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The results of the present study show that the down-regulation of beta-adrenoceptors of rat brain, induced by subacute administration of sertraline, is facilitated when this selective serotonin reuptake inhibitor was co-administered with the serotonin releaser, norfenfluramine, or the serotonin terminal autoreceptor antagonist, methiothepin. The respective drug combination produced a reduction in Bmax of [3H]dihydroalprenolol binding to cortical membranes of treated rats at a dose of the releaser, release enhancer, or sertraline, which was ineffective when administered alone. In a similar manner, the 5-HT1A agonists, gepirone and 8-OH-DPAT, were found to facilitate the downregulation of beta-adrenoceptors induced by sertraline. The 5-HT1B agonist, 3-trifluoromethylphenylpiperazine, and the 5-HT2 antagonist, ritanserin, showed neither facilitation nor antagonism of sertraline, but the 5-HT3 antagonist, ondansetron, attenuated the decrease of Bmax of [3H]dihydroalprenolol binding elicited by sertraline. Agents that putatively increase the serotoninergic activity facilitated the down-regulation of beta-adrenoceptors induced by sertraline, suggesting that the enhancement of serotonin transmission, expected of the selective serotonin reuptake inhibitor itself, may play a role in this effect of sertraline. Whether the downregulation of brain beta-adrenoceptors by sertraline plays any role in its antidepressant activity cannot be deduced from these experiments.

A series of rotationally restricted phenolic analogs of the neurotransmitter serotonin has been synthesized with the 5-hydroxyindole portion of serotonin replaced by a dihydropyrano[3,2-e]-indole (1, 3, 4, and 5) and a dihydropyrano[2,3-f]indole (2). The receptor binding profile of these compounds has been studied and compared to the natural substrate serotonin. The dihydropyrano[3,2-e]indole derivatives (1, 3, 4, and 5) possess lower affinity for 5-HT1 receptors but equal or greater affinity for 5-HT2 receptors. Like serotonin, these compounds dose-dependently stimulated phosphatidylinositol turnover in rat brain slices. Moreover, the response to 1-(2-aminoethyl)-3-methyl-8,9-dihydropyrano[3,2-]indole (5, CP-132,484) and 1-(2-aminoethyl)-8,9-dihydropyrano[3,2-e]indole (4) is selectively antagonized by 5-HT2 receptor antagonists establishing these tryptamines as selective 5-HT2 receptor agonists. The high affinity and potency of 5 for 5-HT2 receptors suggests that the C5-hydroxy group in serotonin can function as a hydrogen bond acceptor in a 5-HT2 receptor with a directionality of interaction which is down and away from C6 in serotonin (Figure 5). Furthermore, the potent affinity of these compounds for 5-HT2 receptors coupled with their poor affinity for 5-HT1 receptors indicates that the aminoethyl side chain of serotonin adopts significantly different conformations in 5-HT1 versus 5-HT2 receptors.

3-(1,2,5,6-Tetrahydro-4-pyridyl)-5-n-propoxyindole (CP-96,501) was found to be more selective ligand at the serotonin 5-HT1B receptor than the commonly used 5-HT1B agonist, 3-(1,2,5,6-tetrahydro-4-pyridyl)-5-methoxyindole (RU 24969). In rat brain membranes, the tritiated derivative, [3H]CP-96,501, was found to bind with a high affinity (KD, 0.21 nM) to a single binding site (nH, 1.0). The receptor density of this site (Bmax, 72 fmol/mg of protein) matched that of the 5-HT1B receptor determined with [3H]5-HT. Competition curves of 16 serotonergic compounds in [3H]CP-96,501 binding also indicated a single binding site. The rank order of their binding affinities with this new radioligand showed a high degree of correlation with their affinities at the 5-HT1B receptor determined with [3H]5-HT or [125I]iodocyanopindolol. Serotonergic compounds displayed competitive inhibition of [3H]CP-96,501 binding. In the presence of 5'-guanylylimidodiphosphate [Gpp(NH)p], [3H]CP-96,501 to displace [125I]iodocyanopindolol binding was also decreased. These findings are consistent with the agonist nature of CP-96,501. The results of this study suggest that [3H]CP-96,501 is a useful agonist radioligand for the 5-HT1B receptor.

