u-50488 and naloxone-benzoylhydrazone

Zolpidem and zopiclone are two of a newer hypno-sedative class of drugs, the "Z compounds". Their use for the treatment of short-term insomnia has been expanding constantly during the last two decades. The "Z compounds" are considered to cause less significant rebound insomnia or tolerance than the conventional hypnotic benzodiazepines. Their possible antinociceptive effect and interaction with the opioid system has not been studied yet. Our results demonstrate a significant difference between the antinociceptive properties of zopiclone and zolpidem when injected s.c. in the hotplate analgesic assay in mice. Zopiclone induced a weak, dose-dependent antinociceptive effect, antagonized only by the alpha2-adrenergic receptor antagonist yohimbine. Zolpidem induced a weak, biphasic dose-dependent antinociceptive effect, antagonized primarily by the non-selective opioid antagonist naloxone and by yohimbine. The weak antinociceptive effect of both drugs, evident only at very high doses (far beyond those used clinically to induce sleep), implies no clinical use for zopiclone or zolpidem in the management of pain. However, the possible interaction of zolpidem with the opioid system should be further investigated (in behavioral models, which do not overlap with the acute-pain antinociception model we used), both for possible side effects in special populations (i.e. elderly) and for possible drug-drug interactions, in order to minimize possible hazards and maximize clinical beneficial effects of its use for sleep.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenergic Agonists; Adrenergic Antagonists; Analgesics; Animals; Azabicyclo Compounds; Behavior, Animal; Benzamides; Clonidine; Dose-Response Relationship, Drug; Hypnotics and Sedatives; Male; Mice; Mice, Inbred ICR; Morphine; Naloxone; Narcotic Antagonists; Pain; Pain Measurement; Piperazines; Pyridines; Receptors, Opioid; Serotonin; Serotonin Antagonists; Serotonin Receptor Agonists; Zolpidem

Dopamine systems are intimately involved with opioid actions. Pharmacological studies suggest an important modulatory effect of dopamine and its receptors on opioid analgesia. We have now examined these interactions in a knock-out model in which the dopamine(2) (D(2)) receptor has been disrupted. Loss of D(2) receptors enhances, in a dose-dependent manner, the analgesic actions of the mu analgesic morphine, the kappa(1) agonist U50,488H and the kappa(3) analgesic naloxone benzoylhydrazone. The responses to the delta opioid analgesic [d-Pen(2),d-Pen(5)]enkephalin were unaffected in the knock-out animals. Loss of D(2) receptors also potentiated spinal orphanin FQ/nociceptin analgesia. Antisense studies using a probe targeting the D(2) receptor revealed results similar to those observed in the knock-out model. The modulatory actions of D(2) receptors were independent of final sigma receptor systems because the final sigma agonist (+)-pentazocine lowered opioid analgesia in all mice, including the D(2) knock-out group. Thus, dopamine D(2) receptors represent an additional, significant modulatory system that inhibits analgesic responses to mu and kappa opioids.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Analgesics, Opioid; Animals; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Dose-Response Relationship, Drug; Drug Synergism; Enkephalin, D-Penicillamine (2,5)-; Heterozygote; Mice; Mice, Knockout; Morphine; Naloxone; Nociceptin; Oligonucleotides, Antisense; Opioid Peptides; Pain Measurement; Pentazocine; Receptors, Dopamine D2; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Receptors, sigma; Sulpiride

Buprenorphine is a mixed opioid agonist/antagonist analgesic. This study was designed to determine the role of opioid receptor subtypes, especially kappa 3, in buprenorphine-induced analgesia in mice. Buprenorphine, when injected systemically, revealed a potent analgesic effect by tailflick assay, with a biphasic dose-response curve, which was reversed by naloxone. The presence of analgesic cross-tolerance between buprenorphine and naloxone benzoylhydrazone (NalBzoH) and morphine indicated a role for kappa 3 and mu receptor subtype in buprenorphine analgesia. Additional studies with selective opioid antagonists indicated kappa 1 mechanisms of action. We did not detect any involvement of the delta receptor subtype. Low doses of buprenorphine antagonized morphine analgesia, while high doses of buprenorphine coadministered with morphine elicited increasing analgesia in a dose-dependent manner. These findings suggest that buprenorphine elicits analgesia through an interaction with kappa 3 receptors and to a lesser extent with kappa 1 as well as its activity as partial mu receptor agonist.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Opioid; Animals; Buprenorphine; Drug Interactions; Drug Tolerance; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Male; Mice; Mice, Inbred ICR; Morphine; Naloxone; Narcotic Antagonists; Pyrrolidines; Receptors, Opioid, delta; Receptors, Opioid, kappa; Sensitivity and Specificity

