sequence Data; Pyrrolidinones; Receptors, Opioid, kappa; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Staurosporine; Tumor Cells, Cultured; Type C Phospholipases

8-Methyl-N-vanillyl-6-nonenamide (capsaicin) was locally applied in the tail of rhesus monkeys to evoke a nociceptive response, thermal allodynia, which was manifested as reduced tail-withdrawal latencies in normally innocuous 46 degrees C water. Coadministration of three kappa opioid ligands, U50,488 (3.2-100 microgram), bremazocine (0.1-3.2 microgram), and dynorphin A(1-13) (3.2-100 microgram), with capsaicin in the tail dose-dependently inhibited capsaicin-induced allodynia. This local antinociception was antagonized by a small dose of an opioid antagonist, quadazocine; (0.32 mg), applied in the tail; however, this dose of quadazocine injected s.c. in the back did not antagonize local U50,488. Comparing the relative potency of either agonist or antagonist after local and systemic administration confirmed that the site of action of locally applied kappa opioid agonists is in the tail. In addition, local nor-binaltorphimine (0.32 mg) and oxilorphan (0.1-10 microgram) antagonist studies raised the possibility of kappa opioid receptor subtypes in the periphery, which indicated that U50,488 produced local antinociception by acting on kappa1 receptors, but bremazocine acted probably on non-kappa1 receptors. These results provide functional evidence that activation of peripheral kappa opioid receptors can diminish capsaicin-induced allodynia in primates. This experimental pain model is a useful tool for evaluating peripherally antinociceptive actions of kappa agonists without central side effects and suggests new approaches for opioid pain management.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Azocines; Benzomorphans; Capsaicin; Dynorphins; Female; Hot Temperature; Ligands; Macaca mulatta; Male; Naltrexone; Narcotic Antagonists; Pain Measurement; Peptide Fragments; Receptors, Opioid, kappa

To explore the existence of multiplicity of kappa receptor in the heart, two series of experiments were performed. In the first we studied the antagonistic actions of nor-BNI, a selective kappa 1 antagonist, and quadazocine, a preferential kappa 2 antagonist, against the effects of U50488, a selective kappa 1 agonist, and bremazocine, a universal agonist preferentially binding to kappa 2 receptor, on the electrically stimulated [Ca2+]i transient and forskolin-stimulated cAMP accumulation in the rat ventricular myocyte. In the second series of experiments, we determined and compared the effects of above two kappa receptor agonists in the ventricular myocytes made insensitive to kappa 1 and kappa 2 agonists by prior exposure to the respective agonists. At the concentration range of 3 x 10(-6)-3 x 10(-5) M, both U50488 and bremazocine dose-dependently inhibited the [Ca2+]i transient induced by electrical stimulation. The inhibitory effects of U50488 and bremazocine were antagonized by nor-BNI and quadazocine. The antagonistic actions of nor-BNI were significantly greater against the effects of U50488, but smaller against the effects of bremazocine than those of quadazocine. At 1 x 10(-6)-5 x 10(-5) M, both U50488 and bremazocine dose-dependently and significantly inhibited the forskolin-induced cAMP accumulation. The inhibitory effect of 30 microM U50488 on cAMP accumulation was significantly attenuated by 5 microM nor-BNI, but not by quadazocine at the same concentration; whereas the effect of 30 microM bremazocine was significantly blocked by 5 microM quadazocine, but not by nor-BNI at the same concentration. The inhibitory effect of 30 microM U50488 on electrically stimulated [Ca2+]i was abolished by preincubation of myocytes with 10(-6) M U50488 for 24 h, but not with 10(-6) M bremazocine for h; whereas the inhibitory effect of 30 microM bremazocine on electrically stimulated [Ca2+]i transient was significantly attenuated after incubation of the myocyte with 10(-6) M bremazocine for 24 h, but not with 10(-6) M U50488 for 24 h. The observations indicate the existence of kappa receptor subtypes in the rat heart.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Azocines; Benzomorphans; Calcium; Cells, Cultured; Colforsin; Cyclic AMP; Drug Resistance; Electric Stimulation; Heart; Heart Ventricles; Male; Naltrexone; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa

It has been postulated that opioid systems in the brain may play a role in ethanol reinforcement. In this respect, mu- and delta-opioid receptors may mediate the rewarding effects whereas kappa receptors are thought to mediate the aversive effects of opioids. Accordingly, long-acting benzomorphans such as bremazocine, that simultaneously act as mu and delta receptor antagonists and kappa receptor agonists may be particularly effective in reducing ethanol self-administration. Therefore, we studied the effect of bremazocine on oral ethanol self-administration in rats using a paradigm [unrestricted free-choice drinking of 10% (v/v) ethanol], previously shown to cause long-term neuroadaptations in the nucleus accumbens and caudate putamen. Bremazocine (0.1 mg/kg, once daily for five consecutive days) reduced ethanol drinking by about 50% during the active period of the animals, whereas the intake of sucrose (3-10% w/v) was affected neither in naive nor in ethanol-experienced rats. This effect of bremazocine appeared not to be secondary to its acute sedative effect or the slight increase in total fluid consumption. Unlike bremazocine, the selective kappa-opioid receptor agonist U50,488H (10 mg/kg, once daily) inhibited ethanol drinking only during the first of 5 treatment days and the opioid receptor antagonist naltrexone (0.3-10 mg/kg, once daily) only caused a modest (about 20%) suppression of ethanol drinking during the first hours after drug injection. Thus, bremazocine appears to be far more potent than the clinically applied drug naltrexone in this respect. Our data further support the role of opioid receptors in ethanol reinforcement and indicate that long-acting mixed-action opioids such as bremazocine may be useful as adjuvants for the clinical management of ethanol addiction.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Alcohol Drinking; Alcoholism; Animals; Benzomorphans; Ethanol; Male; Motor Activity; Naltrexone; Narcotic Antagonists; Rats; Rats, Wistar; Receptors, Opioid; Reinforcement, Psychology; Self Administration; Sucrose

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 kappa 1 and kappa 2 opioid receptor agonists U-62066 (8 mg/kg, i.p.) and (-)-bremazocine (0.7 mg/kg, i.v.), respectively, both exhibit anti-arrhythmic properties against adrenaline-induced dysrhythmias in rats. 2. In contrast, (+)-bremazocine has no effect on adrenaline-induced dysrhythmias. 3. The kappa 1 opioid receptor agonists U-50488 (110 nmol) and [D-Ala2]-dynorphin A (20 nmol) and the kappa 2 opioid receptor agonist (-)-bremazocine (30 nmol) exhibit pro-arrhythmic properties following intracerebroventricular administration. 4. Prior administration of the kappa opioid receptor antagonist nor-binaltorphimine doses i.c.v. (14 nmol), i.p. (10 mg/kg), completely abolishes the pro-arrhythmic (BNI, i.c.v., 14 nmol) as well as anti-arrhythmic (BNI, 10 mg/kg, i.p.) effects of the kappa opioid receptor agonists. 5. Neither hexamethonium (10 mg/kg, i.v.) nor atropine (1 mg/kg, i.v.) have any effect on the anti-arrhythmic actions of the kappa 1 opioid receptor agonist U-62066 following systemic administration. 6. It is suggested that the anti-arrhythmic effects of U-62066 and (-)-bremazocine are associated with the activation of peripheral kappa opioid receptors and do not depend on the activation of kappa opioid receptors in the autonomic nervous system.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anti-Arrhythmia Agents; Antihypertensive Agents; Arrhythmias, Cardiac; Benzomorphans; Dynorphins; Male; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa

Systemic administration of nor-binaltorphimine (nor-BNI) produces a long-lasting kappa-opioid receptor (kappaOR) antagonism and has kappa(1)-selectivity in nonhuman primates. The aim of this study was to establish the pharmacological basis of central kappaOR antagonism in rhesus monkeys (Macaca mulatta). After intracisternal (i.c.) administration of small doses of nor-BNI, the duration and selectivity of nor-BNI antagonism were evaluated against two kappaOR agonists, (trans)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide (U50,488) and bremazocine. Thermal antinociception was measured in the warm water (50 degrees C) tail-withdrawal assay and sedation was evaluated by observers blind to treatment conditions. Following i.c. pretreatment with 0.32 mg nor-BNI, a 5- to 10-fold rightward shift of the U50,488 baseline dose-effect curve was observed in antinociception. In contrast, this dose of nor-BNI only produced an insignificant 2-fold shift against bremazocine. Pretreatment with a smaller dose (0.032 mg) of nor-BNI produced a 3-fold shift of U50, 488, which lasted for 7 days, but failed to alter the potency of bremazocine. This differential antagonism profile of i.c. nor-BNI also was observed in sedation ratings. In addition, the centrally effective dose of nor-BNI (0.32 mg), when administered s.c. in the back, did not antagonize either U50,488- or bremazocine-induced antinociception and sedation. After i.c. pretreatment with the same dose, nor-BNI also did not antagonize the peripherally mediated effect of U50,488 against capsaicin-induced thermal nociception in the tail. These results indicate that i.c. nor-BNI produces central kappaOR antagonism and support the notion of two functional kappaOR subtypes in the central nervous system. Moreover, it provides a valuable pharmacological basis for further characterizing different sources of kappaOR-mediated effects, namely, from central or peripheral nervous system receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Opioid; Animals; Benzomorphans; Central Nervous System; Cisterna Magna; Dose-Response Relationship, Drug; Female; Hot Temperature; Injections; Macaca mulatta; Male; Naltrexone; Narcotic Antagonists; Peripheral Nervous System; Receptors, Opioid, kappa

The behavioral response of planaria to the exposure to selective opioid agonists was studied. The mu agonist [d-ala2, N-methyl-Phe4,Gly5-ol]enkephalin (DAMGO) and the 6 agonist [D-Pen2, D-Pen5]enkephalin (DPDPE) failed to alter motor activity at all doses tested. Low doses of the selective kappa agonist (+/-)-trans-U-50-trans-3,4-dichloro-N-methyl-N[2-(1-pyrrodinyl)-cyclohexyl]benzene acetamide methasulphonate (U50, 488) and bremazocine-HCl increased motor activity leading to C-like position (CLP) and screw-like hyperkinesia (SLH). These changes were identical to those seen previously with the exposure to D2 or D1 dopamine receptor agonists, respectively. Higher doses of kappa agonists produced the enhancement of CLP and SLH together with robust snake-like movements (SLM). This latter response, that was typical of stimulation of kappa opioid receptors, was blocked by co-exposure to naloxone or the selective kappa antagonist Nor-binaltorphimine (Nor-BNI). Finally, co-exposure to sulpiride or SH-23390 respectively blocked the CLP or SLH response produced by U50,488 or bremazocine. Our data indicate the presence of kappa opioid receptors in planaria and suggest the functional interaction between the opioid and dopamine system in this simple animal model.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Dopamine; Dopamine Antagonists; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Motor Activity; Narcotic Antagonists; Planarians; Receptors, Opioid; Receptors, Opioid, kappa; Sulpiride

This study delineates the heterotrimeric guanine nucleotide binding regulatory protein (G-protein) types in frog (Rana esculenta) brain membranes and their activation by kappa opioid agonists. Ethylketocyclazocine (EKC), trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)b enzeneacetamide (U-50,488) and bremazocine displayed dose-dependent, norbinaltorphimine-reversible stimulation of guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding in crude membrane preparations. G-proteins were identified by Western-blotting using previously characterized specific antisera that were generated against mammalian G-protein alpha-subunits and beta-subunits. A photoreactive guanosine 5'-triphosphate (GTP) analog, [alpha-32P]GTP azidoanilide ([alpha-32P]AA-GTP) irreversibly labeled four proteins in the molecular weight range of 39-43 kDa. Ethylketocyclazocine and U-50,488 stimulated photolabelling of these proteins among which the 39 kDa band comigrated with the protein specifically labelled with the alpha(i2) antibody and the 40 kDa band was identified as alpha(o1). The other two bands were also stained with the alpha(common) antibody, but were not further identified. These results suggest that the endogenously expressed kappa opioid receptors that are present in frog brain interact with multiple G-proteins in situ. Furthermore, the structure of most G-proteins seems to be well preserved during phylogenesis.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Brain; Cell Membrane; Ethylketocyclazocine; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Kinetics; Naltrexone; Narcotic Antagonists; Rana esculenta; Receptors, Opioid, kappa

