Stimulating and inhibitory effects of the dopamine "stabilizer" (-)-OSU6162 on dopamine D2 receptor function in vitro.

The effect of (-)-OSU6162 on the incorporation of GTPgammaS(35) in the membranes of hD(2l)-transfected CHO cells was investigated. In the absence of dopamine the compound exerted a slight but significant stimulating action, suggesting a weak partial agonism. In the presence of dopamine, low concentrations (10 to 100 nM) enhanced the stimulating action of dopamine. This enhancing effect was reversed by higher concentrations of (-)-OSU6162 in a complex biphasic manner. The dopamine-enhancing action is proposed to be mediated by binding to an allosteric site with high affinity and the inhibitory component by a low-affinity binding to the orthosteric site of the dopamine receptor.

Antipsychotic properties of the partial dopamine agonist (-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine(preclamol) in schizophrenia.

BACKGROUND: In an ongoing effort to characterize the clinical pharmacologic profile of the partial dopamine agonist (-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine [(-)-3PPP], we administered it to drug-free schizophrenic patients in two consecutive studies. METHODS: In a preliminary dose-finding study, 9 patients were treated using a 6-week placebo-controlled crossover design. Then, to properly demonstrate the antipsychotic effect, we carried out an early efficacy study; here 10 patients received (-)-3PPP, 300 mg B.I.D., in a 1-week placebo-controlled crossover study. RESULTS: Dose-Finding Study: (-)-3PPP showed apparent antipsychotic effect in repeated dosing, with 300 mg B.I.D. being the most effective dose for antipsychotic action; however, the apparent antipsychotic action was not sustained for longer than 1 week, presumably because of desensitization of the receptor by the agonist. Early Efficacy Study: Positive symptoms as measured by the Psychosis Change Scale decreased in 1 week by 30% with (-)-3PPP compared to placebo, and negative symptoms measured with the Brief Psychiatric Rating Scale Withdrawal subscale decreased by 28% with the drug. In both studies, (-)-3PPP lacked any evidence of motor side effects. CONCLUSIONS: These data show that psychotic symptoms decrease with (-)-3PPP and suggest that the treatment of schizophrenia with partial dopamine agonist is a promising strategy. Future attention will be directed toward testing techniques to diminish the tachyphylaxis to allow an ongoing therapeutic effect.

Pharmacological profile of the antidepressant adinazolam, a triazolobenzodiazepine.

Adinazolam, which is a 1-dimethylaminomethyl triazolobenzodiazepine, is an effective anxiolytic agent as defined by suppression of stress-induced increases in plasma corticosteroids. Adinazolam is also an effective antagonist of pentylenetetrazole. The 1-dimethylaminoethyl triazolo analog, U-43,465F, was inactive in the stressed rat test and only weakly active against pentylenetetrazole. Adinazolam and U-43,465F have been previously shown to have antidepressant activity in classical screening tests. They have also been found to potentiate the effect of norepinephrine and this is consistent with the activity of the known antidepressants; U-43,465F was found to be equieffective to imipramine in this test. Adinazolam was also effective; however, the magnitude of the potentiation was not as great. The uptake of norepinephrine was only weakly affected by either compound. Potentiation or uptake of serotonin were not significantly-altered pharmacological factors. Receptor binding studies were negative except at the benzodiazepine receptor. Chronic treatment with adinazolam did not decrease the number of beta-adrenergic receptors in the cerebral cortex of the rat, in contrast to the positive effect of imipramine. The discovery of triazolobenzodiazepines with antidepressant activity is of special interest. These agents will hopefully have lower toxicity than the tricyclic antidepressants and thus possess a more favourable therapeutic index. This would be advantageous in the treatment of depression.

Conversion of N-alkylaminobenzophenones to benzodiazepines in vivo.

The results of this study suggest that 5-chloro-2-[3-methyl-5-(dimethylamino)methyltriazol-4-yl]benzophenone can undergo N-dealkylation and ring closure in vivo to form the corresponding benzodiazepine. The in vivo conversion was found to occur in mice, rats, and monkeys. A variety of substituted aminobenzophenone compounds were also able to undergo these conversions. The conversions to benzodiazepines were confirmed by a comparison of retention times on a gas chromatograph as well as through the use of a GC-mass spectrometer. The results obtained did not prove that the N-alkylaminobenzophenones were devoid of activity, but they do suggest that their observed pharmacological activity may be due to the formation of the corresponding benzodiazepines.

Factors affecting binding of trans-N-[2-(methylamino)cyclohexyl]benzamides at the primary morphine receptor.