Ifenprodil (1) represents a new class of N-methyl-D-aspartate (NMDA) antagonist. This drug also possesses potent activity at several other brain receptors (most notably alpha 1 adrenergic receptors). We have prepared the enantiomers and diastereomers of ifenprodil along with a series of partial structures in order to explore the basic structure activity relations within this class of compounds. From this study, it is clear that alpha 1 adrenergic and NMDA receptor activities may be separated by selection of the threo relative stereochemistry. Examination of the optical isomers of threo-ifenprodil (2) reveals that no further improvement in receptor selectivity is gained from either antipode. Individual removal of most of the structural fragments from the ifenprodil molecule generally results in less active compounds although fluorinated derivative 9 with threo relative stereochemistry is somewhat more potent and substantially more selective for the NMDA receptor. Finally a minimum structure for activity in this series (14) has been identified. This stripped-down version of ifenprodil possesses nearly equivalent affinity for the NMDA receptor with no selectivity over alpha 1 adrenergic receptors.

A series of quinazolinediones and azaquinazolinediones is described which possess potent inhibitory activity toward the calcium-independent phosphodiesterase enzyme (CaIPDE). In vivo testing showed that this in vitro activity translates to animal models predictive of chronic diseases such as depression and inflammation. These results support the hypothesis that inhibition of CaIPDE may lead to useful activity in such chronic diseases.

The synthesis and biological properties of a novel series of selective calcium-independent phosphodiesterase inhibitors are described. These compounds also inhibit the specific binding of [3H]rolipram to rat brain membranes and exhibit efficacy in preclinical models of antidepressant activity in mice, such as reducing immobility in the forced-swim test and reversing reserpine-induced hypothermia. Imidazolidinones 4 and 16 were found to be the most potent compounds studied.

The synthesis and biological properties of a series of nicotinamide ethers are described. These compounds, structurally novel calcium-independent phosphodiesterase inhibitors, also inhibit the binding of [3H]rolipram to rat brain membranes and reverse reserpine-induced hypothermia in the mouse. Several compounds exhibited potent in vivo activity comparable to the standard agent, rolipram.

Specific serotonin reuptake inhibitors constitute a new class of psychotherapeutic agents that promote enhanced central serotonergic neurotransmission in animal studies. Sertraline, a member of this class, exhibits considerable potency and specificity in inhibiting serotonin neuronal reuptake in preclinical studies. Thus, it is likely to exert antidepressant activity without significant anticholinergic, cardiovascular, and sedative side effects. Other animal studies demonstrating decreases in food intake and body weight and reduction in voluntary alcohol consumption after sertraline administration suggest a potential for wider clinical application.

A series of 4-amino[1,2,4]triazolo[4,3-a]quinoxalines has been prepared. Many compounds from this class reduce immobility in Porsolt's behavioral despair model in rats upon acute administration and may therefore have therapeutic potential as novel and rapid acting antidepressant agents. Optimal activity in this test is associated with hydrogen, CF3, or small alkyl groups in the 1-position, with NH2, NH-acetyl, or amines substituted with small alkyl groups in the 4-position, and with hydrogen or 8-halogen substituents in the aromatic ring. Furthermore, many of these 4-amino[1,2,4]triazolo[4,3-a]quinoxalines bind avidly, and in some cases very selectively, to adenosine A1 and A2 receptors. A1 affinity of these compounds was measured by their inhibition of tritiated CHA (N6-cyclohexyladenosine) binding in rat cerebral cortex membranes and A2 affinity by their inhibition of tritiated NECA (5'-(N-ethylcarbamoyl)adenosine) binding to rat striatal homogenate in the presence of cold N6-cyclopentyladenosine. Structure-activity relationship (SAR) studies show that best A1 affinity is associated with ethyl, CF3, or C2F5 in the 1-position, NH-iPr or NH-cycloalkyl in the 4-position, and with an 8-chloro substituent. Affinity at the A2 receptor is mostly dependent on the presence of an NH2 group in the 4-position and is enhanced by phenyl, CF3, or ethyl in the 1-position. The most selective A1 ligand by a factor of greater than 3000 is 121 (CP-68,247; 8-chloro-4-(cyclohexyl-amino)-1- (trifluoromethyl)[1,2,4]triazolo[4,3-a]quinoxaline) with an IC50 of 28 nM at the A1 receptor. The most potent A2 ligand is 128 (CP-66,713; 4-amino-8-chloro-1- phenyl[1,2,4]triazolo[4,3-a]quinoxaline) with an IC50 of 21 nM at the A2 receptor and a 13-fold selectivity for this receptor. Representatives from this series appear to act as antagonists at both A1 and A2 receptors since they antagonize the inhibiting action of CHA on norepinephrine-stimulated cAMP formation in fat cells and they decrease cAMP accumulation induced by adenosine in limbic forebrain slices. Thus certain members of this 4-amino[1,2,4]triazolo[4,3-a]quinoxaline series are among the most potent and A1 or A2 selective non-xanthine adenosine antagonists known.