Comparative centrally mediated hypotensive effects of three nonpeptide kappa opioid agonist drugs (bremazocine, spiradoline, and U-50,488H) were evaluated in chloralose-anesthetized male spontaneously hypertensive rats (SHRs) and in normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats. The drugs were administered unilaterally into previously established active hypotensive sites in the dorsal hippocampus at doses of 12, 24, and 48 nmol. Each drug produced dose-related decreases in mean arterial pressure, ranging from -5 to -40% of predrug control values, with bremazocine being somewhat more effective than spiradoline, which was in turn slightly more active than U-50,488H. The effects were only marginally greater in SHRs than in normotensive controls. Each drug caused a modest decrease in heart rate, but except for the highest dose of bremazocine, the effects were not statistically significant. The onset of hypotension after intrahippocampal injection of each agent was approximately 2 min and lasted approximately 30 min with U-50,488H and spiradoline and >60 min with bremazocine. The responses to all three drugs were completely blocked by prior injection of the active hippocampal sites with nor-binaltorphimine (nor-BNI), a selective kappa-receptor antagonist. Because bremazocine is more selective for kappa-2 opioid receptors, whereas U-50,488H and spiradoline favor the kappa-1 subtype, the results suggest that drugs active on each of these subtypes should be investigated as potential antihypertensives.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Antihypertensive Agents; Benzomorphans; Dose-Response Relationship, Drug; Hippocampus; Male; Naltrexone; Narcotic Antagonists; Pyrrolidines; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Opioid, kappa

Although only one gene for kappa opioid receptors has been cloned to date, kappa1 and kappa2 receptors have been defined pharmacologically, with drugs such as bremazocine binding to both putative kappa receptor subtypes. To examine whether kappa receptor subtypes can be distinguished at the level of the G-protein, the ability of the kappa1 agonist (trans-(dl)-3,4-dichloro-N- methyl-N-[2-(1 -pyrrolidinyl)cyclohexyl]-benzeneacetamide) methane sulfonate (U-50488H) to stimulate [35S]guanosine-5'-O-(gamma-thio)-triphosphate ([35S]GTPgammaS) binding in guinea pig brain was compared with that of bremazocine and dynorphin. In membranes prepared from guinea pig striatum, both bremazocine and U-50488H stimulated [35S]GTPgammaS binding with the same relative efficacy, while dynorphin produced at least two-fold greater efficacy than the other two agonists. In vitro autoradiography of agonist-stimulated [35S]GTPgammaS binding revealed similar regional distributions of bremazocine- and U-50488H-activated G-proteins. In striatal membranes, the kappa antagonist nor-binaltorphimine (nor-BNI) blocked both bremazocine- and U-50488H-stimulated [35S]GTPgammaS binding with similar Ke values. In agonist additivity experiments, the stimulation of [35S]GTPgammaS binding by the delta agonist [D-pen2'5, p-Cl-Phe4]enkephalin (p-Cl-DPDPE) was approximately additive with the two kappa agonists. Stimulation of [35S]GTPgammaS binding by the mu agonist [D-Ala2, N-Me4, Gly5-ol]-enkephalin (DAMGO) was additive with U-50488H, but not with bremazocine, reflecting the mu antagonist properties of this compound. The combination of bremazocine and U-50488H together produced no greater stimulation of binding than either agonist alone, indicating that they were binding to the same site. These results demonstrate that bremazocine and U-50488H activate G-proteins in guinea pig brain through the same receptor, and suggest that kappa2 receptors are not coupled through the same signal transduction mechanisms as kappa1 receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Autoradiography; Benzomorphans; Brain; Dynorphins; Guanosine 5'-O-(3-Thiotriphosphate); Guinea Pigs; In Vitro Techniques; Male; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Sulfur Radioisotopes

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

The blockade of veratrine-stimulated phosphoinositide breakdown in rat cerebral cortical miniprisms has been used as a model of drug action on voltage-dependent sodium channels. The kappa-opioid agonists bremazocine, (+/-)- and (+)-trans-U-50488, U-62066 (spiradoline) and U-69593 inhibited the response to veratrine with IC50 values of 35, 13, 15, 9, and > 100 microM, respectively. Bremazocine, at concentrations inhibiting the response to veratrine, did not inhibit the phosphoinositide breakdown response to the sodium ionophore monensin, indicating the specificity of the assay for sodium channels. The inhibitory actions of bremazocine upon veratrine-stimulated phosphoinositide breakdown were not antagonised by naloxone. This study thus confirms previous data suggesting that the kappa-opioid receptor agonists can affect Na(+)-channel function in a manner unrelated to their actions at kappa-opioid receptors. However, for the compounds tested, such effects are only found at rather high concentrations of the compounds.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Brain; Disease Models, Animal; Inositol Phosphates; Naloxone; Pyrrolidines; Rats; Receptors, Opioid, kappa; Sodium Channels

This study describes the coupling of the recombinant rat kappa-opioid receptor expressed in Chinese hamster ovary (CHO) cells to adenylyl cyclase and the effects of receptor density. The binding of [3H]diprenorphine ([3H]DPN) was dose dependent and saturable in membranes prepared from cells of early (p4-7) and late (p14-17) passage after transfection. As passage increased the receptor numbers (Bmax) declined from 231 +/- 24 (early) to 31 +/- 2 fmol/mg protein (late) but the equilibrium dissociation constant (Kd) did not change. Spiradoline dose dependently displaced [3H]DPN from membranes prepared from early and late cells revealing both high (Ki[H]) and low (Ki[L]) affinity binding sites. There were no significant differences in the proportion of these sites (approximately 50% Ki(L):50% Ki[H]), and whilst spiradoline was generally less potent in late cells the differences were small and failed to reach statistical significance. In contrast, spiradoline produced a dose dependent inhibition of forskolin stimulated cAMP formation in whole cells with pIC50 of 8.62 and 8.00 in early compared with late cells. In addition, the maximum inhibition was dramatically reduced from 47 to 22%. Etorphine, (+/-)bremazocine, ICI-204,448 and (+/-)trans-U-50488 methanesulfonate (1 microM), compounds with activity at kappa-receptors, produced a greater inhibition of cAMP formation in early (42.2, 45.8, 50.2 and 50.5%, respectively) than late (12.9, 11.8, 13.5 and 7.8%, respectively) cells, indicating that expression dependent inhibition of cAMP formation was not kappa-agonist specific. Collectively, these data suggest that in CHO cells, kappa-opioid receptor coupling to adenylyl cyclase is dependent on receptor expression levels.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adenylyl Cyclases; Analgesics; Animals; Benzomorphans; CHO Cells; Colforsin; Cricetinae; Cyclic AMP; Diprenorphine; Dose-Response Relationship, Drug; Etorphine; Gene Expression; Narcotic Antagonists; Phosphodiesterase Inhibitors; Pyrrolidines; Rats; Receptors, Opioid, kappa; Transfection

Cocaine is thought to be addictive because chronic use leads to molecular adaptations within the mesolimbic dopamine (DA) circuitry that affect motivated behavior and emotion. Although the reinforcing effects of cocaine are mediated primarily by blocking DA reuptake into the presynaptic nerve terminal, reciprocal signaling between DA and endogenous opioids has important implications for cocaine dependence. The present study used the opioid antagonist 6 beta-[125iodo]-3,14-dihydroxy-17-cyclopropylmethyl-4,5 alpha-epoxymorphinan ([125I]IOXY) after pretreatment with the site-directed acylating agents 2-(p-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimid iazole -HCl (mu-selective) and N-phenyl-N-[1-(2-(4-isothiocyanato)-phenethyl)-4-piperidinyl]-p ropana mide-HCl (delta-selective) to examine the effect of cocaine exposure on the distribution and density of kappa2 receptors in autopsy studies of human cocaine fatalities. The selective labeling of the kappa2 receptor subtype was demonstrated by competition binding studies, which gave a pharmacological signature (IOXY >/= (+)-bremazocine >> U50,488 >/= U69,593) distinct from either the kappa1 or kappa3 receptor subtypes. Visualization of [125I]IOXY labeling revealed that kappa2 receptors localize to mesocortical and subcortical limbic areas, including the cingulate, entorhinal, insular, and orbitofrontal cortices and the nucleus accumbens and amygdala. The number of kappa2 receptors in the nucleus accumbens and other limbic brain regions from cocaine fatalities was increased twofold as compared with age-matched and drug-free control subjects. Cocaine overdose victims, who experienced paranoia and marked agitation before death, also had elevated densities of kappa2 receptors in the amygdala. These findings demonstrate for the first time that kappa2 receptor numbers are upregulated by cocaine exposure. The molecular adaptation of kappa2 receptor numbers may play a role in the motivational incentive associated with episodes of binge cocaine use and in the dysphoria that follows abrupt cocaine withdrawal.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adult; Amygdala; Benzeneacetamides; Benzomorphans; Binding, Competitive; Brain; Brain Chemistry; Caudate Nucleus; Cocaine; Dopamine; Dopamine Uptake Inhibitors; Drug Overdose; Female; Fentanyl; Gyrus Cinguli; Humans; Isothiocyanates; Kinetics; Male; Morphinans; Protein Binding; Pyrrolidines; Receptors, Opioid, kappa; Tissue Distribution; Up-Regulation

The present study examined whether the kappa-opioid agonists U50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N[-2-(1-pyrrolidinyl)- cyclohexyl]-benzeacetamide methane sulphonate), bremazocine, spiradoline and ICI 197067 bind to sigma sites in guinea-pig tissues using in vitro, semi-quantitative receptor autoradiography and receptor binding, and compared the binding profile so obtained with those for several selective sigma ligands. Guinea-pigs were killed and their brians, livers and spleens were removed, tissue sections cut and processed for sigma binding site autoradiography using (+)-[3H]-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-[3H]-3-PPP), or tissue was wiped and determined by liquid scintillation. Serial slide-mounted sections were incubated with 9-10 concentrations (1 nM-10 microM) of kappa opioids and their potency to inhibit (+)-[3H]-3-PPP binding compared with that of the sigma ligands haloperidol, DTG (1,3 di(o)-tolylguanidine), (+)-3-PPP, (+) and (-)pentazocine, SR 31742A and rimcazole (n = 3, duplicate determinations). Binding of (+)-[3H]-3-PPP to untreated, matched serial tissue sections was used as control. Kd values were estimated in brain, liver and spleen using quantitative, saturation binding analysis, IC50 values were determined from the binding data obtained by slide wiping experiments for each drug, and Ki values were calculated using the Cheng-Prussoff equation. All four kappa opioids inhibited (+)-[3H]-3-PPP binding to sigma 1-receptors with order of potency: brain: U50,488H = spiradoline > bremazocine > ICI 197067; liver: spiradoline > U50,488H > ICI 197067 > bremazocine; spleen: U50,488H > spiradoline > ICI 197067 > bremazocine. By comparison, the sigma ligands inhibited (+)-[3H]-3-PPP binding to matched, serial slide-mounted brain tissue sections (similar results in liver and spleen) with order of potency: SR 31742A > haloperidol > (+)pentazocine > (+)-3-PPP > DTG > (-)pentazocine > rimcazole. (+)-[3H]-3-PPP autoradiography confirmed these binding data. It is concluded that the kappa opioids tested moderately inhibit (+)-[3H]-3-PPP binding to sigma 1-receptors in guinea-pig brain, liver and spleen tissue with Ki values comparable to some selective sigma ligands and therefore are not opioid selective.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Autoradiography; Benzomorphans; Binding Sites; Brain; Guinea Pigs; Liver; Piperidines; Pyrrolidines; Receptors, Opioid, kappa; Receptors, sigma; Spinal Cord; Spleen

The mouse thymoma R1.1 cell line was shown previously to express a single high-affinity kappa 1 opioid receptor that is negatively coupled through a pertussis toxin-sensitive G-protein to adenylyl cyclase. This study compared opioid receptor binding and inhibition of adenylyl cyclase activity in three unique derivatives of the R1.1 cell line. Membranes from the R1.G1 and R1E/TL8x.1.G1.OUAr.1 (R1EGO) cell lines bound both [3H]U69,593 and [3H](-)-bremazocine with similar affinities compared with R1.1 membranes, whereas membranes from the R1E/TL8x.1 (R1E) cell line did not possess any opioid binding sites, detected by radioreceptor binding. The Bmax values for [3H]U69,593 and [3H]-(-)-bremazocine binding to R1.G1 and R1EGO cell membranes were, respectively, 3- and 6-fold greater than those obtained with the parent R1.1 cell line. GTP and its nonhydrolyzable analog, Gpp(NH)p, inhibited [3H]U69,593 binding to all three cell lines. Stimulation of low-Km GTPase activity by the kappa-selective agonist (-)U50,488 was greatest in R1.G1 membranes, followed by R1EGO and R1.1. The maximal inhibition of forskolin-stimulated adenylyl cyclase activity by (-)U50,488 was 66 +/- 2% in R1.G1 and 49 +/- 2% in R1EGO, compared with 37 +/- 1% in R1.1 membranes. Whereas maximal inhibition of adenylyl cyclase activity did not correlate with receptor number among cell lines, the inhibition of cyclic AMP production did correlate with stimulation of low-Km GTPase activity. The R1.1 cell line and its derivatives, R1.G1 and R1EGO, express a similar type of kappa opioid receptor, which exhibits differences in coupling to G-proteins and to adenylyl cyclase among cell lines. These cell lines provide an excellent model system for studying the regulation of opioid receptor-adenylyl cyclase coupling efficiency.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Cell Membrane; GTP Phosphohydrolases; Kinetics; Mice; Pyrrolidines; Receptors, Opioid, kappa; Thymoma; Thymus Neoplasms; Tumor Cells, Cultured

