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PubMed2000

Synthesis and opioid receptor affinity of morphinan and benzomorphan derivatives: mixed kappa agonists and mu agonists/antagonists as potential pharmacotherapeutics for cocaine dependence.

This report concerns the synthesis and preliminary pharmacological evaluation of a novel series of kappa agonists related to the morphinan (-)-cyclorphan (3a) and the benzomorphan (-)-cyclazocine (2) as potential agents for the pharmacotherapy of cocaine abuse. Recent evidence suggests that agonists acting at kappa opioid receptors may modulate the activity of dopaminergic neurons and alter the neurochemical and behavioral effects of cocaine. We describe the synthesis and chemical characterization of a series of morphinans 3a-c, structural analogues of cyclorphan [(-)-3-hydroxy-N-cyclopropylmethylmorphinan S(+)-mandelate, 3a], the 10-ketomorphinans 4a,b, and the 8-ketobenzomorphan 1b. Binding experiments demonstrated that the cyclobutyl analogue 3b [(-)-3-hydroxy-N-cyclobutylmethylmorphinan S(+)-mandelate, 3b, MCL-101] of cyclorphan (3a) had a high affinity for mu, delta, and kappa opioid receptors in guinea pig brain membranes. Both 3a,b were approximately 2-fold more selective for the kappa receptor than for the mu receptor. However 3b (the cyclobutyl analogue) was 18-fold more selective for the kappa receptor in comparison to the delta receptor, while cyclorphan (3a) had only 4-fold greater affinity for the kappa receptor in comparison to the delta receptor. These findings were confirmed in the antinociceptive tests (tail-flick and acetic acid writhing) in mice, which demonstrated that cyclorphan (3a) produced antinociception that was mediated by the delta receptor while 3b did not produce agonist or antagonist effects at the delta receptor. Both 3a,b had comparable kappa agonist properties. 3a,b had opposing effects at the mu receptor: 3b was a mu agonist whereas 3a was a mu antagonist.

Acetic Acid↗
PubMed1980

Possible role of distinct morphine and enkephalin receptors in mediating actins of benzomorphan drugs (putative kappa and sigma agonists).

The binding of many opiates and enkephalins to enkephalin (delta) and morphine (mu) receptors was compared by using three different binding assays: (i) 125I-labeled[D-Ala2, D-Leu5]enkephalin or 125I-labeled[D-Ala2,N-Me-Phe4,Met(O)5ol]-enkephalin to brain membranes; (ii) [3H]ethylketocyclazocine to brain membranes; and (iii) [3H]diprenorphine and [3H]naloxone to neuroblastoma cell and brain membranes, respectively. According to their relative binding potencies and the effects of Na+ and GTP on the binding to these two receptors, opiates and enkephalins can be classified into seven classes: (i) morphine-type mu agonists; (ii) enkephalin-type delta agonists; (iii) mixed agonists-antagonists; (iv) putative kappa agonists; (v) putative sigma agonists; (vi) nalorphine-type antagonists; and (vii) opiate antagonists. Studies with [3H]ethylketocyclazocine do not reveal specific kappa receptors distinct from those already described that bind morphine and enkephalins. The benzomorphan analogs ketocyclazocine and ethylketocyclazocine (putative kappa agonists) and N-allylnormetazocine (putative sigma agonist) bind to morphine (mu) and enkephalin (delta) receptors with similarly high affinities. The potency of putative kappa agonists, measured by competition with binding of the 3H-labeled antagonist, is greatly reduced by the presence of Na+ and GTP; the "Na+ and GTP ratios" are similar to those of morphine and enkephalins. However, Na+ and GTP greatly decrease the potency of binding of putative sigma agonists to enkephalin receptors but only slightly decrease the binding to morphine receptors. These data suggest that putative kappa agonists have agonistic activity toward both receptors, whereas putative sigma agonists behave as agonists for enkephalin receptors but have antagonist activity for morphine receptors. Mixed agonist-antagonists also show smaller difference in affinity to both receptors. These findings may have important implications for understanding the differences in the pharmacological effects of these drugs.

Animals↗
PubMedDate not supplied

Identification of glucuronide metabolites of benzomorphan narcotic analgesic drugs in bile from the isolated perfused rat liver by gas chromatography and mass spectrometry.