In this paper, we describe the synthesis of a series of trans-N-[2-(methylamino)cyclohexyl]benzamides possessing morphine-like pharmacological properties. The affinity of the compounds for the agonist and antagonist states of the mu opioid receptor has been established by means of an in vitro binding assay. We have investigated the geometry and electronic structure of the molecules using molecular mechanics and an ab initio SCF-MO procedure with FSGO basis sets. Comparison to naloxone reveals properties of possible importance in receptor association. We have considered both the S,S and R,R isomers in the binding model. Statistical analyses imply that three factors play a significant role in binding: (1) membrane-water partitioning, (2) the capacity of the aromatic ring and amine N-substituent to act as electron acceptors, (3) the conformational energy required to attain the binding configuration.

Synthesis and pharmacology of novel anxiolytic agents derived from 2-[(dialkylamino)methyl-4H-triazol-4-yl] benzophenones and related heterocyclic benzophenones.

A series of novel [(dialkylamino)methyl-4H-1,2,4-triazol-4-yl]benzophenones and related compounds has been prepared via total synthesis from substituted aminodiphenylmethanes or by hydrolysis and subsequent methylation of triazolobenzodiazepines. These new triazole compounds were found to have potent sedative and muscle relaxing activity in mice (i.e., these compounds depressed the traction and dish reflexes). In addition, the title compounds antagonized the clonic convulsions induced in mice by the administration of pentylenetratrazole (Metrazol, 85 mg/kg), with ED50's varying from 2.0 to 23.0 mg/kg, and the lethality induced by thiosemicarbazide, with ED50's varying from 0.02 to 9.0 mg/kg. In several biological tests, the potency of seven new benzophenone derivatives approached or exceed that of diazepam (35a) or its glycylaminobenzophenone analogue 36.

Comparison of 5-HT1A and dopamine D2 pharmacophores. X-ray structures and affinities of conformationally constrained ligands.

Conformational and molecular mechanics studies of a new series of tricyclic ligands with affinity for either the dopamine D2 receptor or the 5-HT1A receptor, or both, has enabled us to elaborate considerably on previous pharmacophore models for these receptors. The new tricyclic ligands are either angular, 2,3,3a,4,5,9b-hexahydro-1H-benz[e]indole derivatives, or linear, 2,3,3a,4,5,9a-hexahydro-1H-benz[f]indole derivatives; they have either cis or trans ring junctions, and many of the ligands are resolved. In order to have X-ray crystal coordinates for every structural type, two additional crystal structures were determined: 14a, the trans-(+-)-6-hydroxy-3-(n-propyl) angular derivative as the hydrochloride, and (+-)-1,2,2a,3,4,8b-hexahydro-8-methoxy-2-(2-propenyl)-naphth[2,1- b]azetidine hydrochloride (16d). Several recently reported imidazoquinolinones with dopaminergic and serotonergic activities were also used in developing the models as were other known ligands which are conformationally constrained. A new method for determining intrinsic activity at the D2 receptor made consistent and reliable estimates of dopamine agonist, partial agonist, and antagonist activities available. The models explain these activities in terms of the 3-dimensional structural features of the ligands and their probable orientations at the D2 receptor site. They also explain why allyl and propyl analogs of some structures have very different affinities while affinities are quite similar for allyl and propyl analogs of other structures; at both receptors a particular orientation of the amine substituent in the binding site correlates with preference for allyl over propyl derivatives. Suggestions are made for enhancing selectivity at the 5-HT1A receptor or at the dopamine D2 receptor. An angular, cis, (3aR,9bS), 2-propyl, 9-hydroxy, 3-(n-propyl) analog should be selective for the 5-HT1A receptor. A linear, trans, (3aR,9aS), 7-hydroxy, 1-(2-propenyl) analog should be selective for the dopamine D2 receptor, and would be predicted to be an antagonist.

Novel anxiolytic agents derived from alpha-amino-alpha-phenyl-o-tolyl-4H-triazoles and -imidazoles.

Several new alpha-amino-alpha-phenyl-o-tolytriazoles and -imidazoles have been prepared in one step by means of a novel reductive rearrangement of the corresponding benzodiazepines with hydrazine hydrate. These new triazoles were found to have moderate sedative and muscle relaxing activity in mice (i.e., these compounds depressed the traction and dish reflexes at higher doses than did diazepam) but were very potent antagonists of the clonic convulsions induced in mice by the administration of pentylenetetrazole. Furthermore, they antagonized the lethality induced by thiosemicarbazide. While these new compounds were very active in mice, most were inactive in rats. These results are discussed with reference to the metabolism of compound 13.