The ability of mu and kappa opioids to alter the discriminative-stimulus and rate-decreasing effects of the 5-HT1A receptor agonist 8-OH-DPAT was examined in rats trained to discriminate either a low (0.1 mg/kg) or a high (0.3 mg/kg) dose of 8-OH-DPAT from water using a two-lever food-reinforced drug discrimination procedure. The mu opioids, morphine and fentanyl, and the kappa opioids, U50,488 and bremazocine, failed to substitute for the 8-OH-DPAT stimulus, even when tested up to doses that substantially reduced rates of responding. During antagonism tests, selected doses of the mu opioids, morphine and fentanyl, administered at various pretreatment times, attenuated the stimulus effects of both training doses of 8-OH-DPAT. Moreover, morphine (135-min pretreat) and fentanyl (15-min pretreat) produced rightward shifts in the 8-OH-DPAT dose-effect curve that were partially surmountable and naltrexone-reversible. In contrast to the effects of the mu opioids, the kappa opioids, U50,488 and bremazocine, failed to alter the stimulus effects of the training dose of 8-OH-DPAT, regardless of dose or pretreatment time. The rate-decreasing effects of 8-OH-DPAT were not altered substantially by either the mu or kappa opioids examined. The present study demonstrates that the stimulus effects, but not the rate-decreasing effects, of 5-HT1A receptor agonists can be modulated by mu opioids, whereas neither of these effects are changed by kappa opioids.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; 8-Hydroxy-2-(di-n-propylamino)tetralin; Analgesics; Animals; Benzomorphans; Discrimination Learning; Drug Therapy, Combination; Fentanyl; Male; Morphine; Narcotics; Pyrimidines; Pyrrolidines; Rats; Receptors, Opioid, kappa; Receptors, Opioid, mu; Serotonin Receptor Agonists

The purpose of the present series of experiments was to analyze the effects of morphine and naloxone on sexual behavior in the male rabbit, and to evaluate the role of central and peripheral opioid receptors. Morphine was found to inhibit sex behavior in a dose dependent way. The effects were slight at 5 min postinjection. At 1 hr all aspects of sexual behavior were reduced. This effect lasted at least until 3 hrs postinjection. Subcutaneous (s.c.) injection produced effects at lower doses than intraperitoneal (i.p.) injection. Minimal effective doses were 1.25 and 5 mg/kg, respectively. Naloxone also inhibited sexual behavior. Again, s.c. administration had effects at lower doses than i.p. administration (0.25 vs 16 mg/kg). The effects of morphine were reduced but not completely antagonized by several doses of naloxone, independently of whether s.c. or i.p. administration were used. An opioid kappa agonist, bremazocine, inhibited sexual behavior at a low dose (30 micrograms/kg). It is suggested that the inhibitory effects of morphine may be mediated by the kappa receptor. A peripheral opioid antagonist, methylnaloxone, had no effects by itself and was unable to modify the effects of morphine. It is concluded that the effects of morphine are localized within the central nervous system. This is further supported by the observation that loperamide, a peripheral opiate agonist, had only marginal effects on sex behavior.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Central Nervous System; Dose-Response Relationship, Drug; Ejaculation; Female; Injections, Intraperitoneal; Injections, Subcutaneous; Loperamide; Male; Morphine; Naloxone; Narcotics; Oxymorphone; Peripheral Nervous System; Pyrrolidines; Rabbits; Receptors, Opioid; Receptors, Opioid, kappa; Sexual Behavior, Animal

By screening a rat brain cDNA library using a cloned mu opioid receptor cDNA as probe, a clone was identified that is very similar to both the mu and delta opioid receptor sequences. Transient expression of this clone in COS-7 cells showed that it encodes a kappa opioid receptor, designated KOR-1, which is capable of high-affinity binding to kappa-selective ligands. Treatment of transfected cell membranes with bremazocine, a kappa-selective agonist, resulted in a 53% decrease in adenylate cyclase activity, indicating that this kappa opioid receptor displays inhibitory coupling to adenylate cyclase. Thus, one member from each of the three opioid receptor types, mu, kappa and delta, has been molecularly cloned. Analysis of sequence similarities among these opioid receptors, as well as between opioid receptors and other G-protein-coupled receptors, revealed regions of sequence conservation that may underlie the ligand-binding and functional specificities of opioid receptors.

Topics: Adenylyl Cyclases; Amino Acid Sequence; Animals; Benzomorphans; Cloning, Molecular; Diprenorphine; DNA, Complementary; Molecular Sequence Data; Rats; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Sequence Analysis; Sequence Homology, Amino Acid; Transfection

Previous reports show the tail-flick inhibition induced by bremazocine given i.c.v. is mediated by supraspinal stimulation of both epsilon and kappa opioid receptors and the spinal activation of descending serotonergic and opioid systems. The present studies questioned what endogenous opioid peptides in the spinal cord were involved in i.c.v. bremazocine-induced antinociception in male ICR mice. beta-Endorphin, trans(+-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]- benzene-acetamide methane sulfonate (U50,488H) and morphine were used as reference compounds for epsilon, kappa and mu opioid receptor activity, respectively. Intrathecal pretreatment with antibody to Met-enkephalin dose-dependently attenuated the antinociception induced by i.c.v. bremazocine or beta-endorphin but not morphine or U50,488H; whereas intrathecal (i.t.) pretreatment with antibody to dynorphin A (1-13) dose-dependently blocked the antinociception induced by i.c.v. bremazocine or U50,488H but not beta-endorphin or morphine. Intrathecal Leu-enkephalin and beta-endorphin antibodies did not block i.c.v. bremazocine, beta-endorphin or morphine antinociception. Intrathecal Met-enkephalin or dynorphin A (1-17) increased the tail-flick latency at 1 to 2 min. Met-enkephalin given i.t. blocked the antinociception induced by i.c.v. DPDPE, bremazocine and beta-endorphin but not morphine or U50,488H whereas i.t. dynorphin A (1-17) pretreatment blocked the inhibition induced by i.c.v. U50,488H and bremazocine but not DPDPE, beta-endorphin or morphine. Bremazocine given i.c.v. did not exhibit antianalgesic activity in our studies. The dynorphin released by i.c.v. bremazocine for antinociception appears to be different from the dynorphin released by morphine for antianalgesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Animals; Benzomorphans; beta-Endorphin; Drug Interactions; Dynorphins; Enkephalin, Leucine; Enkephalin, Methionine; Injections, Intraventricular; Male; Mice; Mice, Inbred ICR; Morphine; Nociceptors; Pain Measurement; Pyrrolidines; Spinal Cord; Time Factors

The present study was conducted to evaluate the agonist and antagonist properties of kappa opioids in the squirrel monkey shock titration procedure. The opioid antagonist naltrexone, the kappa agonists U50,488, bremazocine, ethylketazocine and tifluadom, and the mu agonist l-methadone were administered alone and in combination with a single dose of the mu agonist morphine. When administered alone, all opioids except naltrexone produced dose-dependent increases in median shock level (the intensity below which monkeys maintained shock 50% of the time). In addition, all kappa agonists produced increases in urine output, whereas naltrexone and l-methadone did not. When combined with morphine, naltrexone and all kappa agonists antagonized, at least partially, morphine-induced increases in median shock level, whereas l-methadone did not. Naltrexone and the four kappa agonists also shifted an l-methadone dose-effect curve rightward in a parallel manner; however, the shifts produced by naltrexone were greater in magnitude than those produced by the kappa agonists. These studies demonstrate that a variety of kappa agonists can act as mu antagonists in a primate model of analgesia, although antagonist activity of kappa opioids appears to be limited by their agonist activity in this procedure. Order of potency among the kappa agonists for analgesic, diuretic and antagonist effects was very similar (bremazocine greater than ethylketazocine greater than tifluadom greater than or equal to U50,488), as was the dose range for peak diuretic and antagonist effects, suggesting that mu antagonism among kappa agonists may be kappa-mediated in the squirrel monkey.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Behavior, Animal; Benzodiazepines; Benzomorphans; Drug Interactions; Ethylketocyclazocine; Male; Methadone; Morphine; Naltrexone; Narcotic Antagonists; Narcotics; Nociceptors; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Saimiri; Urination

The kappa opioid agonists U50,488, bremazocine, ethylketazocine and tifluadom and the opioid antagonist naltrexone were examined alone and in combination with morphine in a squirrel monkey shock titration procedure, before and during chronic morphine administration. Before chronic morphine administration (prechronic phase), all opioids except naltrexone produced dose-dependent increases in median shock level when administered alone. When combined with a dose of morphine that increased median shock level to 90% of maximum (ED90), naltrexone, U50,488 and bremazocine completely antagonized the effects of morphine in most monkeys, whereas ethylketazocine and tifluadom partially antagonized the effects of this dose of morphine. After 10 weeks of daily morphine administration (chronic phase), the average ED90 for morphine was increased 1 log unit. In contrast, average ED50 values for U50,488, bremazocine and tifluadom were decreaed 1/4 to 1/2 log unit, whereas the average ED50 for ethylketazocine did not change from the prechronic to chronic phases. When combined with morphine during the chronic phase, naltrexone completely antagonized the effects of the morphine ED90 at approximately the same doses as during the prechronic phase. In contrast, antagonist activity decreased for U50,488 and bremazocine, increased for ethylketazocine and did not change consistently for tifluadom, compared with the prechronic phase. The present study demonstrates that chronic morphine administration alters both the agonist and antagonist activity of kappa opioids. Changes in antagonist activity of kappa opioids after chronic morphine administration may be explained by concurrent changes in their agonist potency and the extent to which their agonist effects are mu-mediated.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzodiazepines; Benzomorphans; Drug Interactions; Drug Tolerance; Ethylketocyclazocine; Male; Morphine; Naltrexone; Narcotic Antagonists; Narcotics; Nociceptors; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Saimiri; Shock; Time Factors

1. It has recently been suggested that opioid antagonists may be divided into those possessing negative intrinsic activity (e.g. naloxone) and those with neutral intrinsic activity (e.g. MR2266). 2. MR2266 was chronically administered to rats by subcutaneous infusion at a dose of 0.3 mg kg-1 h-1 for 1 week. 3. This dose reduced ingestive behaviour and blocked the antinociceptive effects of a kappa-agonist, indicating occupation of opioid receptors in vivo. 4. No supersensitivity could be detected to the antinociceptive actions of mu or kappa agonists, either one or two days after cessation of treatment. 5. No up-regulation of mu, delta or kappa binding sites was observed. 6. Since naloxone induces both supersensitivity and receptor up-regulation under equivalent conditions, the results suggest that negative intrinsic activity may be required for these phenomena to occur.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Binding, Competitive; Drinking; Eating; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine-2-Alanine; Enkephalins; Male; Narcotic Antagonists; Pain; Pain Measurement; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Sensory Thresholds; Up-Regulation

