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Biomedical subjects

A E Jacobson

Publications and source records attributed to A E Jacobson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Synthesis, phencyclidine-like pharmacology, and antiischemic potential of meta-substituted 1-(1-phenylcyclohexyl)-1,2,3,6-tetrahydropyridines.

A series of 1-[1-arylcyclohexyl]-1,2,3,6-tetrahydropyridines were prepared by the reaction between 1-(1-cyanocyclohexyl)-1,2,3,6-tetrahydropyridine (1) and an appropriately substituted Grignard reagent. The resulting compounds were tested for their phencyclidine binding site affinities. Selected compounds were then tested for their ability to produce ketamine appropriate responding in monkeys and/or to show neuroprotective effects in a baby rat hypoxia/ischemia model. While it was found that binding site affinity correlated well with discriminative stimulus effects, it was found to be a poor indicator of neuroprotective efficacy within this series.

Animals↗
PubMed1990

Synthesis and evaluation of N-substituted cis-N-methyl-2-(1-pyrrolidinyl)cyclohexylamines as high affinity sigma receptor ligands. Identification of a new class of highly potent and selective sigma receptor probes.

Certain benzeneacetamides [(-)- and (+)-cis-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]benzeneacetamide] were recently reported to be potent sigma receptor ligands. In order to determine whether efficacy for the sigma receptor could be improved, a series of compounds related to the benzeneacetamides, N-substituted cis-2-(1-pyrrolidinyl)-N-methylcyclohexylamines, were synthesized and their structure-activity requirements were determined. The compounds were synthesized by starting with the previously reported (+/-)-, 1S,2R-(+)-, and 1R,2S-(-)-cis-2-(1-pyrrolidinyl)-N-methylcyclohexylamines. Analysis of sigma ([3H](+)-3-PPP), kappa ([3H]bremazocine and [3H]U69,593), dopamine-d2 ([3H](-)-sulpiride), and phencyclidine (PCP) ([3H]TCP) receptor binding in guinea pig brain revealed a number of highly potent and selective sigma receptor ligands. Notably, 1S,2R-cis-(-)-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-(2-naphthyl) acetamide [(-)-29] (Ki = 8.66 +/- 0.35 nM), (+/-)-cis-2-amino-4,5-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide [(+/-)-17] (Ki = 11 +/- 3 nM), 1S,2R-(-)-cis-N-methyl-N-[2-(3,4-dichlorophenyl)ethyl]-2-(1-pyrrolidinyl ) cyclohexylamine [(-)-44] (Ki = 1.3 +/- 0.3 nM), and 1R,2S-(+)-cis-N-methyl-N-[2-(3,4-dichlorophenyl)ethyl]-2-(1-pyrrolidinyl ) cyclohexylamine. [(+)-44] (Ki = 6 +/- 3 nM) exhibited very high affinity at sigma receptors, by displacement of [3H]-(+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [( 3H]-(+)-3-PPP). These compounds showed insignificant affinity for kappa, dopamine, or PCP receptors, making them valuable tools for the study of sigma receptors. Furthermore, these compounds also exhibited enantioselectivity ranging from 5-fold for (+)- and (-)-44 to 160-fold for (+)- and (-)-29. Several other compounds showed equivalent selectivity but displayed lower sigma receptor affinity.

Animals↗
PubMed1990

Anti-opioid receptor antibody recognition of a binding site on brain and leukocyte opioid receptors.

Opioid receptors reportedly exist on neuronal tissue of central and peripheral origin as well as on cells of the immune system. Previously, an opioid receptor has been purified from the neuroblastoma x glioma hybrid cell line, NG108-15 cells. In an effort to compare these results with opioid receptors isolated from primary neuronal tissue, we employed a methodology based on the molecular recognition theory to develop a monoclonal antibody which was used to isolate and biochemically characterize murine brain opioid receptors. We herein report the purification of an opioid receptor from mouse brain with a molecular weight of 65,000 daltons (range was 62-70 kD under reducing conditions) using a monoclonal antibody to an (the) opioid receptor. In situ labeling experiments with the delta-class selective opioid receptor affinity ligand, cis-(+)-3-methylfentanylisothiocyanate (SUPERFIT) of brain membrane confirmed these observations. Moreover, SUPERFIT, when coupled to the binding site, could block the recognition of the receptor by the monoclonal antibody. However, the selective, mu-class opioid receptor affinity reagent, 2-(p-ethoxybenzyl)-1-N,N-diethylaminoethyl-5-isothiocyanatobenz imidazole was ineffective at masking the binding site from recognition by the monoclonal antibody. Likewise, opioid-like receptors were purified from murine leukocytes which migrated at a molecular weight of 58,000 daltons under nonreducing conditions and 70,000 daltons under reducing conditions. In addition, immunoaffinity-purified receptor is shown to specifically bind the delta-class-selective opioid ligand, cis-(+)-3-methylfentanylisothiocyanate as well as the endogenous opioid peptides, beta-endorphin and [Met]-enkephalin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Apparent affinity of opioid antagonists in morphine-treated rhesus monkeys discriminating between saline and naltrexone.

