Agonist activity of naloxone benzoylhydrazone at recombinant and native opioid receptors (original) (raw)
Related papers
European Journal of Pharmacology, 1991
The fi-adrenoceptor-sensitive adenylate cyclase in primary cultures of rat striatd neurons was inhibited by opioids, unlike that in rat striatal slices. Isoprenaline (1 PM)-stimulated cyclic AMP production was dose dependently inhibited by the p-opioid receptor agonist, [D-AlaZ,MePhe4,Gly-o15]enkephalin (DAGO, EC,, = 0.02 PM, 36% inhibition), and only slightly reduced by relatively high concentrations of the d-opioid receptor agonist, [D-penicillamine2,D-penicillamine5]enkephalin (DPDPE, 1 PM). The highly selective and potenr S-opioid receptor agonist, [D-Ser'(O-tert-butyl),Leu5]enkephalyl-Thr6 (DSTBULET). and the a-opioid receptor agonist, U50-488, were ineffective in concentrations up to 3 pM. Naloxone reversed equally well the inhibitory effects of DPDPE and of DAGO, indicating the involvement of functional F-opioid receptors. The isoprenaline (1 PM)-stimulated adenylate cyclase activity in cultured glial cells. which exceeded that in neurons about IO-fold. was not affected by opioids. Therefore, opioids were ineffective in rat brain slices probably due to the fact that cyclic AMP production induced by b-adrenoceptor activation occurs primarily in the glial cells, where it is not subject to inhibition by opioids. These data indicate for the first time the existence of an interaction between functional p-opioid receptors and P-adrenoceptors on striatal neurons of the rat.
American Journal of Pharmacology and Toxicology, 2007
Naloxone benzoylhydrazone (NalBzoH) is often used as a nociceptin opioid peptide (NOP) receptor antagonist. However, NalBzoH is also a mixed µ antagonist/κ and δ opioid agonist and its actions at the NOP receptor range from an antagonist to partial agonist, depending on the effector response/system studied. We now report that NalBzoH activates endogenously expressed κ 3 opioid, but not NOP, receptors to stimulate extracellular signal-regulated protein kinases 1/2 and, subsequently, to mediate changes in the expression of tyrosine hydroxylase and G protein-coupled receptor kinase 2 in SH-SY5Y human neuroblastoma cells. Furthermore, pretreatment with NalBzoH produces homologous desensitization of the κ 3 opioid receptor as well as heterologous desensitization of the NOP receptor. In contrast, pretreatment with the NOP agonist, orphanin FQ/nociceptin (OFQ/N), desensitizes only NOP but not the NalBzoH response, suggesting the involvement of a receptor, distinct from NOP, in mediating the actions of NalBzoH in SH-SY5Y cells.
Coupling of the cloned rat κ-opioid receptor to adenylyl cyclase is dependent on receptor expression
Neuroscience Letters, 1997
This study describes the coupling of the recombinant rat k-opioid receptor expressed in Chinese hamster ovary (CHO) cells to adenylyl cyclase and the effects of receptor density. The binding of [ 3 H]diprenorphine ([ 3 H]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 (B max ) declined from 231 ± 24 (early) to 31 ± 2 fmol/mg protein (late) but the equilibrium dissociation constant (K d ) did not change. Spiradoline dose dependently displaced [ 3 H]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 pIC 50 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 mM), compounds with activity at k-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 k-agonist specific. Collectively, these data suggest that in CHO cells, k-opioid receptor coupling to adenylyl cyclase is dependent on receptor expression levels.
The opioid receptor binding of dezocine, morphine, fentanyl, butorphanol and nalbuphine
Life Sciences, 1993
The ability of morphine, fentanyl, butorphanol, nalbuphine, and dezocine to compete with radiolabeled ligands for binding at the mul, mu 2, kappaa, and delta opioid receptors and the sigma receptor was characterized. In the absence of sodium, the potency of opioid receptor competition at each receptor site was found to be: mu~-fentanyl > butorphanol > morphine __> dezocine = nalbuphine; mu 2-butorphanol > fentanyl > nalbuphine > morphine = dezocine; kappa I-butorphanol > nalbuphine > > morphine.>> dezocine > fentanyl; and delta-butorphanol > nalbuphine ~ dezocine > morphine > fentanyl. For all five compounds, competition at the sigma receptor was weak, with nalbuphine and dezocine having I~s of approximately 0.5/~M and the other opioids having K~s of greater than 1 pM. Since the presence of 100 mM NaC1 during the competitive binding decreased the K i, to varying degrees, of all five opioids at the mu~ and delta receptors and of some of the opioids at the mu 2 and kappa 1 receptors, the five compounds studied appear to differ in efficacy at the five receptor sites. Martin (for review see 1) first suggested that the effects of the opioid analgesic agents were mediated by three distinct sets of receptors, which he termed the mu, kappa, and sigma receptors. Later, the discovery that the two enkephalin pentapeptides met-enkephalin and leu-enkephalin behaved differently from morphine in the guinea pig ileum and mouse vas deferens led to the postulation of the existence of a fourth opioid receptor, the delta receptor (2). More recently, the existence of two types of mu receptors has been established: the very high affinity, low density, mu 1 receptor subtype characterized by Pasternak and co-workers (3,4) that appears to mediate supraspinal analgesia and the lower affinity, high density, mu 2 receptor subtype that appears to mediate respiratory depression, physical dependence, and inhibition of gastrointestinal motility (5-8). There are also some indications that there are multiple kappa receptors (11,12). With the exception of morphine, no information exists as to the interaction of the clinically relevant opioid analgesics at the mu 1 and mu 2 receptor subtypes, and information on their binding to kappa, delta and sigma receptores is scanty. We have therefore examined the interaction of morphine, fentanyl, butorphanol, nalbuphine, and dezocine with the mul, mu 2, kappa 1, and delta opioid receptors and with sigma receptors.