Opioid peptides have been implicated in shock-associated hypotension. Our aim was to find out whether opioid agonists have direct vasodilator actions on vascular smooth muscle. The study was conducted on rat abdominal aortic rings. In rings precontracted with either norepinephrine, prostaglandin F2 alpha, or high potassium Krebs (HPK), the effects of the opioid agonists tested (morphine, U50488H, ethylketocyclazocine (EKC), and bremazocine) depended on the precontracting agent used. HPK-precontracted rings were relaxed by all agonists tested. In norepinephrine-precontracted rings, all caused contraction at low concentrations and relaxation at high concentrations except bremazocine, which caused only relaxation. In prostaglandin F2 alpha-precontracted rings, U50488H produced contraction at low concentrations and relaxation at high concentrations while EKC caused only relaxation and morphine or bremazocine caused only contraction. All relaxant responses were endothelium-independent and were antagonized by verapamil but not by a number of antagonists including naloxone. MR2266, propranolol, diphenhydramine, cimetidine, and indomethacin. They may reflect calcium channel blockade. Morphine-induced vasoconstriction was antagonized by high concentrations of of naloxone or mepyramine and may be due to release of histamine by a naloxone-sensitive mechanism. We conclude that (a) the opioid agonists tested exert direct actions on vascular smooth muscle; (b) the nature of the response depended not only on the agonist used and its concentration but also on the agent used to precontract the tissue; and (c) it is unlikely that direct actions of endogenous opioids contribute to the shock-associated hypotension because high doses were needed to elicit them.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Calcium Channel Blockers; Dinoprost; Endothelium, Vascular; Ethylketocyclazocine; In Vitro Techniques; Male; Morphine; Muscle Contraction; Muscle, Smooth, Vascular; Narcotic Antagonists; Norepinephrine; Potassium; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Vasodilation

The analgesic effects of mu- and kappa-opioid agonists, including morphine, FK33,824, U50,488H, tifluadom and bremazocine, have been determined in C57BL/6J-bgJ (beige) and CXBK mice which are hyporesponsive to mu-opioid receptor-mediated analgesia compared with those of control mice (C57BL/6J (C6J), C57BL/6By (C6By), BALB/cBy (BALB] using an abdominal constriction assay. The analgesic effect of subcutaneously administered morphine and FK33,824 in both beige and CXBK mice was significantly reduced compared with the controls and the analgesic effect of U50,488H and tifluadom in beige mice was significantly reduced compared with the wild strain (C6J). No reduction of analgesic effect of U50,488H and tifluadom was seen in CXBK compared with its progenitor strains, C6By and BALB, except for a reduction of the effect of tifluadom in CXBK compared with C6By. There was no strain difference in the bremazocine-induced analgesia. These results suggest that the beige mouse has a deficit in analgesia mediated by both mu- and kappa-opioid receptors, whereas the CXBK is deficient only in the mu-opioid receptor-mediated analgesia.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Acetates; Acetic Acid; Analgesics; Animals; Benzodiazepines; Benzomorphans; D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; Female; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred Strains; Morphine; Narcotics; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

The role of alpha 2-adrenoceptors and kappa-opioid receptors in urination was studied in rats. In water-loaded rats (40 mL kg-1 p.o.) the kappa-opioid agonist bremazocine (0.05 0.2 mg kg-1 i.p.) induced a dose-related diuretic response in the second hour after administration, but had no effect in the first hour. When rats were pretreated with the alpha 2-adrenoceptor antagonist idazoxan (1 mg kg-1 s.c.), bremazocine induced a dose-related antidiuretic response in the first hour; thereafter the rats showed an increase of urination similar to that with bremazocine alone. The antidiuretic effect of bremazocine was dependent on the dose of idazoxan with maximal response after 1-3 mg kg-1. Similar results were obtained with bremazocine in the presence of yohimbine (1 mg kg-1 s.c.). The antidiuretic profile of bremazocine after idazoxan was shared by U-50,488 (2.5-10 mg kg-1 i.p.), although this compound alone at the high dose reduces urine output in the first hour. The antidiuresis induced by bremazocine in the presence of idazoxan in water-loaded rats was completely antagonized by 10 but not 2 mg kg-1 i.p. of the opioid antagonist naloxone. Thus, kappa-opioid agonists, in addition to their diuretic effect, also produce an antidiuretic response which may be mediated by alpha 2-adrenoceptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenergic alpha-Antagonists; Animals; Benzomorphans; Dioxanes; Diuresis; Dose-Response Relationship, Drug; Idazoxan; Male; Naloxone; Pyrrolidines; Rats; Rats, Inbred Strains; Yohimbine

If different populations of opioid receptors mediate the actions of mu and kappa opioid agonists, then tolerance induced by the chronic administration of a mu agonist should confer cross-tolerance to other mu agonists but not necessarily to those compounds whose effects are mediated by the kappa receptor. This hypothesis was evaluated in the present investigation by examining the effects of the mu agonists morphine, l-methadone and fentanyl, the kappa agonists U50,488 and bremazocine, and the mixed kappa/mu agonist ethylketocyclazocine in rats responding under a fixed-ratio 30 schedule of food presentation before, during and after exposure to a regimen of chronic morphine administration. For comparison, naloxone was evaluated as a representative mu antagonist and the phenothiazine chlorpromazine as a control drug. During all phases of the experiment, each of these compounds produced dose-related decreases in rate of responding. During the daily administration of 40 mg/kg morphine, tolerance developed to the rate-decreasing effects of morphine, l-methadone and fentanyl, and an enhanced sensitivity to the effects of naloxone. In contrast to the effects obtained with these mu opioids, there was no evidence that chronic morphine administration produced tolerance or enhanced sensitivity to the rate-decreasing effects of U50,488, bremazocine, ethylketocyclazocine and chlorpromazine. The present findings demonstrate that the chronic administration of morphine results in the selective development of tolerance to other mu agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Chlorpromazine; Conditioning, Operant; Dose-Response Relationship, Drug; Drug Tolerance; Ethylketocyclazocine; Fentanyl; Food; Male; Methadone; Morphine; Naloxone; Narcotics; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Reinforcement Schedule

Fentanyl, a selective mu opioid receptor agonist, administered intravenously, influences growth hormone secretion in conscious male rats. A dose-response study demonstrated that the maximum growth hormone release was obtained with 10 micrograms/kg while higher doses were less or not effective. MR-2266 (6 mg/kg i.v.), a mu and kappa opioid receptor antagonist, and bremazocine (0.1 mg/kg i.v.) a mu opioid receptor antagonist with kappa agonistic properties, both potently inhibited the growth hormone response to fentanyl (10 micrograms/kg i.v.). In contrast, the effect of fentanyl on growth hormone release was not blocked in rats treated with either ICI-154129 (30 mg/kg i.v. or 150 micrograms/kg intracerebroventricularly a selective delta opioid receptor antagonist, or U-50488 (10 mg/kg i.v.), a specific kappa opioid receptor agonist. These results suggest that opioid receptors of the mu type are involved in the fentanyl-induced growth hormone release.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Dose-Response Relationship, Drug; Enkephalin, Leucine; Fentanyl; Growth Hormone; Male; Narcotic Antagonists; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, mu

The present study was designed to explore the nature of the interaction between mu and kappa opioid agonists in the rat drug discrimination procedure. In rats trained to discriminate the kappa agonist U50,488 (5.6 mg/kg) from water, the other kappa agonist bremazocine substituted completely for the U50,488 training stimulus, and the additional kappa agonist tifluadom substituted in three of five of rats tested. In contrast, the mu agonists morphine, fentanyl, and buprenorphine produced primarily vehicle-appropriate responding. When morphine, fentanyl, and buprenorphine were combined with the training dose of U50,488, all three mu agonists reduced U50,488-appropriate responding. In rats trained to discriminate the mu agonist morphine (10.0 mg/kg) from saline, the other mu agonists morphine and buprenorphine all substituted in a dose-dependent manner for the morphine training stimulus, whereas U50,488, bremazocine, and tifluadom produced primarily vehicle-appropriate responding. When combined with the training dose of morphine, bremazocine antagonized morphine's discriminative stimulus effects, whereas U50,488 and tifluadom had no effect. The barbiturate pentobarbital neither substituted for, nor antagonized, the discriminative stimulus effects of either U50,488 or morphine. These results suggest that mu agonists and kappa agonists produce interacting effects in the drug discrimination procedure in rats.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Buprenorphine; Discrimination, Psychological; Dose-Response Relationship, Drug; Drug Interactions; Fentanyl; Male; Morphine; Pentobarbital; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Binding Sites; Binding, Competitive; Brain; Guinea Pigs; In Vitro Techniques; Kinetics; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa

A series of U50,488 related isothiocyanates was synthesized from enantiomerically pure (S,S)-(+)-trans-2-pyrrolidinyl-N-methylcyclohexylamine [(+)-7] and (R,R)-(-)-trans-2-pyrrolidinyl-N-methylcyclohexylamine [(-)-7]. DCC coupling of (+)- and (-)-7 with nitrophenylacetic acids followed by catalytic hydrogenation and treatment with thiophosgene afforded a series of six isomeric aryl isothiocyanate analogues of U50,488. Similarly, DCC coupling of (+)- and (-)-7 with (+)- and (-)-N-t-Boc-protected phenylglycines afforded four isomeric alkyl isothiocyanates. Evaluation of the isothiocyanates for their capacity to produce wash-resistant inhibition of mu, delta, and kappa sites in vitro was performed using rat and guinea pig brain membranes. None of the compounds was able to irreversibly inhibit binding of [3H]bremazocine to guinea pig and rat brain membranes (depleted of functional mu and delta receptors by pretreatment with acylating agents BIT and FIT). However, (1S,2S)-trans-2-isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(-)-1] was able to specifically and irreversibly inhibit kappa receptors labeled by [3H]-U69,593: Incubation of rat brain membranes for 60 min at 25 degrees C with 1 microM of (-)-1 resulted in a wash-resistant reduction of the binding to 11.2 +/- 2.5% of the control. Binding analysis revealed the wash-resistant reduction in [3H]-U69,593 binding by (-)-1 to be through an increase in the Kd without effect on the Bmax. (-)-1 failed to effect mu or delta binding in rat or guinea pig brain under the same conditions. The enantiomer of (-)-1, (1R,2R)-trans-2-isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(+)-1], failed to affect kappa receptors labeled by [3H]-U69,593 under the same conditions as for (-)-1. (1S,2S)-trans-3-Isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(-)-2] inhibited to 49.6 +/- 5.1% of the control, in a wash-resistant manner, kappa receptors labeled by [3H]-U69,593. However, (-)-2 was not as selective as (-)-1 since it also reduced [3H]DADLE (delta) binding to 82.4 +/- 8.0% of the control value. (1S,2S)-trans-4-Isothiocyanato-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]benzeneacetamide [(-)-3] exhibited selective wash-resistant inhibition of delta receptors labeled by [3H]DADLE resulting in a reduction in binding to 42.9 +/- 4.2% of control.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Binding Sites; Brain; Chemical Phenomena; Chemistry; Cyclohexanes; Guinea Pigs; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Structure-Activity Relationship; Thiocyanates

By using a two-lever drug discrimination task, four groups of rats were trained to discriminate either a low (3.0 mg/kg) and a high (5.6 mg/kg) training dose of the kappa opioid agonist U50,488 [trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolindinyl)cyclohexyl] benzeneacetamine methanesulfonate hydrate] or a low (3.0 mg/kg) and a high (10 mg/kg) training dose of the mu opioid agonist morphine from water. The stimulus effects of the high training dose of U50,488 were shared by the kappa agonists bremazocine and ethylketocyclazocine (i.e., these drugs produced at least 80% drug-appropriate responding), but not by the mu agonists morphine, fentanyl and l-methadone or the nonopioid compounds d-amphetamine, pentobarbital and phencyclidine. Conversely, the stimulus effects of the high training dose of morphine were shared by other mu agonists, but not by the kappa agonists or the nonopioid compounds examined. Similarities in the stimulus effects of morphine and U50,488 occurred, however, when mu and kappa agonists were examined in rats trained to discriminate relatively low training doses of morphine or U50,488 from water. At the low training dose of morphine, complete substitution was obtained with the mu agonists tested as well as the kappa agonist ketocyclazocine. In these rats, intermediate (approximately 70% drug-appropriate responding) levels of substitution were obtained with the kappa agonists bremazocine and ethyylketocyclazocine. Similarly, at the low training dose of U50,488 both the mu and kappa agonists examined substituted completely. Asymmetrical substitution occurred between U50,488 and morphine at the low training doses, with morphine substituting completely for the low training dose of U50,488 and U50,488 failing to substitute for the low training dose of morphine. The rank order of potency for naloxone as an antagonist of the stimulus effects of morphine and U50,488 was; 3.0 mg/kg of morphine greater than 10 mg/kg of morphine greater than 3.0 mg/kg of U50,488 = 5.6 mg/kg of U50,488. The present results indicate that training dose is an important determinant of the different levels of cross-substitution obtained between mu and kappa agonists, and that a greater pharmacological specificity of drug-induced discriminative stimuli can be obtained when relatively high training doses of mu and kappa opioid agonists are used to establish the discrimination.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Cyclazocine; Discrimination Learning; Dose-Response Relationship, Drug; Ethylketocyclazocine; Fentanyl; Male; Methadone; Morphine; Naloxone; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