In morphine-treated (3.2 mg/kg/day) rhesus monkeys discriminating between s.c. injections of 0.01 mg/kg of naltrexone and saline while responding under a fixed-ratio schedule of stimulus-shock termination, the apparent affinity of antagonists for opioid receptors was estimated using two different methods: 1) substitution studies in which cumulative doses of drug were administered to monkeys that received morphine 3 hr before the session and 2) studies in which single doses of antagonists were administered before cumulative doses of agonists in monkeys that had received saline 3 hr before the session. The ED50 values from the substitution study were compared to apparent pA2 values determined when antagonists were administered before agonists. Apparent affinities (pA2) for antagonists, estimated by their capacity to prevent the effects of the opioid agonist alfentanil, were: naltrexone = 8.69, naloxone = 7.78, quadazocine = 7.55, nalorphine = 7.31 and naltrindole = 5.29. The pA2 values were highly correlated (r = 0.94) with ED50 values determined in substitution studies. These results demonstrate that substitution by opioid antagonists for the naltrexone discriminative stimulus in morphine-treated monkeys provides a good estimate of affinity for opioid mu receptors as supported by independent pA2 analyses. These data also suggest affinity of opioid antagonists for opioid mu receptors is not changed in monkeys treated daily with 3.2 mg/kg of morphine and, furthermore, support the notion that binding to opioid receptors is the mechanism, by which antagonists precipitate withdrawal in opioid-dependent monkeys.

Animals↗
PubMed1989

Pharmacological activities of optically pure enantiomers of the kappa opioid agonist, U50,488, and its cis diastereomer: evidence for three kappa receptor subtypes.

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)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1989

Effects of metaphit on phencyclidine and serotonin2 receptors.

We have investigated whether metaphit, a derivative of phencyclidine (PCP) which irreversibly binds to a population of PCP receptor sites in rat brain, blocks PCP-induced head-twitch response which is produced through serotonin2 (5-HT2) receptors, and also whether metaphit decreases the capacity of 5-HT2 receptors. Metaphit (1 mumol/rat) had decreased the intensity of PCP-induced head-twitch response and had depleted both PCP and 5-HT2 receptors by 24 h after administration, but it failed to block 5-HT agonist 5-methoxy-N,N-dimethyltryptamine-induced 5-HT1A receptor-dependent behaviors. These results reconfirmed our hypothesis that PCP and 5-HT2 receptors may have very similar binding sites.

Animals↗
PubMed1989

Synthesis and evaluation of optically pure [3H]-(+)-pentazocine, a highly potent and selective radioligand for sigma receptors.

Tritium-labeled (+)-pentazocine ([3H]-1b) of specific activity 26.6 Ci/mmol was synthesized in 3 steps starting with (+)-normetazocine (2) of defined optical purity. [3H]-1b has been characterized as a highly selective ligand for labeling of sigma receptors. Competition data revealed that [3H]-1b could be displaced from guinea pig brain membrane preparations with a number of commonly used sigma receptor ligands. [3H]-1b exhibited saturable, enantioselective binding with a Kd of 5.13 +/- 0.97 nM and a Bmax of 1146 +/- 122 fmol/mg protein. Phencyclidine (PCP) displaced [3H]-1b with low affinity while MK-801 was inactive, thus indicating insignificant activity at the PCP-binding site; apomorphine failed to displace [3H]-1b indicating lack of dopamine receptor cross-reactivity. Since the affinity of [3H]-1b is about 6 times that of the two commonly employed sigma ligands ((+)-3-[3H]PPP and [3H]DTG) and since it is more selective for sigma receptors than the benzomorphan [3H]SKF-10,047, it represents the first example of a highly selective benzomorphan based sigma receptor ligand. [3H]-1b should prove useful for further study of the structure and function of sigma receptors.

Animals↗
PubMed1989

Metaphit, an isothiocyanate analog of PCP, induces audiogenic seizures in mice.

Metaphit induces audiogenic seizures in mice. The most severe clonic/tonic seizures occur 18-24 h after metaphit administration. After 48 h the incidence of the seizure episodes begin to diminish. These audiogenic seizures can be prevented by the administration of either PCP or MK-801 24 h after metaphit and 30 min prior to audio stimulation. These seizures may be due to a modulation of the PCP recognition site by metaphit which results in an enhanced probability that the NMDA/PCP ion channels are open.

Acoustic Stimulation↗
PubMed1989

Synthesis of an affinity ligand ('UPHIT') for in vivo acylation of the kappa-opioid receptor.