Delta and kappa opioid receptors have been differentiated into further subtypes based upon both biochemical and pharmacological analgesic assays. Whereas hyperphagia elicited by the kappa1 receptor agonist, U50488H is blocked by general and kappa1 opioid antagonists, hyperphagia elicited by the kappa3 receptor agonist, naloxone benzoylhydrazone (NalBzOH) is blocked by general, but not kappa1 opioid antagonists. The first study assessed the opioid antagonist profile of hyperphagia elicited by centrally administered delta1 ([D-Pen2, D-Pen5]-enkephalin, DPDPE: 5-50 microg) and delta2 ([D-Ala2, Glu4]-Deltorphin, Delt II: 5-50 microg) agonists following central pretreatment with general (naltrexone), delta1 ([D-Ala2, Leu5, Cys6]-enkephalin, DALCE) and delta2 (naltrindole isothiocyanate, NTII) opioid antagonists. It is also important to determine whether selective opioid receptor subtype agonists are capable of altering intake in ingestive situations other than spontaneous feeding. The second study examined whether centrally administered delta1, delta2, kappa1 or kappa3 agonists altered the pattern and magnitude of hyperphagia elicited by 2-deoxy-D-glucose (2DG: 50-400 mg/kg, IP). DPDPE-induced hyperphagia was significantly reduced by naltrexone and NTII, but not DALCE. Delt II-induced hyperphagia was significantly reduced by DALCE and NTII, but not naltrexone. Pairing Delt II (5 microg) with low (100-200 mg/kg) 2DG doses significantly enhanced intake, producing a leftward (3-fold) shift in 2DG's hyperphagic dose-response curve. In contrast, DPDPE failed to alter 2DG-induced hyperphagia, and kappa1 and kappa3 opioid agonists each produced small, but significant increases in 2DG-induced hyperphagia. The antagonist data suggest the possibility of physiological and pharmacological interactions between delta receptor subtypes in mediating food intake, and it would appear that delta2 opioid receptors exert facilitatory effects upon glucoprivic hyperphagia.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Cerebral Ventricles; Deoxyglucose; Dose-Response Relationship, Drug; Drug Synergism; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Hyperphagia; Infusions, Parenteral; Male; Naloxone; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Receptors, Opioid, kappa; Regression Analysis

Naloxone benzoylhydrazone (NalBzoH) is a selective, short-acting agonist at the kappa 3 opioid receptor and a slowly dissociating potent antagonist at the mu opioid receptor. Given the important role of kappa receptors in the opioid control of food intake, the present study examined the central and peripheral effects of NalBzoH upon food intake. Central administration of NalBzoH (1-20 micrograms, i.c.v.) significantly increased food intake for up to 12 h, but failed to alter intake or body weight after 24 or 48 h. The 12 h duration of NalBzoH-mediated effects may be due to either persistent kappa 3 receptor occupancy, and/or activation of an ingestive system which maintains its activity. Peripheral administration of NalBzoH (20 mg/kg, s.c.) significantly increased food intake for up to 1 h. To distinguish kappa 1 (U50,488H) and kappa 3 (NalBzoH) hyperphagic effects, these agonist effects were compared following pretreatment with either naltrexone or the kappa 1 antagonist, nor-binaltorphamine (Nor-BNI). Whereas naltrexone significantly reduced both U50,488H and NalBzoH hyperphagia, Nor-BNI blocked U50,448H, but not NalBzoH hyperphagia. These data indicate a distinct role for the kappa 3 receptor in ingestive behavior separable from that of kappa 1 effects.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Cerebral Ventricles; Dose-Response Relationship, Drug; Feeding Behavior; Infusions, Parenteral; Male; Naloxone; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid, kappa; Reference Values

Studies of various strains of mice revealed marked differences in their analgesic sensitivity towards morphine (mu), U50,488H (kappa 1) and naloxone benzoylhydrazone (NalBzoH; kappa 3). Sensitivity to mu and kappa analgesia varied independently of the other. Analgesic sensitivity to morphine remained relatively consistent among 3 different nociceptive assays for each strain. However, the sensitivity of an individual strain to NalBzoH remained highly dependent upon the assay used. CD-1 mice were sensitive to NalBzoH in all 3 assays, but in BALB/c mice NalBzoH produced analgesia only in the hot plate and cold water tail-flick assays. In Swiss-Webster mice, NalBzoH was active in the radiant heat and cold water tail-flicks but inactive in the hot plate. Although the levels of mu, kappa 1 and kappa 3 binding in whole brain homogenates did vary somewhat, they did not correlate with analgesic sensitivity. These results suggests that the genetic controls over mu and kappa analgesia operate independently and further illustrate the many difficulties in evaluating potential analgesics.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Analgesics; Animals; Benzeneacetamides; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Male; Mice; Mice, Inbred Strains; Morphine; Naloxone; Pain; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Species Specificity