Tritiated sertraline, a radiolabeled form of a potent and selective inhibitor of serotonin uptake, was found to bind with high affinity to rat whole brain membranes. Characterization studies showed that [3H] sertraline binding occurred at a single site with the following parameters: KD 0.57 nM, Bmax 821 fmol/mg protein, nH 1.06. This binding was reversible; the dissociation constant calculated from kinetic measurements (KD 0.81 nM) agreed with that determined by saturation binding experiments. [3H] Sertraline binding in the presence of serotonin, paroxetine, fluoxetine or imipramine suggested competitive inhibition of binding (large increase in KD with little change in Bmax). The rank order of potency of inhibition of [3H] sertraline binding was similar to that of inhibition of serotonin uptake for known uptake inhibitors and the 1-amino-4-phenyltetralin uptake blockers. A marked decrease in ex vivo [3H] sertraline binding in the brain of rats 7 days after treatment with p-chloroamphetamine was consistent with the loss of serotonin uptake sites induced by this agent. The results of our study indicated that [3H] sertraline labels serotonin uptake sites in rat brain.

Levonantradol antagonized the compensatory acceleration of striatal dopamine synthesis induced by haloperidol. This effect was stereospecific, since the pharmacologically less active enantiomer, dextronantradol was approximately 30 times less effective. delta 9-Tetrahydrocannabinol at a dose 320 times higher than levonantradol also attenuated the haloperidol effect, but cannabidiol was inactive at a dose 750 times higher. GABA-like actions of levonantradol may be responsible for this responsible for this antagonism of haloperidol, but anticholinergic effects may also contribute.

Sertraline [1S,4S-N-methyl-4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-naphthylamine] was found to be a highly selective and potent competitive inhibitor of synaptosomal serotonin uptake. Sertraline also selectively reduced ex vivo uptake of serotonin and strongly antagonized the serotonin-depleting action of p-chloroamphetamine, indicating potent blockade of serotonin uptake in vivo. Acute and repeated dosing of sertraline decreased serotonin content of whole blood. Sertraline only weakly inhibited rat heart uptake of i.v. [3H]norepinephrine. In substantiation of selective blockade of serotonin uptake, sertraline potentiated various symptoms of 5-hydroxytryptophan but did not reverse reserpine-induced hypothermia. Sertraline was a very weak inhibitor of [3H]quinuclidinyl benzilate binding to rat brain membranes in vitro and did not produce anticholinergic effects in mice in vivo. Sertraline was well tolerated in mice, rats and dogs, with no locomotor stimulant effects in rats or untoward cardiovascular effects in dogs. The major metabolite, N-demethylsertraline, was also a selective serotonin uptake blocker. Sertraline strongly reduced immobility of mice in the Porsolt swim test for antidepressants. After repeated dosing in rats, sertraline diminished the cyclic AMP response of limbic forebrain adenylate cyclase to norepinephrine, as well as the binding of [3H]dihydroalprenolol to cortical membranes. It is proposed that selective blockade of serotonin reuptake can induce activation of norepinephrine neurons and subsequent down-regulation of norepinephrine receptors and that sertraline, a highly selective inhibitor of serotonin uptake, may be an efficacious antidepressant without anticholinergic or cardiovascular side-effects.