The isothiocyanate analog (1S,2S-trans-2-isothiocyanato-4,5-dichloro-N- methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide, 3a) of the highly selective kappa-opioid receptor agonist, U50,488, was prepared as a potential site-directed affinity ligand for acylation of kappa-opioid receptors in vivo. The isothiocyanate (3a) which we have designated UPHIT and its enantiomer (3b) were synthesized in 3 steps starting from optically pure (1S,2S)-(+)-trans-2-pyrrolidinyl-N-methyl-cyclohexylamine (4a) and its enantiomer (4b), respectively, thus defining their absolute stereochemistry. Binding in vitro of the 1S,2S enantiomer 3a to kappa receptors labelled by [3H]U69,593 was shown to occur with an IC50 value of 25.92 +/- 0.36 nM, whereas 827.42 +/- 5.88 and 115.10 +/- 1.23 nM were obtained for the IC50 value of the 1R,2R enantiomer (3b) and (+/-)-3 respectively. Intracerebroventricular (ICV) injection of 100 micrograms of (+/-)-3 into guinea-pig brain followed by analysis of remaining kappa-binding sites 24 h later revealed that (+/-)-3 depleted 98% of the kappa receptors that bind [3H]U69,593 and 40% of those that bind [3H]bremazocine. These preliminary data suggest exciting uses for these compounds in furthering our knowledge of the kappa-opioid receptor.

Acylation↗
PubMed1989

Acylation of sigma receptors by Metaphit, an isothiocyanate derivative of phencyclidine.

Pretreatment of guinea pig brain membranes with 1-[1-(3-isothiocyanatophenyl)cyclohexyl]piperidine (Metaphit) caused irreversible and differential inhibition of ligand binding to sigma (sigma) receptors. The concentration of Metaphit required to produce 50% inhibition of binding of [3H]1,3-di-o-tolylguanidine ([3H]DTG), [3H](+)-3-(3-hydroxy-phenyl)-N-(1-propyl)piperidine ([3H](+)-3-PPP), and [3H](+)-N-allylnormetazocine ([3H](+)-SKF 10,047) to sigma receptors was 2, 10 and 50 microM, respectively. This compares to a value of 10 microM for inhibition of [3H]1-[1-(2-thienyl)cyclohexyl]piperidine [( 3H]TCP) binding to phencyclidine (PCP) receptors. While Metaphit was an irreversible, non-competitive inhibitor at PCP receptors, this compound produced irreversible, competitive inhibition at sigma receptors.

Acylation↗
PubMed1989

Chronic administration of morphine and naltrexone up-regulate mu-opioid binding sites labeled by [3H][D-Ala2,MePhe4,Gly-ol5]enkephalin: further evidence for two mu-binding sites.

A variety of data support the hypothesis of an opiate receptor complex composed of distinct, yet interacting mu and delta binding sites (termed mu cx and delta cx to indicate binding sites 'in the complex'), in addition to independent mu and delta binding sites, termed mu ncx and delta ncx, to indicate binding sites 'not in the complex'. Ligand binding studies using membranes and slide-mounted sections of rat brain support the hypothesis that the irreversible mu-antagonist beta-funaltrexamine (FNA) selectively alkylates the opiate receptor complex, altering the binding of mu agonists to the mu cx binding site and the binding of [3H][D-Ala2,D-Leu5]enkephalin to the delta cx site. Previous studies demonstrated that the chronic administration of morphine to rats selectively 'upregulates' the opiate receptor complex. In contrast, the chronic administration of naltrexone upregulates several types of opioid receptors, including kappa, the delta ncx binding site, and multiple binding sites labeled by mu agonists. A prediction based upon these observations is that, using [3H][D-Ala2,MePhe4,Gly-ol5]enkephalin to label mu binding sites, chronic morphine should upregulate only the mu cx binding site, whereas chronic naltrexone should additionally up-regulate the mu ncx binding site. In this study we test and confirm this hypothesis, using sensitivity to FNA to define the mu cx binding site. The implications of these data for models of the opioid receptors and the mechanism(s) of tolerance and dependence are discussed.

Animals↗
PubMed1989

Long-term blockade of the dopamine uptake complex by metaphit, an isothiocyanate derivative of phencyclidine.

[3H]Mazindol was used to label the dopamine uptake complex in mouse striatum in vitro in the presence and absence of metaphit, an isothiocyanate derivative of phencyclidine. In some experiments, metaphit was present in the incubation fluid throughout the procedure; in other experiments it was eliminated by several washings and centrifugations. It was found that after removal of the metaphit by washing and centrifugation, the mazindol binding was not restored. Membranes that were pretreated with metaphit and washed had a lower density of mazindol binding sites than control membranes; the remaining mazindol sites had the same afinity for [3H]mazindol. These findings are in agreement with the previous studies on [3H]cocaine and [3H]methylphenidate binding. The following observations support that metaphit is irreversibly acting and not slowly dissociating from the mazindol recognition sites of the dopamine uptake carrier complex: 1) Metaphit did not change the off-rate of [3H]mazindol binding, arguing against an allosteric action at a distinct site. 2) The presence of cocaine protected the mazindol binding sites from the action of metaphit, supporting binding of metaphit and mazindol to the same site. 3) Nine hours after metaphit pretreatment and removal, the degree of inhibition of mazindol binding was the same as immediately after pretreatment, consonant with an irreversible effect of metaphit. 4) The potency of metaphit in inhibiting mazindol binding was greater under slightly alkaline conditions, consistent with acylation of the mazindol sites. Furthermore, it was found that intracerebroventricular application of metaphit did not result in a decrease in the binding of [3H]mazindol 5 hr after the administration.

Animals↗