The modulation of the electrically evoked release of [3H]dopamine (DA) and [14C]acetylcholine (ACh) by opioid receptor activation was examined in superfused slices from rat nucleus accumbens, olfactory tubercle, and frontal cortex. In all brain areas examined, [3H]DA release was inhibited by the kappa agonist, U 50,488 (1-100 nM), and this inhibition was fully antagonized by the selective kappa antagonist, norbinaltorphimine (nor-BNI). In the frontal cortex, the mu agonist, [D-Ala2,MePhe4,Gly-ol5]enkephalin (DAGO, 0.01-1 microM), also inhibited the evoked release of tritium. However, further experiments (including the use of the D2-receptor agonist, LY 171555, and the alpha 2-adrenoceptor agonist, oxymetazoline) suggest strongly that in the frontal cortex DAGO only inhibits the release of [3H]catecholamine from noradrenergic nerve terminals, despite the use of desimipramine to prevent the uptake of [3H]DA into these terminals. [14C]ACh release from both the nucleus accumbens and olfactory tubercle, but not from the frontal cortex, was inhibited by DAGO (0.01-1 microM) and the delta agonist, [D-Pen2,D-Pen5]enkephalin (DPDPE, 0.01-1 microM). These inhibitory effects were antagonized by 0.1 microM naloxone but not by 3 nM nor-BNI. The irreversible delta ligand, fentanyl isothiocyanate (FIT, 1 microM), only antagonized the inhibition caused by DPDPE. The results indicate that the inhibitory effects of opioids on the in vitro release of DA from dopaminergic nerve fibres arising from the substantia nigra and the ventral tegmental area are mediated by presynaptic kappa receptors only. In those regions where ACh release is modulated by opioids, the type of opioid receptor involved may depend on the type of neuron, i.e. interneuron or afferent neuron.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Acetylcholine; Animals; Benzomorphans; Cerebral Cortex; Corpus Striatum; Dopamine; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Ergolines; In Vitro Techniques; Male; Naloxone; Naltrexone; Nucleus Accumbens; Olfactory Bulb; Oxymetazoline; Pyrrolidines; Quinpirole; Rats; Rats, Inbred Strains; Receptors, Opioid; Septal Nuclei

Morphine, given acutely, inhibits oxytocin secretion in adult female rats, but chronic intracerebroventricular infusion for five to six days induces tolerance and dependence in the mechanisms regulating oxytocin secretion. One explanation for tolerance could be that there is a loss of opioid receptors. To test this hypothesis cryostat sections of selected brain regions and the pituitary, from six control and six intracerebroventricular morphine-infused rats, were processed for quantitative in vitro receptor autoradiography. [3H]Etorphine or [3H](-)-bremazocine were used as ligands, and DAGO, DPDPE and U50,488H as selective displacers from mu-, delta-, and kappa-receptors, respectively. Control incubations had naloxone determined specificity. The supraoptic nucleus (site of oxytocin-secreting magnocellular perikarya) contained both mu- and kappa-receptors in control rats (mean +/- S.E.M. binding of mu-selective [3H]etorphine was 91.8 +/- 25.4 fmol/mg of tissue, and of kappa-selective [3H](-)-bremazocine was 130.4 +/- 25.6 fmol/mg). Chronic morphine treatment caused a 83.9% decrease in binding in mu-selective conditions (P less than 0.05), but no significant change in kappa-selective binding. In the median preoptic nucleus (which projects to the supraoptic nucleus) mean +/- S.E.M. binding of [3H]etorphine decreased by 77.0% (P less than 0.01) in chronic morphine-treated rats, from the control value of 76.2 +/- 9.8 fmol/mg of tissue. In the posterior pituitary gland (site of the terminals of the oxytocin-secreting magnocellular perikarya) binding with [3H](-)-bremazocine in controls was over 90% lower than in the supraoptic nucleus. No changes followed chronic morphine treatment. Thus chronic morphine exposure reduces the numbers of available mu-receptors in the supraoptic nucleus, and of opioid receptors in the median preoptic nucleus, perhaps accounting for morphine-tolerance in relation to oxytocin secretion.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Autoradiography; Benzomorphans; Binding, Competitive; Drug Tolerance; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Etorphine; Female; Injections, Intraventricular; Morphine; Pituitary Gland, Posterior; Plasma; Preoptic Area; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Supraoptic Nucleus

The behavioral effects of U50,488 [( trans]-3,4-dichloro-N-methyl-N[2-(1- pyrrolidinyl)cyclohexyl]benzeneacetamide), bremazocine, Mr2266 [(-)-5,9-diethyl-2-(3-furylmethyl)-2'-hydroxy-6,7-benzomorphan] and morphine were compared in squirrel monkeys responding under multiple fixed-ratio fixed-interval (FR FI) schedules of food presentation or stimulus-shock termination. Doses of bremazocine (0.001-0.003 mg/kg), U50,488 (0.03-0.1 mg/kg) and Mr2266 (1.0-3.0 mg/kg) that markedly increased overall rates of FI responding maintained by stimulus-shock termination had little effect on or only decreased overall rates of FI responding maintained by food presentation. Each of the kappa opioids decreased FR responding maintained by either consequence. Morphine (0.03-1.7 mg/kg) only decreased responding under all conditions. Pretreatment with Mr2266 (0.1 mg/kg) produced a 10-fold or more rightward shift in the dose-effect functions for morphine under the two multiple schedules and U50,488 under the multiple schedule of food presentation. A 3-fold higher dose of Mr2266 produced an approximately 10-fold rightward shift in the descending portion of the dose-effect functions for U50,488 and bremazocine under the schedule of stimulus-shock termination but did not appreciably alter their rate-increasing effects. Naltrexone (0.1 mg/kg) antagonized the effects of selected doses of morphine or bremazocine on overall rates of responding under the schedule of stimulus-shock termination. In contrast to its effects in combination with morphine, however, naltrexone (0.1-3.0 mg/kg) did not block alterations in patterns of FI responding produced by bremazocine.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Conditioning, Psychological; Dose-Response Relationship, Drug; Electroshock; Male; Morphinans; Morphine; Naltrexone; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Saimiri

Effects of the opioid agonists morphine, l-methadone, ethylketazocine, U50,488 [trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]benzeneacetamide methanesulfonate hydrate], cyclazocine and bremazocine, and the nonopioid chlorpromazine were determined in pigeons responding under a fixed-ratio 30 schedule of food presentation before, during and after chronic morphine administration. Before chronic morphine administration, all drugs produced dose-dependent decreases in response rates. After daily administration of up to 56 mg/kg of morphine for 7 weeks, dose-effect curves for the mu agonists morphine and l-methadone, as well as the mu/kappa agonist ethylketazocine shifted to the right approximately 1 1/4, 3/4 and 1/2 log units, respectively. In contrast, dose-effect curves for the mixed agonist/antagonists cyclazocine and bremazocine each shifted to the left approximately 3/4 log unit, whereas dose-effect curves for the kappa agonist U50,488 and the nonopioid chlorpromazine did not shift during chronic morphine administration. Dose-effect curves for all drugs except bremazocine returned to their prechronic positions within the period 3 to 8 weeks after termination of chronic morphine administration. The present study demonstrates that repeated administration of morphine produces tolerance to its rate-decreasing effects as well as cross-tolerance selective to other opioids possessing mu agonist properties. The cross-tolerance to ethylketazocine observed in morphine-tolerant pigeons corroborates studies of the discriminative stimulus effects of ethylketazocine in pigeons, suggesting that in this species ethylketazocine possesses predominantly mu agonist properties.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Chlorpromazine; Columbidae; Conditioning, Operant; Cyclazocine; Dose-Response Relationship, Drug; Drug Tolerance; Ethylketocyclazocine; Female; Morphine; Pyrrolidines; Receptors, Opioid

Morphine, levorphanol and D-Ala2, Met enkephalin, but not bremazocine, pentazocine, U-50 488H and U-69 593, were found to inhibit adenylate cyclase activity dose-dependently in bullfrog brain membranes. The inhibition of the enzyme activity was abolished by naloxone. These results suggest that the signalling transduction of mu- and delta-agonists is partially mediated by the adenylate cyclase system coupled with opioid receptors, but that kappa-receptors may not be associated with adenylate cyclase.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adenylyl Cyclase Inhibitors; Animals; Benzeneacetamides; Benzomorphans; Binding, Competitive; Brain; Cell Membrane; Enkephalin, Methionine; Guanosine Triphosphate; Guanylyl Imidodiphosphate; Levorphanol; Morphine; Naloxone; Pentazocine; Pyrrolidines; Rana catesbeiana; Receptors, Opioid; Receptors, Opioid, kappa; Sodium Chloride

De Costa et al. (FEBS Lett. 223, 335; 1987) recently described the synthesis of optically pure enantiomers of (+/-)-trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide (U50,488). In the present study we examined the in vitro opioid receptor selectivity of (-)-(1S,2S)-U50,488, (+)-(1R,2R)-U50,488 and (+/-)-cis-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide (the cis diasteromers of U50,488), as well as their pharmacological activities in rhesus monkeys. Using [3H]5 alpha,7 alpha,8 beta-(-)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro (4,5)dec-8-yl]-phenyl-benzeneacetamide ([3H]U69,593) to label kappa binding sites of guinea pig membranes, the apparent dissociation constants of the enantiomers of U50,488 were 0.89 and 299 nM, for the (S,S) and (R,R) enantiomers, respectively. The (-)-cis and (+)-cis diastereomers had apparent Kds of 167 and 2715 nM, respectively. Binding surface analysis of the interaction of (-)-(1S,2S)-U50,488 with kappa binding sites labeled by [3H]bremazocine resolved two binding sites at which (-)-(1S,2S)-U50,488 had Kds of 30 and 10,485 nM, respectively. The (+/-)-cis, (-)-cis and (+)-cis diastereomers of U50,488 (1 microM) did not inhibit [3H]bremazocine binding. Rhesus monkeys were trained to discriminate ethylketocyclazocine (EKC) and saline. All compounds tested substituted completely for EKC. The order of potency was (-)-(1S,2S)-U50,488 greater than (+/-)-U50,488 greater than (+/-)-cis diastereomer of U50,488 greater than (+)-(1R,2R)-U50,488.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Behavior, Animal; Benzeneacetamides; Benzodiazepines; Benzomorphans; Binding, Competitive; Brain Chemistry; Cyclazocine; Discrimination, Psychological; Ethylketocyclazocine; Female; Guinea Pigs; Macaca mulatta; Male; Membranes; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Stereoisomerism

The effects of kappa-opioid receptor agonists, bremazocine, U-50, 488H and tifluadom and of a mu-opioid receptor agonist, morphine, on food intake and urinary output in food-deprived and nondeprived Sprague-Dawley rats was determined. In food-deprived animals, intraperitoneal administration of bremazocine at 0.1 mg/kg increased food intake but at 1.0 and 10.0 mg/kg doses decreased it. Tifluadom (0.1-10.0 mg/kg) had no effect on food intake. U-50,488H at 1.0 mg/kg increased food intake, whereas 10.0 mg/kg dose decreased the food consumption. In nondeprived rats, the kappa-opioid receptor agonists failed to produce any effect on food consumption. In food-deprived rats, all the three kappa-opioid receptor agonists increased the urinary output at the highest dose (10 mg/kg). In nondeprived rats similar effects as in food-deprived rats were observed except bremazocine increased urinary output at all the doses used. These results with kappa-opioid agonists may be related to either the existence of more than one population of kappa-opioid receptors or their differential actions at the opioid receptor types.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Dose-Response Relationship, Drug; Feeding Behavior; Food Deprivation; Male; Morphine; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa; Time Factors; Urination