In an attempt to enhance the potency of the dopamine autoreceptor agonist 3-PPP, racemic cis-3-(3-hydroxyphenyl)-5-[(methylmercapto)methyl]-N-n-propylpiperidine has been prepared in a stereoselective synthesis. NMR studies of 3 show a diequatorial conformation for the 3- and 5-substituents, which gives compound 3 an intriguing overlap with the ergoline derivative pergolide. Pharmacological testing revealed that 3, which is a 5-(methylmercapto)methyl derivative of racemic 3-PPP does not show the anticipated potency increase as a dopamine autoreceptor agonist. In vitro (inhibition of tyrosine hydroxylation) 3 and 1 have similar potency, and the in vivo potency (inhibition of GBL accelerated dopamine synthesis) of 3 is inferior to that of 1.

Imidoline, 1-[2-(N,N-dimethylamino)ethyl]-3-m-chlorophenyl-2-imidazolidinone, has been found to be as potent as chlorpromazine in increasing striatal DOPA accumulation and prolactin secretion in vivo. In contrast, imidoline exhibited only weak inhibitory activity towards dopamine-sensitive adenylate cyclase and 3H-spiroperidol binding to striatal membranes in vitro. These neuroleptic effects in vivo are probably caused by blockade of dopamine receptors since imidoline did not deplete the striatum of dopamine. Imidoline is of interest because its structure is distinct from those of other neuroleptics. A proposed active conformation involves intramolecular hydrogen bonding between the protonated dimethylamino group and the oxygen of the imidazolidinone ring. The spatial relationship between the amine nitrogen and phenyl ring in this conformation allows proper fit of imidoline with key dimensions described for the dopamine receptor.

The agonist actions of 3-PPP at central dopamine (DA) autoreceptors were found to reside mostly in its (+) enantiomer, (+)-3-PPP also reduced striatal content of DOPAC and HVA, whereas (-)-3-PPP elevated HVA levels. Only (-)-3-PPP antagonized DA stimulation of DA-receptor linked adenylate cyclase. It was more effective than (+)-3-PPP at inhibiting [3H]DA binding to striatal membranes. The results suggest that (+)-3-PPP may act predominantly at DA autoreceptors, while (-)-3-PPP exhibits weak affinity for presynaptic and postsynaptic DA receptors.

Sertraline is a member of a new class of psychotherapeutic agents that selectively inhibit serotonin reuptake in the brain. Animal studies have demonstrated that inhibition of serotonin reuptake leads to enhanced serotonergic neurotransmission and indirectly results in a down-regulation of beta-adrenoceptors. The preclinical pharmacology of sertraline predicts antidepressant activity without accompanying anticholinergic, cardiotonic, or sedative side effects. Recent laboratory and clinical observations pertaining to body weight and obsessive compulsive disorder suggest the possibility of broader clinical indications for selective serotonin reuptake blockers such as sertraline.

Serotonin uptake blockers have been shown to produce a robust and reliable reduction in voluntary ethanol consumption in rats. These compounds are currently under investigation as potential treatments for alcohol abuse in humans. It is uncertain whether serotonin uptake blockers exert their effects directly through serotonergic mechanisms or whether an interaction between the serotonin and noradrenergic systems is involved. The present series of experiments was designed to examine the effects of sertraline, a new selective serotonin uptake blocker, on voluntary ethanol intake. Sertraline produced a robust reduction in voluntary ethanol intake. It appears therefore, that increasing selectivity for serotonin blockade does not alter the efficacy of these compounds as antialcohol agents. The drug also reduced the consumption of a saccharin solution indicating that sertraline's effects are not specific to ethanol intake.

Subacute administration (b.i.d. for 4 days) of sertraline, a potent and selective inhibitor of serotonin uptake, was found to reduce cyclic AMP generation by the norepinephrine receptor-coupled adenylate cyclase in rat limbic forebrain slices and decrease the number of beta-adrenoceptors in rat cerebral cortex without affecting the affinity of [3H]dihydroalprenolol binding. Co-administration of sertraline and the serotonin agonist, quipazine, at doses at which neither agent had an effect, resulted in desensitization of norepinephrine receptor-coupled adenylate cyclase and down-regulation of beta-adrenoceptors. These findings suggest that increased serotonergic activity may be involved in the induction of subsensitivity of the beta-adrenoceptor system of rat brain by sertraline.