The metabolism of four benzomorphan compounds was studied in the isolated perfused rat liver, and glucuronide metabolites were identified by combined gas chromatography-mass spectrometry (GC/MS). Cyclazocine, ketocyclazocine, volazocine, and pantazocine were each added to the perfusate of the isolated perfused rat liver and the bile collected for 3 hours. The residue from evaporation of the bile was derivatized with the dimethylsulfoxide anion and methyl iodide, and the permethylated glucuronide metabolites were identified by GC/MS. The four compounds were hydroxylated by the liver and excreted in the bile as phenolic glucuronides. For example, permethylated hydroxycyclazocine glucuronide had a mass spectrum with a molecular ion at m/e 533 and fragment ions at m/e 301 (aglycone), m/e 260 (loss of cyclopropyl group) and prominent ions at m/e 232, 201, 169, 141, and 101 caused by fragmentation of the permethylated glucuronic acid moiety. Perdeuteriomethylation demonstrated that pentazocine, volazocine, and cyclazocine were further metabolized by methylation of one hydroxy substituent and glucuronidation on the other. Pentazocine, cyclazocine, and ketocyclazocine were also metabolized to phenolic glucuronides of the parent drugs. N-deakylated metabolites of pentazocine, volazocine, and cyclazocine were identified both as permethylated glucuronic acid conjugates and as the trimethylsilyl derivatives of the aglycones, obtained by enzymatic hydrolysis on the conjugates in bile.

Analgesics, Opioid↗
PubMed1985

Differentiating aspects of opioid receptor binding by [3H](-) (1R,5R,9R,2''S)-5,9-dimethyl-2-tetrahydrofurfuryl-2'-hydroxy-6,7- benzomorphan hydrochloride ([3H]Mr 2034), a drug preferentially acting on kappa-receptors.

Receptor binding experiments with masking of mu- and delta-receptors in the presence of an excess of unlabelled dihydromorphine and [D-Ala2, D-Leu5]enkephalin have been carried out. They indicate that 12 to 17% of original high affinity binding of [3H]Mr 2034 [-)(1R,5R,9R,2"S)-5,9-dimethyl-2-tetrahydrofurfuryl-2'-hydroxy-6, 7-benzomorphan hydrochloride), an opioid kappa-agonist, could then be detected as kappa-receptor sites in brain membranes both from untreated rats and from rats pretreated with naloxazone, too. Because of the irreversible blockade of the high affinity binding sites by naloxazone (naloxone hydrazone) treatment, the masking effects of mu- and delta-selective ligands seem to be mediated by the low affinity binding sites of these opioid receptor types. As could be shown before with [3H]Mr 2034, another kappa-agonist, [3H]bremazocine does not seem to be affected in its binding properties by naloxazone treatment of the rat in vivo. Displacement studies with several opioid agonists and antagonists, [3H]Mr 2034 and [3H]ethylketocyclazocine as radioligands in brain membranes from naloxazone treated rats and untreated controls provided further support for the evidence of two different kappa-receptors.

Animals↗
PubMed1983

[Mr 1268--a new furylmethyl-substituted benzomorphan. Comparison of its effects with pentazocine and placebo in a double-blind study].

Mr 1268 (alpha-5,9-dimethyl-2(3-methyl-3-methylfuryl)-2-hydroxy-6, 7-benzomorphan) was tested in two dosages (15 mg and 30 mg) at random on a total of 200 patients with severe postoperative pain in a double blind study against pentazocine and placebo. The analgesic effect of 30 mg Mr 1268 and 30 mg pentazocine compared with placebo was statistically significant 15 min after intramuscular injection. At the dosage applied no major respiratory or circulatory effects were observed in the patients. The minimal changes in the systolic blood pressure were of no statistical significance. Side-effects observed in many patients in the verum group were miosis and transpiration. For all other side-effects there was no statistically significant difference between placebo and the verum group or among the various verum groups.

Adult↗
PubMed1982

Some observations on the effects of enantiomers of two benzomorphan narcotic antagonists and atropine on analgesia, tremor and hypothermia produced by oxotremorine.