Pigeons were trained to discriminate a dose of either 0.01 mg/kg of bremazocine or 0.05 mg/kg of fentanyl from water using a two-key drug discrimination procedure. During tests of substitution, the selective kappa-opioid agonists bremazocine, U50, 488 and tifluadom substituted for the bremazocine stimulus, whereas the less selective kappa-opioid agonists ethylketocyclazocine, levallorphan, proxorphan and nalorphine substituted for the fentanyl stimulus. The full mu-opioid agonists fentanyl, morphine, I-methadone and levorphanol, as well as the partial agonists nalbuphine, butorphanol and buprenorphine, substituted for the fentanyl stimulus. Compounds with partial-opioid agonist effects, namely nalbuphine, butorphanol, buprenorphine, proxorphan, levallorphan and nalorphine, produced 50% fentanyl-appropriate responding at doses 25 to 369.2 times smaller than the doses required to decrease response rates to 50% of control values. In contrast, the full mu-opioid agonists fentanyl, morphine, I-methadone and levorphanol produced 50% fentanyl-appropriate responding at doses only 1.3 to 10.9 times smaller than those required to decrease response rates by 50%. During tests of antagonism, both naloxone and Mr2266 produced a dose-dependent attenuation of the stimulus effects of bremazocine and fentanyl, whereas beta-funaltrexamine antagonized the stimulus effects of fentanyl but not bremazocine. Although bremazocine has been reported to have mu-opioid antagonist effects, it failed to antagonize the stimulus effects of the training dose of fentanyl. The present investigation establishes further that pigeons can discriminate selective kappa-opioid agonists from mu-opioid agonists and that in pigeons the classification of numerous opioid compounds on the basis of their kappa-like or mu-like stimulus effects differ from those in rat and monkey. In addition, under the drug discrimination procedure the actions of compounds classified as partial-opioid agonists can be differentiated from those of full mu-opioid agonists on the basis of the ratio of the dose required to engender fentanyl-like stimulus effects to the dose required to reduce response rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Columbidae; Cyclazocine; Discrimination Learning; Ethylketocyclazocine; Fentanyl; Morphinans; Naloxone; Narcotics; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

The effects of the mu-selective opioid, levorphanol (0.03-1.0 mg/kg), and the kappa-selective opioids, U-50,488 (0.03-1.0 mg/kg), tifluadom (0.01-0.3 mg/kg), bremazocine (0.0003-0.01 mg/kg) and MR 2034 (0.001-0.03 mg/kg), on ventilation and on schedule-controlled behavior were studied in rhesus monkeys. In seated, unanesthetized monkeys prepared with a head plethysmograph, ventilation during exposure to 5% CO2 mixed in air was measured after cumulative doses of each drug. In other monkeys, effects on behavior were studied by administering cumulative doses preceding sequential periods of fixed-ratio responding. Levorphanol, tifluadom, bremazocine and MR 2034 produced dose-related decreases in minute volume, tidal volume and respiratory frequency. In contrast, U-50,488 had only minimal effects on ventilation over the range of doses studied. All drugs decreased fixed-ratio rates in a dose-related manner. Comparisons between their effects in behavioral and respiratory experiments differentiated levorphanol and MR 2034 from U-50,488, bremazocine and tifluadom. Doses of levorphanol or MR 2034 that decreased minute volume markedly had little effect on behavior. In contrast, bremazocine, tifluadom and U-50,488 had less pronounced effects on minute volume at doses that suppressed behavior markedly. Naltrexone (0.03-1.0 mg/kg) antagonized decreases in minute volume produced by levorphanol, MR 2034, bremazocine and tifluadom, and apparent pA2 values were similar for each naltrexone-agonist pair. When the effects of levorphanol (0.03-0.3 mg/kg) were determined in the presence of U-50,488 (0.3 mg/kg), tifluadom (0.1 mg/kg) or bremazocine (0.003 mg/kg), the levorphanol dose-effect curve was shifted approximately 3-fold to the left, suggesting that the effects of the drugs were additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Behavior, Animal; Benzodiazepines; Benzomorphans; Carbon Dioxide; Levorphanol; Macaca mulatta; Male; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Respiration

The effects of mu-agonists (morphine, fentanyl) and kappa-agonists (U-50,488, U-69,593, bremazocine, nalbuphine, tifluadom) on the electroconvulsive threshold were studied in mice. The threshold could be significantly elevated by all drugs tested in a dose range that was in the order of magnitude of the antinociceptive ED50. Mice tolerant to the antielectroshock effect of morphine still reacted to U-69,593. The antagonism of the anticonvulsant effect by the mu-antagonist naloxone and the kappa-antagonist MR 2266 was receptor-specific only with fentanyl and U-50,488. The other opioid agonists were either antagonized by both drugs (morphine, U-69,593, bremazocine, nalbuphine) or even by the opposite antagonist (tifluadom). A synergistic effect of mu- and kappa-stimulation is assumed for the mediation of the antielectroshock effect of opioid drugs, but drugs with high affinity and intrinsic activity at one receptor type (fentanyl, U-50,488) are obviously able to bring about their antielectroshock effect through the one respective opioid binding site.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzeneacetamides; Benzodiazepines; Benzomorphans; Electroshock; Fentanyl; Male; Mice; Morphinans; Morphine; Nalbuphine; Naloxone; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Seizures

The effects of several mu and kappa opioid agonists were examined alone and in combination with the opioid antagonist quadazocine in squirrel monkeys responding under a schedule of shock titration. Under this procedure, shock was scheduled to increase once every 15 sec from 0.01 to 2.0 mA in 30 steps. Five responses on a lever during the 15-sec shock period terminated the shock for 15 sec, after which the shock resumed at the next lower intensity. The intensity below which the monkeys maintained the shock 50% of the time (median shock level) and the rate of responding in the presence of shock were determined under control conditions and after administration of the mu agonists, l-methadone and fentanyl and the kappa agonists, bremazocine, ethylketocyclazocine, ketocyclazocine and U50,488. When examined alone, intermediate doses of mu and kappa agonists increased median shock level. At the highest doses of these compounds responding was eliminated and shock rose to its peak intensity. When the mu and kappa agonists were examined in combination with quadazocine, dose-effect curves for median shock level and for rate of responding were shifted to the right in a dose-dependent fashion. A comparison of the pA2 values for quadazocine on median shock level and on rate of responding revealed similar values for the two measures; however, pA2 values differed depending on the agonist examined. That is, the pA2 values for quadazocine in combination with l-methadone and fentanyl on median shock level were 7.43 and 7.61, respectively; whereas the pA2 value for quadazocine in combination with bremazocine and U50,488 were 6.53 and 6.43, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Animals; Azocines; Benzomorphans; Cyclazocine; Dose-Response Relationship, Drug; Ethylketocyclazocine; Fentanyl; Male; Methadone; Narcotic Antagonists; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Saimiri

Three novel opioid agonists are described. These compounds were found to bind with high affinity and selectivity to the kappa-opioid receptor. Isolated tissue studies using the field-stimulated mouse vas deferens and guinea-pig ileum preparations confirmed the high agonist potency and naloxone-reversibility of these agents. All three compounds exhibited potent antinociceptive activity in the mouse abdominal constriction model. These compounds should prove useful as tools to investigate kappa-receptor function.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Electric Stimulation; Guinea Pigs; In Vitro Techniques; Mice; Morphinans; Muscle Contraction; Muscle, Smooth; Naloxone; Narcotics; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa

The effect of i.p. administration of kappa-opioid receptor agonists, bremazocine, tifluadom and U-50,488H on morphine (8 mg/kg i.p.)-induced analgesia in morphine-naive and morphine tolerant male Sprague-Dawley rats was determined using the tail-flick test. The tolerance to morphine in the rats was induced by s.c., implantation of six morphine pellets during a 7-day period. Implantation of morphine pellets resulted in the development of tolerance as evidenced by the decrease in the analgesic response to morphine when compared to placebo pellets implanted rats. Bremazocine (0.3, 1.0 and 3.0 mg/kg) and U-50,488H (16 mg/kg) antagonized morphine-induced analgesia in morphine-naive rats while tifluadom (8 and 16 mg/kg) potentiated the effect. In morphine-tolerant rats, bremazocine (3 mg/kg) and U-50,488H (16 mg/kg) potentiated morphine-induced analgesia. Tifluadom at any of the doses had no effect on morphine-induced analgesia in morphine-tolerant rats. These results provide evidence that different kappa-opioid agonists modify morphine-induced analgesia differentially in morphine-naive and morphine-tolerant rats.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Dose-Response Relationship, Drug; Drug Synergism; Drug Tolerance; Male; Morphine; Narcotic Antagonists; Pain Measurement; Pyrrolidines; Rats; Rats, Inbred Strains; Tail

The effects of three kappa opioid agonists namely, bremazocine, tifluadom and U-50,488H were studied on blood pressure and heart rate in urethane-anesthetized normal and bilateral adrenal demedullated rats. Bremazocine (0.2, 0.4 and 0.6 mg/kg i.v.) produced a dose-dependent decrease in heart rate, while only 0.4 mg/kg bremazocine produced marked hypotension. The effect appeared to be long lasting because even at 60 min following drug administration the decreases in both heart rate and blood pressure continued. Bilateral adrenal demedullation did not change bremazocine-induced fall in blood pressure but the bradycardia was partially blocked. Tifluadom (0.1-0.4 mg/kg i.v.) produced an initial arrest of heart beat followed by bradycardia which recovered in about 60 min. Except for a very transient fall soon after drug administration no significant effect was observed on blood pressure. In adrenal demedullated rats, tifluadom induced initial arrest of heart was not affected but the subsequent bradycardia was blocked. U-50,488H (0.2, 0.4 and 0.6 mg/kg i.v.) produced dose-dependent bradycardia and hypotension both of which were blocked following bilateral adrenal demedullation. Naltrexone methylbromide (MRZ 2663 BR), a quaternary opioid antagonist, injected 5 min prior to U-50,488H, blocked its cardiovascular effects. The results suggest that kappa opioid agonists given i.v. depress cardiovascular system and these effects are mediated through the adrenal medulla and peripheral opioid receptors. The differential effects of kappa opioid agonists on blood pressure and heart rate suggest that either the three kappa agents interact differentially at the kappa opioid receptors or the subtypes of receptors for the kappa opioid exist.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenal Medulla; Animals; Benzomorphans; Blood Pressure; Cardiovascular System; Dose-Response Relationship, Drug; Heart Rate; Male; Morphinans; Naltrexone; Narcotic Antagonists; Pyrrolidines; Rats; Rats, Inbred Strains; Tape Recording

An observational analysis of the effects of four kappa-opioid agonists on forward locomotion, rearing and grooming displayed by rats in a novel open field was undertaken. The doses of agonists used corresponded to those previously found to produce changes in food consumption. Ethylketocyclazocine (0.1 and 1 mg/kg), bremazocine (0.01 and 0.1 mg/kg) and tifluadom (0.3 and 3 mg/kg) exerted suppressant effects on all the activities monitored. Grooming behaviour appeared to be particularly sensitive to this action, being virtually abolished by the larger doses of these compounds. In contrast, the selective kappa agonist U-50,488H (0.1-3 mg/kg) only attenuated grooming at the two highest doses tested (1 and 3 mg/kg). None of the agonists tested produced stimulation of open field activity during the 1-h study. Reductions in activity occurred at doses previously found to increase and decrease food intake. It was therefore concluded that the hyperphagia induced by kappa agonists was not part of a more general behavioural activation, whilst reductions in food consumption probably result from a non-specific behavioural depression.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Opioid; Animals; Behavior, Animal; Benzodiazepines; Benzomorphans; Cyclazocine; Diuretics; Ethylketocyclazocine; Male; Motor Activity; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Time Factors

The intrathecal injection of a variety of selective kappa-opioid receptor ligands did not result in significant inhibition of thermal nociceptive tail flick responses in rats. In contrast, these compounds dose dependently inhibited pressure nociceptive responses. Cross-tolerance studies revealed that the kappa-opioid receptor ligands tifluadom, U-50488H and dynorphin-(1-17) act upon a receptor distinguishable from the receptor through which morphine exerts its inhibition of mechanical nociceptive responses. The less selective kappa-opiate receptor ligands bremazocine and ethylketocyclazocine (EKC), however, blocked both tail flick and tail pressure nociceptive responses and their effect showed marked cross-tolerance to morphine in the tail flick nociceptive test, but not for the pressure nociceptive responses. We suggest that EKC and bremazocine act upon the spinal kappa-opioid receptor to block mechanical nociceptive responses but that the analgesic effect of EKC and bremazocine on thermal nociceptive responses is probably mediated via spinal micron- and/or delta-, and delta-opioid receptors, respectively.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzodiazepines; Benzomorphans; Cyclazocine; Drug Tolerance; Dynorphins; Ethylketocyclazocine; Injections, Spinal; Male; Morphine; Pyrrolidines; Rats; Rats, Inbred Strains; Reaction Time; Receptors, Opioid; Receptors, Opioid, kappa; Spinal Cord