Ethyl beta-carboline-3-carboxylate (beta CCE), a benzodiazepine antagonist, was found to increase basal levels of cyclic GMP in rat cerebellum. beta CCE also augmented the elevation of cyclic GMP concentrations induced by isoniazid, in contrast to diazepam which blocked this effect of isoniazid. Administration of beta CCE and diazepam together cancelled each other's effect on the elevation of cyclic GMP levels after isoniazid. Ro 15-1788, another potent benzodiazepine antagonist, was found to have virtually no effect on cyclic GMP levels in naive or isoniazid-treated rats. Ro 15-1788 antagonized diazepam's lowering of the elevation of cyclic GMP content of cerebellum after isoniazid. Ro 15-1788 also blocked the increase in cyclic GMP levels elicited by beta CCE, indicating that this effect of beta CCE involves its interaction at benzodiazepine receptors. Some pharmacological actions of beta CCE might be based on hindering GABA transmission.

A series of 5-aryltetrahydro-gamma-carbolines was prepared by a novel N-arylation procedure and tested for neuroleptic activity in a rat antiamphetamine model. The systematic exploration of structural parameters leading to 8-fluoro-5-(4-fluorophenyl)-2-[4-hydroxy-4-(4-fluorophenyl)butyl]-2,3,5-tetrahydro-1H-pyrido[4,3-b]indole (CP-36,584, flutroline), a potent and long-acting neuroleptic compound, is described. These semirigid compounds provide a new, structurally distinct series with which to probe the conformational requirements for potent activity at the dopamine receptor.

Antagonism of mercaptopropionic acid (MPA) induced convulsions, reflecting a GABAergic mechanism, was observed in a series of 1-aryl-3-(aminoalkylidene)oxindoles. Optimal MPA antagonism was associated with 3-halo, 3-alkyl, and/or 4-alkoxy substituents in the pendant aryl ring and with (dimethylamino)methylene, 1-(dimethylamino)-ethylidene and N-methyl-2-pyrrolidinylidene side chains. The precise mechanism of action of these agents is unclear at this time; however, they are not GABA mimics and they do not affect GABA levels. Like other GABAergic agents, these compounds are potent enhancers of benzodiazepine binding and they antagonize cyclic GMP elevations induced by isoniazid. Compounds from this series may therefore have potential therapeutic utility as anticonvulsants or anxiolytics.

A series of trans-8-fluoro-5-(4-fluorophenyl)-2,3,4,4a,5, 9b-hexahydro-1H-pyrido[4,3-b]indoles with various N-2 substituents has been prepared and tested for neuroleptic activity [( 3H]spiroperidol binding and amphetamine antagonism). Several members of this series showed exceptional in vivo potency, especially the hydantoin derivatives 27-30. Resolution into the enantiomers showed that neuroleptic activity is associated with the 4aS,9bS absolute configuration. These rigid neuroleptics have been correlated with other rigid neuroleptics [(+)-dexclamol, Ro 22-1319] and can serve to further define the topography of the dopamine receptor.

Substitution of position 2 of the 4a,9b-trans-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4,3-b]indole nucleus with omega-carboxamidoalkyl substituents leads to compounds with exceedingly potent neuroleptic activity in in vitro and in vivo models. Although duration of activity is not as long as that of the analogous 4-hydroxy-4-(4-fluorophenyl)butyl derivatives reported previously, the absolute potency in vivo is greater. The ability of these compounds to bind with great affinity to dopamine (DA) receptors further defines the nature of the DA receptor auxiliary binding site as a hydrogen-bond donating site in addition to or instead of a lipophilic site as has been previously proposed.