The action of the benzomorphan narcotic antagonists Mr-1452 and Mr-2266 and their respective (+) isomers Mr-1453 and Mr-2267 as well as the antimuscarinic agent atropine upon oxotremorine (OTMN)-induced analgesia, tremor, and hypothermia were investigated in mice. The (+) isomers Mr-1453 (1.0 mg kg-1 i.p.) and Mr-2267 (2.0 mg kg-1 i.p.), but not the (-) isomers (Mr-1452 and Mr-2266) in doses up to 2.0 mg kg-1 i.p. after 30 min pretreatment produced a significant and parallel shift in OTMN's analgesic dose-response line, assessed by the hot plate test (55 degrees C). None of the isomers tested produced any significant change in OTMN induced tremor or hypothermia. This contrasted with atropine (0.5 mg kg-1 i.p.) which antagonized all three pharmacological parameters. The present data indicate that OTMN-induced analgesia in mice may involve a neuronal substrate which, at least partly, differs from those subserving tremor and hypothermia. In addition it supports the notion that cholinergic analgesia exhibits stereospecific sensitivity to the (+) isomers of narcotic antagonists.

Animals↗
PubMed1980

Interactions of narcotics and their antagonists with human serum esterase. VIII: structure-activity relationships of benzomorphans.

N-alkylbenzomorphans follow the pattern established in our earlier papers for the interaction of opiates with human serum esterase: they have affinity for both the substrate-binding site of the enzyme and an allosteric site at which agonistic drugs accelerate enzyme action. Affinity for the substrate-binding site is a function of the hydrophobicity of the drug, while affinity to the allosteric site is increased by alkyl groups at N and at C--5 and decreased by a 2'-methoxyl group or by either a methyl or a hydroxyl group in the 9 beta position. The absolute D configuration (corresponding to that of natural morphine) appears to be more sensitive to factors modifying affinity. All but three of the benzomorphans studied are agonists; all agonists have lower affinity for the allosteric site than antagonists.

Benzomorphans↗
PubMed1980

Synthesis and analgesic activity of N-substituted 6,7-benzomorphans.

Some new N-substituted 6,7-benzomorphans were prepared and tested for analgetic activity. The compounds (I) and (II), which proved the most active in a preliminary screening, were submitted to a more detailed investigation, and their ED50 was determined in mice by the phenylquinone, hot-plate and tail-pinch tests. Studies of acute toxicity and physical dependence capacity were also performed.

Analgesics↗
PubMed1994

Synthesis of 2'-heptylcarbamoyloxy-2-methyl-6,7-benzomorphan: a new analogue of heptylphysostigmine (MF 201).

The synthesis of 2'-heptylcarbamoyloxy-2-methyl-6,7-benzomorphan is described. The compound is structurally related to the cholinesterase inhibitor heptylphysostigmine (MF 201) because the angular methyl group of the esoroline nucleus has been changed into a bridging carbon and the anilinic nitrogen has been replaced by a methylene group. This compound proved to be a potent cholinesterase in vitro inhibitor.

Benzomorphans↗
PubMed1993

Correlation between potentiation of neurogenic twitch contraction and benzomorphan sigma receptor binding potency in the mouse vas deferens.

The effects of sigma receptor ligands on the neurogenic twitch contraction in the ddY mouse vas deferens were studied. In functional studies, (+)-N-allylnormetazocine ((+)-SKF-10,047) and (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-3-PPP) potentiated neurogenic twitch contractions in a concentration-dependent manner. The potentiation by each (+) enantiomer was significantly more potent than that by the respective (-) enantiomer. In addition, haloperidol and (+/-)-pentazocine also potentiated neurogenic twitch contractions. The order of potentiating ability was: haloperidol > (+/-)-pentazocine > (+)-3-PPP > (-)-3-PPP > (+)-SKF-10,047 > (-)-SKF-10,047. In contrast, other sigma receptor ligands, 1,3-di(2-tolyl)guanidine (DTG) and rimcazole, suppressed this twitch contraction. In addition, rimcazole significantly antagonized the (+)-SKF-10,047-induced potentiation at concentrations which did not affect contractions per se. Furthermore, binding studies showed that the kinetic parameters and the inhibitory potencies of sigma receptor ligands for the binding of [3H](+)-SKF-10,047 in the mouse vas deferens were similar to those in the guinea pig brain. The order of potency of sigma receptor ligands to potentiate the neurogenic twitch contraction in the mouse vas deferens was significantly correlated with the potency to inhibit [3H](+)-SKF-10,047 binding in both mouse vas deferens and guinea pig brain. These results indicate that sigma receptor ligands regulate the neurogenic twitch contraction, which is mediated by rimcazole-sensitive benzomorphan-type sigma receptors.