Novel indolodioxanes with antihypertensive effects: potent ligands for the 5-HT1A receptor.

The synthesis and biological evaluation of a new family of tricyclic indolodioxanes is described. These compounds all contain the 2,3-dihydro-7H-1,4-dioxino[2,3-e]indole nucleus and bear substituents at the 2 and/or 8 positions. Thirteen members of this class were prepared and shown to be potent ligands for the 5-HT1A receptor, with several compounds displaying subnanomolar inhibition constants. These compounds also bind to the dopamine D-2 receptor, but generally with higher inhibition constants than those for 5-HT1A. Certain members of this novel structural class show in vivo activity in the mouse hypothermia assay. One of these compounds, U-86192A, has been shown to have antihypertensive effects in the cat, completely eliminating sympathetic nerve discharge at 1 mg/kg iv and lowering mean arterial pressure to 50% pretreatment levels. These effects can be reversed by the administration of spiperone, indicating that U-86192A is acting via a central serotonergic mechanism.

Centrally acting serotonergic agents. Synthesis and structure-activity relationships of C-1- or C-3-substituted derivatives of 8-hydroxy-2-(di-n-propylamino)tetralin.

The synthesis and structure-activity relationships (SAR) of C-1- or C-3-substituted derivatives of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) are described. These analogs were synthesized via alkylation of the tetralone derivatives followed by reductive amination. All of the analogs were inactive at the dopamine D2 receptor. Among the 8-OMe or 8-OH C-1,N-disubstituted analogs synthesized, the cis analogs were more potent in the 5-HT1A binding assay than the corresponding trans analogs. However, in the case of 1-(cyclopropylmethyl)-N-n-propyl analogs, the trans isomer has a slightly higher 5-HT1A affinity than its cis counterpart. The order of binding potency for C-1 substitution was found to be allyl > hydroxymethyl > n-propyl > cyclopropylmethyl >> carbomethoxy. Interestingly, the 5-OMe analogs were found to be inactive in both the 5-HT1A and dopamine D2 binding assays. In the C-3 allyl-substituted analogs, 5-HT1A agonist activity was found to be considerably lower. In these examples, the trans analogs showed weak 5-HT1A binding activity whereas the cis analogs were inactive. Analogs with C-1,N,N-trisubstitution also showed a marked decrease in 5-HT1A binding affinity. Overall, the SAR study showed that cis C-1 substitution maintains the 5-HT1A agonist activity of 8-OH-DPAT whereas trans C-1 substitution displays somewhat diminished activity. On the other hand, the trans C-3 substitution shows modest agonist activity whereas cis C-3 substitution removes the activity completely.

Naphtho and benzo analogues of the kappa opioid agonist trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide.

Further elaboration on the structure-activity relationships in our U-50,488 series has revealed that benzologation of this cyclohexane-1,2-diamine derivative provides compounds which either maintain the interaction with the kappa receptor (e.g. compounds 3a and 5a in the phenylacetamido series) or eliminate the mu receptor mediated analgesia (e.g. compounds 3-6 in the benzamido series). Naphthologation also caused the elimination of mu receptor mediated analgesia (e.g. compounds 17a and 17b).

Centrally acting serotonergic and dopaminergic agents. 1. Synthesis and structure-activity relationships of 2,3,3a,4,5,9b-hexahydro-1H-benz[e]indole derivatives.

The synthesis and structure-activity relationships (SAR) of 2,3,3a,4,5,9b-hexahydro-1H-benz[e]indole derivatives (3) are described. These compounds are conformationally restricted, angular tricyclic analogs of 2-aminotetralin. The synthesis was achieved in several steps from the corresponding 2-tetralones. The enantiomers of the cis analogs were obtained from either fractional recrystallizations of the diastereomeric salts of di-p-toluoyl-L-(or D)-tartaric acid or an asymmetric synthesis using chiral (R)-alpha-methylbenzylamine. All analogs were evaluated in the in vitro 5-HT1A and D2 binding assays and selected analogs were investigated further in biochemical and behavioral tests. Analogs with 9-methoxy substitution (R1 in 3) showed mixed 5-HT1A agonist and dopamine antagonist activities whereas the corresponding 9-hydroxy analogs displayed selective 5-HT1A agonist activity. The cis analogs were found to be more potent than the corresponding trans analogs and in the cis series, the (3aR)-(-)-enantiomers displayed higher potency. Nitrogen substitution (R2 in 3) with either an n-propyl or an allyl group produced similar activities whereas replacement with a bulky alpha-methylbenzyl group resulted in loss of activity. Analogs without aromatic substitution (R1 = H in 3) still showed good 5-HT1A agonist activity, although less potent than the 9-methoxy series. In this case, the trans analogs possessed equal or higher in vitro 5-HT1A affinity than the corresponding cis analogs. Analogs with either 6-methoxy or 6-hydroxy substitution (R1 in 3) were found to display dopamine antagonist properties. However, only N-allyl analogs showed this activity. In the 6-methoxy-N-allyl series, the cis analog was found to be more potent than the trans analog. Again, between the pair of cis enantiomers, the (3aR)-(-)-enantiomer showed higher potency. Incorporation of an additional methyl group into 9-methoxy cis analogs at C-2 resulted in retention of potent 5-HT1A agonist activity.