In standard 3H-opioid binding assays, the benzoylhydrazone derivative of naloxone (6-desoxy-6-benzoylhydrazido-N-allyl-14-hydroxydihydronormorphi none; NalBzoH) inhibited mu, kappa, and delta binding at nanomolar concentrations. At concentrations as low as 1 nM, it also produced a wash-resistant inhibition of opioid binding. [3H]NalBzoH binding typically gave a ratio of total to nonspecific binding of 8:1. Binding reached steady state levels by 1 hr and was linear with tissue concentration. [3H]NalBzoH labeled two classes of sites. The binding to one was easily reversible whereas the other was not and was termed pseudoirreversible. At 25 degrees, almost 90% of [3H]naloxone binding and approximately 60-75% of [3H]NalBzoH binding dissociated over 90 min. However, the remainder of [3H]NalBzoH binding, corresponding to pseudoirreversible binding, remained constant over the next 5 hr at 25 degrees and additional studies suggested a dissociation half-life of approximately 24 hr. Competition studies indicated that the reversible binding corresponded to neither mu nor delta binding and may represent a novel subtype of kappa receptor. Pseudoirreversible binding was predominantly to a combination of both mu 1 and mu 2 receptors. Despite its extremely slow rate of dissociation, pseudoirreversible binding was not covalent inasmuch as lowering the pH to 5 or adding the GTP analog 5'-guanylylimidodiphosphate [Gpp(NH)p] completely dissociated prebound [3H] NalBzoH. The ability of Gpp(NH)p to dissociate pseudoirreversible [3H]NalBzoH binding raised the possibility that the slow rate of dissociation was related to interactions with a guanine nucleotide-binding protein.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Brain; Cattle; Guanylyl Imidodiphosphate; In Vitro Techniques; Kinetics; Naloxone; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu; Tritium

Kappa receptor multiplicity is a complex area. We now present evidence from binding studies suggesting the existence of four kappa receptor subtypes. The guinea pig cerebellum contains high levels of U50,488-sensitive, or kappa 1, receptors. Kappa opiates (U50,488, tifluadom, Mr2034, Mr2266 and Win44,441) compete [3H]ethylketocyclazocine binding to kappa 1 receptors with kappa, values under 10 nM and Hill coefficients of approximately one, as does dynorphin A (kappa 1, 0.27 +/- 0.05 nM; Hill coefficient, 0.83 +/- 0.20, n = 4). However, competition studies with dynorphin B yield a Hill coefficient of 0.46 +/- 0.03 (n = 5) and nonlinear regression analysis of the competition curve is best fit by two sites. alpha-Neoendorphin Neoendorphin competition curves (Hill coefficient, 0.46 +/- 0.07; n = 3) also were best fit with two components. Competition studies with both alpha-neoendorphin and dynorphin B together suggest that both compounds label the same site with high affinity. Similar results were obtained using [3H]U69,593. Dynorphin B and alpha-neoendorphin competed binding with Hill coefficients of 0.45 +/- 0.04 (n = 3) and 0.59 +/- 0.09 (n = 3), respectively. These data suggest two subtypes of kappa 1 receptors in the guinea pig cerebellum: kappa 1a and kappa 1b. Classical kappa opiates and dynorphin A have high affinity for both subtypes whereas dynorphin B and alpha-neoendorphin label kappa 1b over 50-fold more potently than kappa 1a sites. [3H]Naloxone benzoylhydrazone [( 3H]NalBzoH) labels a novel, U50,488-insensitive kappa receptor subtype, kappa 3, in membranes from calf striatum, rat and mouse brain. We now have developed a relatively selective assay in calf striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Binding Sites; Cattle; Cerebellum; Cyclazocine; Edetic Acid; Ethylketocyclazocine; Guinea Pigs; In Vitro Techniques; Naloxone; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu

NalBzoH (6-desoxy-6-benzoylhydrazido-N-allyl-14-hydroxydihydronomorphin one) is a novel opiate with potent actions at both mu and kappa receptors. Analgesic studies in mice examining increasing doses of NalBzoH with a fixed dose of morphine revealed a biphasic curve. NalBzoH at doses as low as 1 microgram/kg partially antagonized morphine analgesia. Higher NalBzoH doses continued to inhibit morphine analgesia in a dose-dependent manner, with the 1-mg/kg dose antagonizing completely morphine analgesia. As the NalBzoH dose increased beyond 1 mg/kg analgesia returned. NalBzoH also prduced a similar analgesic response when administered alone in mice and also was active in rats. NalBzoH had excellent p.o. activity, with an analgesic potency in mice equivalent to s.c. administration. Naloxone reversed NalBzoH analgesia far less effectively than morphine analgesia. In contrast, Win44,441 antagonized both morphine and NalBzoH analgesia with a similar potency, consistent with a kappa mechanism for NalBzoH analgesia. Repeated administration of NalBzoH resulted in tolerance. There was no analgesic cross-tolerance between NalBzoH and either morphine or the kappa 1-selective agent U50,488H, implying a selective kappa 3 mechanism of analgesia. In addition to blocking morphine analgesia, low doses of NalBzoH also partially reversed the inhibition of gastrointestinal transit in mice produced by morphine, antagonized completely morphine lethality and precipitated withdrawal in morphine-dependent mice, confirming its antagonist activity in mu receptors. The duration of NalBzoH's kappa and mu actions differed dramatically. In mice, analgesia typically lasted less than 2 hr whereas the same NalBzoH dose antagonized completely morphine analgesia, a mu action, for 16 hr. Full sensitivity to morphine did not return for 32 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Animals; Drug Tolerance; Gastrointestinal Motility; Male; Mice; Morphine; Naloxone; Narcotic Antagonists; Pyrrolidines; Receptors, Opioid; Receptors, Opioid, kappa; Receptors, Opioid, mu