D-Ala2, D-Leu5-enkephalin (DADLE) and dynorphin1-13 (Dyn1-13) inhibited striatal adenylate cyclase activity, both basal and dopamine-stimulated (DA), in rats and guinea pigs. The kappa-agonists bremazocine (BRZ), U-50,488 (trans-3,4-dicloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide), and U-69,593 (5 alpha, 7 alpha 8 beta)-(-)-N-methyl-N-(7-(1-pyrrolidinyl-1-oxaspiro (4.5)dec-8yl) benzeneacetamide inhibited only the basal adenylate cyclase activity, and such an effect was restricted to guinea pig striatum, an area known to contain a high density of kappa-binding sites. Moreover, BRZ was found to antagonize the inhibitory effect of both DADLE and Dyn1-13 in rat striatum.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adenylyl Cyclases; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Corpus Striatum; Dynorphins; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Enkephalins; Guinea Pigs; Male; Morphinans; Peptide Fragments; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid

The effects of mu, delta and kappa opioid receptor agonists were examined on evoked field potentials in brain slices prepared from rat hippocampus. The effects of the mu-selective opioid peptide [D-Ala2, NMe-Phe4, Met(O)5ol]enkephalin (FK 33-824) and the delta-selective peptide [D-Pen2, D-Pen5]enkephalin (DPDPE) were qualitatively and quantitatively similar. Both increased the amplitude of evoked population spike responses when perfused in low nanomolar concentrations in a fashion consistent with what has been previously reported for other opiate agonists such as morphine. The kappa-selective agonists bremazocine and U-50, 488H were without effect upon evoked responses at concentrations as high as 10 microM. Bremazocine, but not U-50, 488H, proved to be an extremely potent antagonist of responses to both mu- and delta- selective agonists. Moreover, bremazocine was considerably more potent in antagonizing responses to FK 33-824 than DPDPE, which supports the hypothesis that FK 33-824 and DPDPE act via different receptors. Thus, although bremazocine is an agonist at kappa receptors, it appears to act as an antagonist at other opioid receptor sites.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; Electric Stimulation; Electrodes; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Hippocampus; In Vitro Techniques; Male; Morphinans; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu

Marked diuresis has previously been reported after administration of kappa opioid agonists. The present study shows that this effect is stereospecific; MR-2034 markedly increased urinary output over the dose range 0.08 to 1.25 mg/kg, whereas the opposite isomer, MR-2035, was markedly less potent. Bremazocine increased urinary output in Long-Evans hooded and Sprague-Dawley albino rats as well as lean and fatty Zucker rats. In the lean Zucker and the albino rats, bremazocine produced an inverted U-shaped diuretic dose-effect curve, an effect characteristic of kappa agonists with mu agonist activity. This pattern was not seen with the fatty Zucker rats or the Long-Evans hooded rats. The full kappa agonists bremazocine, ethylketazocine and U-50,488 increased urinary output under three different conditions of hydration: water loaded, normal hydration and water deprived. In contrast, the partial kappa agonists reliably only increase urinary output under the normal hydration condition. The diuretic effects of full and partial kappa agonists correlated with plasma vasopressin levels in water-deprived rats. The full kappa agonists (ethylketazocine, U-50,488, tifluadom and MR-2034) suppressed plasma vasopressin levels below the threshold of detectability of the radioimmunoassay, whereas the partial kappa agonists (nalorphine and butorphanol) suppressed vasopressin levels compared with control values but did not have the efficacy of the full kappa agonists. All these results support the hypothesis that kappa agonists produce their diuretic effect by suppression of plasma vasopressin levels.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Butorphanol; Cyclazocine; Diuresis; Drinking; Ethylketocyclazocine; Female; Male; Nalorphine; Pyrrolidines; Rats; Rats, Inbred Strains; Rats, Zucker; Receptors, Opioid; Receptors, Opioid, kappa; Stereoisomerism; Vasopressins; Water Deprivation

In rhesus monkeys, kappa opioid agonists have been shown to increase urinary output, increase tail-withdrawal latencies from warm water and produce distinct discriminative stimulus effects. In order to explore further the relation between these effects and activity at the kappa opioid receptor type, the antagonist activity of quadazocine against several kappa opioid agonists was examined with the tail-withdrawal and drug-discrimination procedures. Quadazocine dose dependently antagonized the increases in tail-withdrawal latency produced by the kappa agonists bremazocine, ethylketazocine and U-50, 488, as well as the discriminative stimulus effects of these drugs. The dose-ratio analysis of Schild revealed apparent pA2 values for quadazocine in combination with bremazocine, ethylketazocine and U-50, 488 of 6.1, 6.4 and 6.4, respectively, with the tail-withdrawal procedure and 6.3, 6.4 and 6.1, respectively, with the drug-discrimination procedure. Quadazocine also antagonized the effects of a mu agonist (morphine) in the tail-withdrawal procedure, and the apparent pA2 value for these data was 8.2. The activity of the mu-selective alkylating agent, beta-funaltrexamine (beta-FNA), was examined alone and in combination with the kappa agonist ethylketazocine in the urinary-output, tail-withdrawal and drug-discrimination procedures. At about 30 to 60 min postinjection, beta-FNA alone produced ethylketazocine-appropriate responding under the drug-discrimination procedure and increased urine output but did not increase tail-withdrawal latencies. At 24 to 48 hr postinjection, beta-FNA did not antagonize effects of ethylketazocine in any of the three procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Azocines; Benzomorphans; Cyclazocine; Diuresis; Endorphins; Ethylketocyclazocine; Female; Hot Temperature; Macaca mulatta; Male; Morphine; Naltrexone; Narcotic Antagonists; Pyrrolidines; Reaction Time; Tail

Intracellular recordings of the CA3 pyramidal neurons in the guinea pig hippocampus were made in vitro. U-50 488H (100 microM), a selective opioid kappa agonist, decreased the synaptic response produced by stimulation of the mossy fibers but did not affect the membrane potential, the input resistance and the generation of the Na+ spikes or the Ca2+ spikes. Iontophoretically applied U-50 488H depressed the depolarization produced by L-glutamate. U-50 488H (100 microM) also depressed the consistent depolarization produced by veratrine (3 X 10(-5) g/ml) and this effect was partially antagonized by naloxone. Moreover, application of U-50 488H led to a disappearance of the anomalous rectification. These results suggest that U-50 488H depresses the synaptic activities of the CA3 pyramidal neurons by inhibiting a subtype of the Na+ channel, "Na+ channel type II" which slowly closes, of the soma and/or the dendrites of the neurons.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Cyclazocine; Ethylketocyclazocine; Glutamates; Guinea Pigs; Hippocampus; In Vitro Techniques; Male; Neurons; Procaine; Pyramidal Tracts; Pyrrolidines; Tetrodotoxin; Veratrine

The effects of several opioid agonists and the opioid antagonist naloxone were examined in rats responding under a fixed-consecutive-number (FCN) schedule. Under this schedule, a reinforced response run consisted of responding eight or more times on one response lever, and then responding once on a second response lever. In one component of this schedule, an external discriminative stimulus signalled the completion of the response requirement on the first lever, whereas no stimulus change was programmed in the other. Morphine, l-methadone, U50488, ketocyclazocine, phencyclidine, and (+/-)N-allylnormetazocine decreased the percent of reinforced response runs (accuracy) under the FCN schedule without the external discriminative stimulus, but had no effect under the FCN schedule with the external discriminative stimulus. Naloxone and bremazocine, in contrast, had no effect on the accuracy of the discrimination under either FCN schedule. With the exception of bremazocine and U50488, which increased rates of responding at low doses, all drugs produced comparable decreases in rates of responding under both FCN schedules. During tests of antagonism, a 0.1 mg/kg dose of naloxone reversed completely the accuracy-decreasing effects produced by U50488 and morphine. The rate-decreasing effects of morphine and U50488 were reversed completely by a 0.01 and 1.0 mg/kg dose of naloxone, respectively. These results suggest that the addition of an external discriminative stimulus can modulate the disruptive effects of opioids, and that mu, sigma and some kappa agonists produce similar effects when evaluated under the FCN schedules.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Conditioning, Operant; Cyclazocine; Discrimination Learning; Ethylketocyclazocine; Male; Methadone; Morphine; Naloxone; Narcotics; Phenazocine; Pyrrolidines; Rats; Reinforcement Schedule

We investigated the effects of dynorphin A (Dyn A), a heptadecapeptide, on the population spikes of the guinea pig hippocampal CA3 pyramidal neurons, in vitro, using paired-pulse stimulation of the mossy fibers. Dyn A produced facilitatory and inhibitory effects on the population spikes in the preparations with lower and higher degrees of paired-pulse facilitation, respectively. Morphine and D-Ala2, D-Leu5-en-kephalin, mu- and delta-agonist, respectively, predominantly potentiated the population spikes, while kappa-agonists such as U-50, 488H and bremazocine mainly caused an inhibition. These results suggest that Dyn A has two separate (excitatory and inhibitory) effects on the guinea pig hippocampal CA3 neurons through mu-(delta) and kappa-opioid receptors, respectively.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Drug Interactions; Dynorphins; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Guinea Pigs; Hippocampus; In Vitro Techniques; Male; Morphine; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Synaptic Transmission

The effects of bremazocine and U-50,488, two selective opioid kappa receptor agonists, and the preferential mu receptor agonist morphine on the secretion of PRL and GH were compared in conscious male rats bearing permanent right atrial cannulae for serial blood sampling and drug delivery. All three opioids stimulated PRL secretion in a dose-related manner, but the kappa agonists differed from morphine in several respects. They were considerably more potent than morphine in triggering a PRL response, but were unable to elevate PRL levels to more than 100 ng/ml, whereas morphine, at the highest dose (4.5 mg/kg), induced an almost twice larger response. Also their PRL-releasing effect was inhibited more strongly by the preferential kappa receptor antagonist Mr-2266 than by naloxone, whereas Mr-2266 and naloxone, which are equipotent as antagonists of the mu receptors, were equipotent in suppressing the PRL-stimulating effect of morphine, a mu agonist. In a complete contrast to morphine, which effectively stimulated GH secretion, the kappa agonists had no effect on GH release at lower doses and suppressed it at higher doses. It is concluded that the PRL-releasing effect of the kappa agonists is mediated by the kappa receptors which may participate with the mu receptors in regulation of PRL secretion by opioids. The GH-inhibiting effect of the kappa agonists requires further clarification.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Dose-Response Relationship, Drug; Growth Hormone; Injections, Intravenous; Male; Morphinans; Morphine; Naloxone; Prolactin; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa; Time Factors

An analysis of the GH release-inhibiting action of the opioid kappa receptor agonists bremazocine and U-50,488, established earlier, was attempted by testing the agonists against activation of GH secretion by morphine or clonidine in male rats bearing right atrial cannulae for serial blood sampling and drug delivery. Both kappa agonists inhibited the effect of subsequent administration of clonidine in a dose-related manner. Bremazocine was approximately ten times more potent than U-50,488, a ratio corresponding to the known affinities of the two compounds for the kappa receptors. The inhibiting action of bremazocine was more strongly reversed by the preferential kappa receptor antagonist Mr-2266 than by naloxone, neither of which interfered with the GH-stimulating effect of clonidine. Bremazocine, however, did not alter the activation of GH secretion by exogenous growth hormone releasing factor. Thus, the inhibiting effect of bremazocine and probably U-50,488 seems to be derived from stimulation of the kappa receptors which in turn activates a GH release inhibiting mechanism of unknown identify which, however, does not involve release of somatostatin. Both kappa agonists also inhibited the effect of morphine, but in this case U-50,488 was approximately hundred times less effective than bremazocine. Since bremazocine and U-50,488 are antagonists of the delta receptors, which seem to mediate the GH-releasing effect to morphine, their inhibiting effect in this instance may be related to this property rather than to an action on the kappa receptors. Bremazocine, but not U-50,488, was also highly effective in inhibiting stimulation of PRL secretion by morphine.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Clonidine; Growth Hormone; Injections, Intravenous; Male; Morphinans; Morphine; Prolactin; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa; Serotonin; Time Factors

[3H]Bremazocine, in the presence of saturating concentrations of mu and delta receptor blocking agents, was used to label putative kappa opiate binding sites in rat brain. The binding of [3H]bremazocine under these conditions was completely displaced with high affinity by U-50488H and dynorphin1-17, and the potency of a series of opiate ligands was consistent with an action at kappa receptors. Therefore, [3H]bremazocine, in the presence of mu and delta blockers, was used to localize U-50488H-displaceable kappa binding sites by autoradiography. A distribution different from that of mu and delta receptors was seen, with levels highest in the claustrum, striatum, medial preoptic area, suprachiasmatic nucleus, medial amygdala and superior layer of the superior colliculus. The results show that the U-50488H-displaceable kappa sites have a distinct distribution which is discussed in terms of the possible functional roles of kappa receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Autoradiography; Benzomorphans; Binding Sites; Binding, Competitive; Brain; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Enkephalins; Male; Morphinans; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa

Rabbit and guinea-pig cerebellum membrane preparations contain a high proportion (greater than 80%) of mu- and of kappa-opioid binding sites, respectively. These preparations were therefore used to compare the regulation of binding of mu- and of kappa-opioid agonists and antagonists by sodium ions and by guanyl-5'-yl imidodiphosphate. We report here that Na+ ions, Gpp(NH)p and most efficiently, the two agents in association selectively inhibited binding of opioid agonists not only in the mu preparation (rabbit cerebellum) but also in the kappa preparation (guinea-pig cerebellum). These allosteric effectors did not inhibit equilibrium binding of antagonists (naloxone, Mr 2266 or diprenorphine) in the two preparations. Taken together these results suggest that occupancy either of the mu-receptor by a mu-agonist or of the kappa-receptor by a kappa-agonist may be accompanied by similar if not identical molecular events. They also suggest a method to rapidly screen newly designed drugs as mu- or kappa-opioid agonists or antagonists.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Opioid; Animals; Benzomorphans; Binding, Competitive; Cerebellum; Diprenorphine; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Etorphine; Guanosine Triphosphate; Guanylyl Imidodiphosphate; Guinea Pigs; Hydrogen-Ion Concentration; In Vitro Techniques; Naloxone; Pyrrolidines; Rabbits; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Sodium

The proposed kappa opioid receptor agonists ethylketocyclazocine (EK), nalorphine, bremazocine and U-50,488H were evaluated for their ability to produce contractions of isolated, vascularly perfused canine small intestinal segments. Responses to these agonists were compared to those of morphine and phenazocine, a mu benzomorphan. Morphine (0.04-25 micrograms) and phenazocine (0.01-3.0 micrograms) both produced naloxone-reversible contractions, suggesting that the responses were mediated largely by mu opioid receptors. In contrast, the proposed kappa agonists were ineffective in producing intestinal stimulation, with only EK (1-100 micrograms) showing minimal but significant activity at very high doses. We suggest that the effects of EK may be mediated through mu opioid receptors and that kappa receptors appear not to be involved in the contractile response of the dog small intestine to opioids.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzomorphans; Cyclazocine; Dimethylphenylpiperazinium Iodide; Dogs; Ethylketocyclazocine; Gastrointestinal Motility; In Vitro Techniques; Intestine, Small; Morphine; Nalorphine; Phenazocine; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

The purpose of this study was to investigate further the kappa opioid receptor selectivity of the field-stimulated isolated rabbit vas deferens preparation and to study the profile of a series of kappa agonists in this tissue. Agonists acting at mu, delta and sigma receptors were without detectable effect in the rabbit vas deferens. But a number of kappa agonists, including bremazocine, tifluadom, ethylketocyclazocine, ketocyclazocine, U-50,488 and Win 42,610 all depressed contractions, producing parallel dose-response curves. Mr 2034 generally produced a shallower dose-response curve and achieved a lower maximum effect, thus acting like a partial agonist. The effect of ethylketocyclazocine was not reduced by the irreversible mu antagonist, beta-funaltrexamine, confirming that it is not acting via mu receptors. Another group of drugs, including nalorphine, butorphanol and proxorphan, which produce an agonist action via kappa receptors in the guinea-pig ileum and mouse vas deferens, were antagonists in the rabbit vas deferens, suggesting that this tissue will only respond to high efficacy kappa agonists.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzodiazepines; Benzomorphans; Butorphanol; Cyclazocine; Ethylketocyclazocine; In Vitro Techniques; Male; Muscle Contraction; Muscle, Smooth; Nalorphine; Naloxone; Pyrrolidines; Rabbits; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Vas Deferens

The effect of several mu and kappa opioid receptor agonists on rat plasma corticosterone levels, measured using radioimmunoassay, was investigated. The mu agonists, morphine and fentanyl, and the kappa agonists, U-50,488, tifluadom and bremazocine, all produced dose-related increases in rat plasma corticosterone levels. The effects of both fentanyl and U-50,488 were reversed by naloxone, indicating an action at opioid receptors. Pretreatment of the rats with the irreversible, mu-selective antagonist, beta-funaltrexamine, reduced the effect of fentanyl, but not that of U-50,488, indicating that both mu and kappa opioid receptors are involved in mediating this effect.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Corticosterone; Dose-Response Relationship, Drug; Fentanyl; Male; Morphine; Naloxone; Naltrexone; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

Tifluadom (0.625-10.0 mg kg-1) was administered to non-deprived male rats which had been accustomed to eating a highly palatable diet in a 30 min test period. This compound, an opioid benzodiazepine, produced a significant increase in consumption of food when administered by the subcutaneous route, but not after intraperitoneal injection. Both chlordiazepoxide (1.25-20.0 mg kg-1) and the selective kappa opiate receptor agonist U-50,488 (0.3125-2.5 mg kg-1) also produced significant hyperphagic effects in the same feeding situation. In contrast, the two kappa opiate receptor agonists, ethylketocyclazocine (0.1-3.0 mg kg-1) and bremazocine (0.078-1.25 mg kg-1) brought about a dose-related suppression of food intake. Hence, the effects of kappa opiate receptor agonists in the feeding situation described here were not uniform. Furthermore, tifluadom could be likened either to a benzodiazepine or to a selective kappa receptor agonist. The hyperphagia induced by tifluadom was antagonized by naloxone, suggesting that the effect was mediated by an action at opiate receptors. It was not antagonized however by Ro15-1788 (10.0 and 20.0 mg kg-1), a selective benzodiazepine receptor antagonist, ruling out possible mediation by benzodiazepine receptors. The benzodiazepine receptor antagonist, CGS 8216, exhibited intrinsic activity when administered alone, and significantly reduced food consumption in tifluadom-treated and control animals.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzodiazepinones; Benzomorphans; Chlordiazepoxide; Convulsants; Cyclazocine; Drug Interactions; Eating; Ethylketocyclazocine; Flumazenil; Male; Naloxone; Pyrazoles; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa

There is increasing evidence to suggest that kappa opiate receptors may be importantly involved in the mediation of feeding responses in the rat. A series of experiments is reported in which the effects of four kappa receptor agonists (ethylketocyclazocine, U-50,488H, tifluadom, bremazocine) on the consumption of a highly palatable diet were investigated. Under one condition, non-deprived male rats were administered drug treatments before a 30 min feeding test. Bremazocine (0.1 mg/kg) and ethylketocyclazocine (3.0 mg/kg) both significantly decreased the level of food consumption. In contrast, U-50,488H and tifluadom each produced significant increases in food intake. In a second condition, non-deprived male rats were first allowed to consume some of the palatable diet to achieve partial satiation, prior to the administration of the drug treatments. In this case, evidence for hyperphagic effects of all four kappa agonists was obtained, within the first 30 min access to the palatable diet. Thus, hyperphagia occurred with 0.01 mg/kg bremazocine and 0.1 mg/kg ethylketocyclazocine. We conclude that some kappa agonists have mixed stimulant/inhibitory effects on food intake, whereas others are more consistent in producing hyperphagia. In neither condition did morphine (0.3-10.0 mg/kg) show any hyperphagic effect. Our data support an involvement of kappa opiate receptors in mechanisms which control palatable food consumption in non-deprived rats.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Cyclazocine; Eating; Ethylketocyclazocine; Male; Morphine; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Satiety Response

Several opioid antagonists have previously been shown to decrease drinking. The data have suggested that this was due to an antagonist action at kappa opioid receptors rather than mu or delta opioid receptors. Kappa agonists have a marked diuretic effect through suppression of vasopressin release. Antagonism of this kappa receptor-mediated effect can be used as an in vivo test for determining kappa-receptor antagonist activity. The potencies of opioid antagonists for antagonizing the diuretic effects of the kappa agonist bremazocine do not correlate directly with the potencies for decreasing deprivation-induced drinking. Further work should investigate the receptor specificity for effects on drinking and kappa-mediated diuresis.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzodiazepines; Benzomorphans; Butorphanol; Clonidine; Cyclazocine; Drinking; Ethylketocyclazocine; Naloxone; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa; Urination; Vasopressins

The three endogenous opioid precursors of almost 30000 Da are pro-opiocortin, proenkephalin and prodynorphin. Pro-opiocortin contains beta-endorphin, melanotropins and ACTH. Proenkephalin yields one [Leu5]enkephalin, three [Met5]enkephalins, one [Met5] enkephalyl-Arg-Arg-Val-NH2 (metorphamide or adrenorphin), one [Met5]enkephalyl-Arg-Gly-Leu and one [Met5]enkephalyl-Arg-Phe. [Leu5]enkephalin is common to all fragments of prodynorphin; its carboxyl extension by Arg-Lys leads to alpha- and beta-neo-endorphin and its carboxyl extension by Arg-Arg gives two dynorphins A and B of 17 and 13 amino acids, respectively. Another endogenous peptide is dynorphin A (1-8). The three main opioid binding sites are mu, delta and kappa. Their analysis has been facilitated by the synthesis of analogues of peptides and non-peptide compounds, which have selective agonist or antagonist action at only one site. The various physiological roles of the three types of the opiate receptor have so far not been sufficiently investigated.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Binding Sites; Brain; Cyclazocine; Diprenorphine; Enkephalin, Leucine; Enkephalins; Ethylketocyclazocine; Guinea Pigs; Ileum; In Vitro Techniques; Male; Mice; Muscle Contraction; Muscle, Smooth; Myenteric Plexus; Naloxone; Pro-Opiomelanocortin; Protein Precursors; Pyrrolidines; Radioligand Assay; Rats; Receptors, Opioid; Vas Deferens

Several 'so-called' kappa-opiate receptor agonists e.g., ketocyclazocine (Kc), ethylketocyclazocine (Ekc), bremazocine, MR-2034 and U-50488H, were tested on basilar and middle cerebral arteries of the dog in vitro for relaxant or contractile activities. Ekc, Kc and bremazocine were found to produce concentration-dependent reductions in basal tone and to relax cerebral arteries contracted with prostaglandin F2 alpha (PGF2 alpha). All three agonists appear to act on benzomorphan-kappa opiate receptors which subserve relaxation in cerebral blood vessels. MR-2034 and U-50488H were found to induce contraction in the cerebral arteries. These opiate agonists appear to act on phencyclidine (PCP) or sigma-opiate receptors which subserve contraction. A variety of pharmacological antagonists (phentolamine, propranolol, methysergide, atropine, diphenhydramine, cimetidine, naloxone) did not modify any of the cerebral vascular effects produced by the opiates. These results suggest: (1) specific benzomorphan-kappa opiate receptors which subserve relaxation exist in cerebral blood vessels; (2) some kappa agonists appear to produce, primarily, contraction in cerebral vessels via PCP or sigma-opiate receptors: and cerebral vascular muscle may provide a useful tool to analyse the molecular constitution of these two distinct and opposite-acting opiate receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Cerebral Arteries; Cyclazocine; Dinoprost; Dogs; Drug Interactions; Ethylketocyclazocine; Female; In Vitro Techniques; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Phencyclidine; Prostaglandins F; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa

The effects of various opioid agonists and antagonists on urination were studied in the normally hydrated rat. Two kappa agonists, U-50,488H and proxorphan, markedly increased urination. The increased urination produced by U-50,488H was antagonized by opioid antagonists in a potency order which indicated that the effects were due to an action at kappa opioid receptors. Mu agonists decreased urination and were blocked by low doses (0.01 and 0.1 mg/kg) of naloxone, whereas kappa agonists increased urination and were only blocked by a high dose (10 mg/kg) of naloxone. The diuretic effects of U-50,488H and ketazocine, but not proxorphan and bremazocine, were reduced by morphine, consistent with the idea that proxorphan and bremazocine have morphine antagonist activity. Water deprivation produced a shift to the right for the dose-effect curve for bremazocine-induced diuresis. Kappa agonists were ineffective in increasing urination in Brattleboro rats that were homozygous for diabetes insipidus, whereas mu agonists were still effective in decreasing urination. The data are consistent with the hypothesis that kappa agonists inhibit release of vasopressin from the neurohypophysis and this decrease in vasopressin release leads to increased urination. The effects of opioids on urination in the normally hydrated rat can be extremely useful in classifying the activities of opioid on mu and kappa receptors in vivo.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzomorphans; Cyclazocine; Diuresis; Ethylketocyclazocine; Male; Morphinans; Naloxone; Narcotic Antagonists; Narcotics; Piperidines; Pyrrolidines; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Urination

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