Centrally acting serotonergic and dopaminergic agents. 2. Synthesis and structure-activity relationships of 2,3,3a,4,9,9a-hexahydro-1H-benz[f]indole derivatives.

The conformationally restricted linear tricyclic analogs of 5- and 8-hydroxy-2-(di-n-propylamino)-tetralins were investigated for their serotonergic and dopaminergic properties. These cis and trans analogs of 2,3,3a,4,9,9a-hexahydro-1H-benz[f]indole (3), where a five-membered ring is fused between the nitrogen and C-3 carbon of 2-aminotetralin, were synthesized from 5-methoxy- and 8-methoxytetralones. The enantiomers of trans-5-methoxy-N-n-propyl and -N-allyl analogs were obtained via fractional recrystallization of their di-p-toluoyl-L (or D) tartaric acid salts. All analogs were evaluated in the in vitro 5-HT1A and D2 binding assays and selected analogs were investigated further in biochemical and behavioral tests. In the 5-substituted series (R1 in 3), the trans isomers were found to possess higher levels of pharmacological activity then the corresponding cis isomers. The trans-5-methoxy analogs showed selective 5-HT1A receptor activity in vitro but displayed mixed 5-HT1A and D2 agonist properties in vivo. The corresponding trans-5-hydroxy analogs were found to be potent D2 agonists with full intrinsic activity. An examination of nitrogen substitution (R2 in 3) revealed that analogs with either an allyl or an n-propyl group displayed equipotent activities. Substitution with a cyclopropylmethyl or benzyl group resulted in reduced activity. Among the resolved analogs tested, the activity was found to reside exclusively in the (3aS)-(-)-enantiomers. In the 8-substituted series (R1 in 3), only 8-methoxy-N-allyl analogs were synthesized and evaluated. In this case, both cis and trans isomers showed equally weak in vitro 5-HT1A receptor agonist activity devoid of dopaminergic effects. The presence of an additional methyl group at the C-2 position (R3 in 3) of the cis-(+/-)-8-methoxy-N-n-propyl analog resulted in enhancement of in vitro 5-HT1A receptor binding affinity, with the (2 beta,3a alpha,9a alpha)-(+/-)-isomer displaying potency 35 times greater than the (2 alpha,3a alpha,9a alpha)-(+/-)-isomer.

D2-family receptor distribution in human postmortem tissue: an autoradiographic study.

The distribution throughout the normal human brain of the dopamine D2-family of receptors were investigated autoradiographically. Three ligands were used, [3H]-YM-09151-2 to define the D2, D3, D4 receptors; [3H]raclopride the D2 D3 receptors; and [3H](+)-7-OH-DPAT, in the presence of GTP, demonstrates D3 distribution. [3H]-YM-09151-2 and [3H]raclopride binding were highest in caudate (121 vs 130 fmol mg(-1)), putamen (96 vs 136 fmol mg(-1)), and nucleus accumbens (113 vs 120 fmol mg(-1)). [3H]-YM-09151-2 also displayed significant binding in several cortical areas (56-39 fmol mg(-1)) and hippocampus (27 fmol mg-1). [3H](+)-7-OH-DPAT was highest in the nucleus accumbens. Based upon the ligands properties it is inferred that D2 distribution is highest in putamen, caudate and nucleus accumbens; D3 in the nucleus accumbens; D4 receptor in cortical areas and hippocampus.

D2-type dopamine receptors in postmortem human brain sections from normal and schizophrenic subjects.

The density of the presumed dopamine D4 receptor ([3H]YM-09151-2 minus [3H]raclopride), as well as the densities of the two ligands themselves were compared in various areas of cerebral tissue from normal versus schizophrenic subjects off or on antipsychotic drugs at the time of death. Using autoradiographic techniques, and analyzing various brain areas, no differences were found in the density of the D4 receptor, nor were differences found between the groups, in any brain region, in the amount of bound [3H]YM-09151-2 or [3H]raclopride. There were, therefore, no differences in the density of the D3-type receptors, including the D4 receptor, in normal and schizophrenic subjects off or on antipsychotic drugs at the time of death.