Animals↗
PubMed1994

Antipodal alpha-N-(methyl through decyl)-N-normetazocines (5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphans): in vitro and in vivo properties.

The enantiomeric (-)- and (+)-N-(methyl through decyl) normetazocines (5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphans) were synthesized and their in vitro and in vivo activities determined. Increasingly bulky enantiomeric N-alkyl homologs were prepared until their interaction with the sigma 1 receptor decreased and their insolubility became a hindrance to their evaluation in vivo and/or in vitro. The (-)-methyl, -pentyl, -hexyl, and -heptyl homologs were essentially as potent as, or more potent than, morphine in the tail-flick, phenylquinone, and hot-plate assays for antinociceptive activity; the (-)-propyl homolog had narcotic antagonist activity between that of nalorphine and naloxone in the tail-flick vs morphine assay, and it also displayed antagonist properties in the single-dose suppression assay in the rhesus monkey. The antinociceptively potent (-)-heptyl homolog did not substitute for morphine in monkeys but did show morphine-like properties in a primary physical-dependence study in continuously infused rats. All five potent compounds showed high affinity for the mu opioid receptor from both rat and monkey preparations and the kappa opioid receptor (< 0.05 microM), and all except the (-)-methyl homolog interacted reasonably well at the delta receptor (K(i) < 0.1 microM). The (-)-propyl compound was equipotent (K(i) 1.5-2.0 nM) at mu and kappa receptors. The pattern of interaction of the (-)-enantiomeric homologs with mu receptors from rat and monkey preparations was similar, but not identical. The enantioselectivity of the homologs for mu receptors was greater in the rat than in the monkey preparation for all but the N-H and butyl compounds, and the enantioselectivity of the lower homologs (methyl through butyl) for the mu (monkey) receptor was greater than for the kappa or delta receptors. However, bulkier homologs (hexyl through decyl) displayed higher enantioselectivity at kappa or delta receptors than at the mu (monkey) receptor. The (+)-butyl through (+)-octyl homologs were essentially equipotent with, or more potent than, (+)-pentazocine at the sigma receptor. Only the (+)-H and (+)-methyl homologs had high affinity (< 0.05 microM) at PCP binding sites.

Amino Acid Sequence↗
PubMed1987

Interaction of a benzomorphan opiate with acetylcholinesterase and the nicotinic acetylcholine receptor.

The benzomorphan opiate, (-)N-allynormetazocine [(-)ANMC, (-)SKF10047], has been shown previously to bind two distinct sites on acetylcholine receptor (AChR)-rich membranes from Torpedo electroplaque. The low affinity site seems to correspond to the site for noncompetitive blockers on the AChR. The high affinity site, which can be photoaffinity labeled using UV irradiation, was distinct from this site. We show here, using a variety of techniques, that the high affinity binding site for (-)ANMC is on the acetylcholinesterase (AChE) associated with these membranes. The Triton X-100-solubilized peptide photolabeled with (-)[3H]ANMC co-migrates with acetylcholinesterase activity on velocity sucrose gradient centrifugation and fast protein liquid chromatography. In addition, the labeled peptide cannot be precipitated with monoclonal or polyclonal antibodies raised against the nicotinic AChR but can be precipitated with anti-AChE antibodies. Localization of the binding site on AChE was confirmed by photolabeling of and reversible binding to the 11 S AChE purified from Torpedo californica. The binding and photolabeling had characteristics and affinity similar to those for the high affinity binding site in Torpedo electroplaque membranes. Competition studies with specific AChE inhibitors suggest that the binding site may be the catalytic site of the enzyme, which exists on the 66-kDa globular protein. The effect of (-) and (+)ANMC on AChE activity was also investigated. ANMC inhibited AChE activity at micromolar concentrations in a stereoselective fashion, with the (-)isomer exhibiting a 2-fold higher affinity than the (+) isomer. The inhibition was consistent with a competitive blockade of AChE activity.

Acetylcholinesterase↗
PubMed1986

Mechanism of binding of a benzomorphan opiate to the acetylcholine receptor from Torpedo electroplaque.