κ-Opioid receptors are differentially labeled by arylacetamides and benzomorphans
European Journal of Pharmacology, 2004
Using Chinese Hamster Ovary cell membranes that stably expressed the human n-opioid receptor, we investigated the hypothesis that n 1and n 2 -opioid receptors, historically defined by their phrmacological selectivity for either arylacetamides or benzomorphans are, in fact, different affinity states or binding sites on the same n-opioid receptors. Receptor binding studies showed that GTPgS potently inhibited binding, compared to virtually no inhibition of [ 3 H]bremazocine binding. Saturation binding experiments showed a three-fold decrease in [ 3 H]U69,593 affinity in the presence of GTPgS, but GTPgS had no effect on [ 3 H]bremazocine affinity. The n-opioid receptor antagonist nor-binaltorphimine had a fourfold higher affinity for [ 3 H]U69,593-labeled receptors than for [ 3 H]bremazocine-labeled receptors. Functional selectivity studies, measuring the stimulation of [ 35 S]GTPgS agonist-induced binding, showed a significantly higher U69,593-induced G protein-receptor activation in comparison to the stimulation observed with bremazocine. These results suggest that pharmacologically defined 1n-opioid receptor subtypes may be different affinity states of the same receptor. D
The role of subtypes of the opioid receptor in the anxiolytic action of chlordiazepoxide
Neuropharmacology, 1998
Previous studies have shown that the opiate antagonist naloxone blocks the anxiolytic-like effects of benzodiazepines in several models of anxiety, including the elevated plus-maze. Although naloxone preferentially binds to the mu opioid receptor, its selectivity is rather low. The opioid receptor subtype important for anxiolytic-like actions of benzodiazepines in the plus-maze remains, therefore, unknown. In the present experiments, the ability of antagonists selective for subtypes of the opioid receptor to block the anxiolytic-like effects of chlordiazepoxide in the elevated plus-maze was evaluated in Swiss mice. Chlordiazepoxide, 5 mg/kg, increased the proportion as well as the number of open arms entries without modifying closed arms entries. Lower doses of the benzodiazepine were ineffective. The mu receptor antagonist beta-funaltrexamine, 10 and 20 mg/kg, the delta antagonist naltrindole, 10 mg/kg, and the kappa antagonist nor-binaltorphimine, 2.5 and 5 mg/kg, were then combin...
European Journal of Pharmacology, 1992
In slices of rat nucleus accumbens, olfactory tubercle, frontal cortex and mediobasal hypothalamus exposed to dopamine (DA), the activation of DA D~ receptors stimulated cyclic AMP (cAMP) formation whereas, in nucleus accumbcns slices only, activation of D~ receptors appeared to inhibit Dj receptor-stimulated adenylate cyclase at the same time. Activation of/x-opioid receptors by [D-Ala2,MePhe4,Gly-olS]enkephalin (DAMGO; 1 #M), but not of 6-opioid receptors by 1 ttM [D-Pen2,D-Pen5]enkephalin (DPDPE), inhibited (by 35-40%) DA-stimulated cAMP production in slices of nucleus accumbens and olfactory tubercle. When adenylate cyclase was stimulated by selective D l receptor activation, i.e. by DA in the presence of (-)-sulpiride, DPDPE reduced cAMP formation (by about 45%) in nucleus accumbens slices but not in slices of the other brain dregions. The K-agonist, U 50,488, did not affect DA-or D 1 receptor-stimulated adenylate cyclase activity in any of the brain regions. Preincubation of nucleus accumbens slices with the irreversible 6-1igand, fcntanyl isothiocyanate (FIT; 1 /xM), not only antagonized the inhibitory effect of DPDPE but also prevented the antagonism by naloxonc of the inhibitory cffect of DAMGO. Therefore, in nucleus accumbens opioids may inhibit DA-sensitive adenylate cyclase through activation of a /x/g-opioid receptor complex, whereas in olfactory tubercle/x-receptors appear to mediate the inhibition of adenylate cyclasc activity. Opioids do not sccm to affect DA-stimulated cAMP formation in frontal cortex and mediobasal hypothalamus.
effect of α-adrenergic blockers on naloxone-binding in braiN
Biochemical Pharmacology, 1974
In several recent studies, we have shown that a-adrenergic blocking agents possess a degree of antinociceptive activity themselves, markedly increase morphine's analgetic and toxic effects, and effectively suppress the expression of the narcotic withdrawal syndrome in the rat (1,2,3). Since B-adrenergic blocking agents and numerous other agents possessed none of these properties, these data suggest that the narcotics and a-adrenergic blockers may be closely related. However, since all of the data up to the present are indirect, we cannot rule out the possibility that the interaction we have observed between these two classes of drugs merely represents the summation of two totally independent processes. The purpose of the studies described in this paper was to obtain more direct evidence of an interaction between morphine and a-adrenergic blocking agents. Pert and Synder (4,5) previously have demonstrated that stereospecific binding of naloxone occurs in rat brain homogenates and that various narcotic agonists and antagonists effectively reduce naloxone-binding. We have employed this preparation to examine whether a-adrenergic blockers would displace naloxone from the so-called "opiate receptor."