Evaluation of naloxone for therapy of Escherichia coli shock. Species differences.

Dogs and baboons were infused intravenously (IV) with Escherichia coli and treated with the opiate antagonist, naloxone hydrochloride, and the antibiotic, gentamicin sulfate, to determine the therapeutic efficacy of naloxone. Naloxone hydrochloride (2 mg/kg) was injected IV when one fourth of the E coli had been infused and then infused at 2 mg/kg/hr (six hours for dogs and 12 hours for baboons). Four of five naloxone-treated dogs survived permanently (greater than seven days), while all dogs that were given only E coli died. Arterial BP, blood glucose levels, PCO2, and PO2 were supported at higher levels and lesions of the gastrointestinal tract were prevented in naloxone-treated dogs. A steady decline in blood glucose levels after an initial hyperglycemia was observed in naloxone-treated baboons, indications of peripheral vasoconstriction were noted, and all baboons died within 42 hours.

3H-SKF10047 receptor binding studies. Attempts to define the opioid sigma receptor.

The results of experiments are described in which attempts have been made to use the multi-site ligand (d,l)3H-SKF10047 to define a binding site that may be the opioid sigma site. This was attempted by using highly selective blocking agents to eliminate binding at the other opioid sites. The remaining bound 3H-SKF10047, approximately 20% of total specific bound, was then characterized using competitive binding studies with different types of opioids. Under these conditions, a binding site was identified which is highly selective for the benzmorphans and certain morphinans known to cause dysphoria. The kappa selective agent (l)U-50488 did not demonstrate high activity for this site and neither did several mu opioids, PCP or the (d) enantiomers of two opioid benzmorphans. The carefully defined site may be the putative opioid sigma receptor.

Growth of Chinese hamster ovary (CHO) cells expressing the 5-HT2 serotonin receptor in suspension culture: an efficient method for large-scale acquisition of membrane protein for drug evaluation.

Chinese hamster ovary (CHO) cells expressing the rat 5-HT2 serotonin receptor were grown and evaluated in suspension culture to provide an efficient method of producing membrane-bound receptors for drug discovery. Expression of the 5-HT2 receptor in cells grown in batch suspension culture fluctuated as a function of culture age. Both receptor expression and receptor G-protein coupling were the highest early (1.9 pmol/mg membrane protein) but declined rapidly as the culture increased in age. However, addition of fresh serum-containing medium to stationary-phase cells reversed the decline and, after 24 h of growth, resulted in maximal receptor density and G-protein coupling. This serum response was found to be reproducible and lead to the establishment of a semi-continuous batch culture system in which cells were maintained in a growth state that supported high levels of membrane-incorporated and G protein-coupled receptors. In this system, 50% of the culture volume could be removed at 24-h intervals for membrane preparation and the lost volume replenished with fresh medium, resulting in a continuous supply of high-quality membrane preparations.

Drug affinities for the agonist and antagonist states of the opioid receptor.

Traditional methods of analyzing the binding of opiates do not accurately establish the affinities of the drugs for the agonist and antagonist states of the opioid receptor. The poor results obtained by the Scatchard procedure may be attributed to the presence of extraneous drug binding sites in the brain-homogenate medium. In this study a nonlinear regression technique has been employed to analyze receptor binding in terms of the two-state Snyder-Pert model while simultaneously considering drug association with the aggregate of non-receptor binding sites. Results are reported for naloxone, pentazocine, and dihydromorphine, which respectively represent a pure antagonist, a mixed agonist-antagonist, and a pure agonist. the affinity constants characterizing equilibrium binding at the agonist and antagonist states of the receptor at 37 degrees C are given for each of the three drugs. In addition, a theoretical index, f tau, is defined which provides a measure of the fraction of receptors existing in the agonist state. It is found that the graft of f tau vs log [D] exhibits features similar to the in vivo dose-response curves for the drugs.

Des-tyrosine1-gamma-endorphin increases the antinociceptive efficacy of morphine in the rat.

Repeated injections of des-tyrosine1-gamma-endorphin (DT gamma E) to rats subjectively increased sensitivity to handling. After 8 days of treatment, the animals were supersensitive to a low dose of morphine in the foot-shock test. Acute treatment with DT gamma E gave no significant increase in morphine sensitivity. The results indicate that DTgammaE given chronically interacts with opioid receptor-effector mechanisms.