The mechanism of binding of the benzomorphan opiate, (-)-N-allylnormetazocine [(-)-ANMC], to Torpedo acetylcholine receptor (AcChR)-rich membranes was investigated. Using a centrifugation assay, two equilibrium binding affinities were observed with KD values of 0.4 and 2 microM. The KD and the apparent Bmax of the higher affinity component were decreased by cholinergic agonists and antagonists but not by alpha-bungarotoxin alone. The high affinity binding site (KD = 0.4 microM) was found to be distinct from the binding site for tetracaine, a noncompetitive blocker. The apparent association rate constant was essentially independent of receptor concentration both in the presence and absence of the cholinergic agonist, carbamoylcholine. When carbamoylcholine was equilibrated with the AcChR prior to (-)-[3H]ANMC addition, the association rate constant was 2- to 3-fold greater than in the absence of cholinergic effectors. When carbamoylcholine and (-)-[3H]ANMC were added simultaneously to AcChR-rich membranes, association was too rapid to resolve manually and binding measured at 5 sec was greater than the equilibrium level both in the presence and absence of carbamoylcholine. Binding decreased as a function of time, reaching its equilibrium level with a time constant of approximately 1 min. This effect appeared to be agonist specific since it was not observed when the antagonist, d-tubocurarine, replaced carbamoylcholine. In the absence of cholinergic ligands, dissociation of (-)-ANMC was biphasic (t1/2 values of less than 5 sec and approximately 2.5 min) and, in the presence of cholinergic ligands, was monophasic (t1/2 of 40 sec). The simultaneous addition of carbamoylcholine and (-)-[3H]ANMC to the membranes initially results in a biphasic dissociation (t1/2 of 5 and 30 sec) which becomes monophasic with increasing times of incubation. A mechanism is proposed involving an isomerization of the receptor-ligand complex which agrees quantitatively and qualitatively with the data.

Affinity Labels↗
PubMed1993

Identification of the benzomorphan opiate binding site on the catalytic subunit of acetylcholinesterase.

The interaction of a benzomorphan opiate with the active site of the catalytic subunit of acetylcholinesterase was studied using photoaffinity labeling. UV irradiation of (-)-N-[3H]allylnormetazocine bound to Torpedo acetylcholinesterase resulted in covalent incorporation of 60-70% of the bound ligand. The labeled catalytic subunit was subjected to chemical cleavage with cyanogen bromide and proteolytic degradation with trypsin, chymotrypsin, and staphylococcal V8 protease. The resulting peptide fragments were purified by high performance liquid chromatography and sequenced in the gas phase. The label was not stable under the conditions of the sequencing, but a peptide fragment consisting of Gln74 to Glu82 was reproducibly labeled. These amino acids are located at the rim of a gorge leading to the active site of the enzyme. Molecular modeling studies then demonstrated that these residues can be placed within van der Waals contact of the (-)-N-[3H]allylnormetazocine molecule while it is bound to the active site of the enzyme.

Acetylcholinesterase↗
PubMed1999

Stereoselective synthesis and receptor binding of conformationally restricted and flexible 2,4-disubstituted 1,3-dioxanes derived from benzomorphans.

The key steps in the stereoselective synthesis of the tricyclic aminomethyl derivatives 19 and 20 and the aminoethyl substituted 1,3-dioxanes 24 and 25 are nucleophilic addition of aryllithium intermediates to the nitroalkene 13, intramolecular transacetalization of the addition products 15 and 16 (only for the tricyclic derivatives 19 and 20) and subsequent reduction of the nitro group. The affinities of the secondary and tertiary amines 19c,d, 20c,d, 24c,d, and 25c,d for the ion channel binding site of the NMDA receptor, for mu-, kappa-, and sigma-receptors have been investigated. In the group of tricyclic compounds only 19d shows remarkable sigma-receptor affinity (Ki = 21.6/1.10 microM). In the 1,3-dioxane series the moderate mu- (Ki = 27.8 microM) and kappa-receptor affinity (Ki = 36 microM) as well as the high sigma-receptor affinity (Ki = 3.3 microM) of the (S,S,S)-configurated methylamine 24c should be emphasized. The pentan-1-ol 26, the side product isolated during the synthesis of 24c, is of particular interest because of its considerable affinity to mu- (Ki = 16.0 microM), kappa- (Ki = 2.8 microM), and sigma-receptors (Ki = 14.5/1.26 microM). The biphasic competition curves obtained during sigma-receptor binding studies of 19d and 26 (two Ki values) may be explained by different interaction with sigma-receptor subtypes.

Amines↗