Administration of the benzodiazepine receptor antagonist, [3H]Ro 15-1788, to mice intravenously was found to label these receptors in brain. Binding of [3H]Ro 15-1788 in vivo was strongly blocked by pretreating mice with clonazepam or diazepam. Marked enhancement of [3H]Ro 15-1788 binding in vivo was induced by progabide or sodium valproate. This effect was greater than a similar enhancement of [3H]flunitrazepam binding. The increased membrane-bound [3H]Ro 15-1788 elicited by progabide was completely dissociated on subsequent incubation with Ro 15-1788, diazepam or clobazam, indicating that the enhanced binding occurred at benzodiazepine receptors. Compounds that exert diazepam-like actions and/or indirect GABAergic activity (cartazolate, pentobarbital, methaqualone, levonantradol, phenytoin) elicited enhancement of [3H]Ro 15-1788 in vivo. Other CNS agents (atypical neuroleptics, GABA antagonists, baclofen, some 5-HT1 agonists) also induced elevation of [3H]Ro 15-1788 binding in vivo, as did drugs exerting vasodilatatory effects (papaverine, nimodipine, verapamil, prazosin, N6-cyclohexyladenosine). Possible explanations for enhancement of [3H]Ro 15-1788 binding in vivo include increase in the number of benzodiazepine receptors induced by GABA or GABAergic drugs or effects of binding enhancers that elevate brain levels of [3H]Ro 15-1788, such as accelerating cerebral blood flow, competing for radioligand binding sites in plasma or increasing metabolic stability of the radioligand.

The interaction of levonantradol and its pharmacologically less active (+)-enantiomer with GABAergic mechanisms was studied in several in vivo systems: (1) rat cerebellar cGMP, based on the inverse relationship of GABAergic activity and cGMP levels; (2) convulsions elicited by 3-mercaptopropionic acid, an inhibitor of GABA synthesis; and (3) activated dopamine synthesis in rat striatum following blockade of dopamine receptors. Levonantradol decreased rat cerebellar cGMP content at low doses (1.0 mg/kg intraperitoneally) and antagonized elevation of cGMP levels by the GABA biosynthesis inhibitor isoniazid at even lower doses (0.32 mg/kg intraperitoneally); this activity pattern is suggestive of GABAergic activity. This conclusion is also supported by levonantradol's protection of mice against the convulsant effects of 3-mercaptopropionic acid, GABAergic agents are known to antagonize the enhanced dopamine synthesis and turnover that accompany dopamine receptor blockade by neuroleptics. Levonantradol (0.047 mg/kg intravenously) stereospecifically attenuated the elevated dopa accumulation induced by haloperidol. Levonantradol is at least 100-fold more active than THC in blocking isoniazid-induced elevation of cGMP levels in rat cerebellum or haloperidol-induced enhanced dopa accumulation in rat striatum.

Several compounds of relatively rigid molecular structure have been found to exert strong blockade of monoamine uptake by synaptosomal preparations of rat corpus striatum (dopamine and serotonin) and hypothalamus (norepinephrine). These include CP-24,441 (1R, 4S-N-methyl-4-phenyl-1,2,3,4-tetrahydro-1-naphthylamine), EXP-561 (4-phenylbicyclo[2.2.2]octan-1-amine), nomifensine and nefopam. The well-defined molecular geometry of the potent inhibitor EXP-561 is a fundamental structural/conformational requirement for uptake blocking activity for the large family of phenylbutylamine- and phenoxypropylamine-related inhibitors. The tubular configuration of EXP-561 may be the most appropriate for blocking serotonin uptake. The requisite conformation for blocking dopamine uptake appears to be defined by the combination resulting from superimposition of the CP-24,441 and nomifensine structures. The conformation defined by the combination resulting from superimposition of the CP-24-441 and desipramine structures is apparently optimal for blocking norepinephrine uptake. The conformational requirements for diphenylpropylamine-related uptake blockers may be defined by the rigid compound CP-39,332 (N-methyl-4-phenyl-1,2,3,4-tetrahydro-2-naphthylamine). The actual potency of any given inhibitor is probably modulated by additional structural and stereochemical factors.

The preparation and testing of the two racemic diastereoisomers and the four optically active enantiomers of the title compound in in vitro and in vivo models for determining potential antipsychotic activity are described. Both racemic diastereoisomers and two of the four chiral enantiomers are potent and long-acting neuroleptic compounds.

Levonantradol enhanced binding of 3H-diazepam to rat cortical membranes. Scatchard analysis of this effect showed apparent KD and Bmax changes at 100 microM levonantradol and a KD decrease at 50 microM. Dextronantradol caused a similar enhancement, suggesting a lack of stereospecificity in vitro. Subsequently, levonantradol at pharmacologic doses (0.15 mg/kg subcutaneously) was found to enhance the binding of intravenous 3H-flunitrazepam to mouse brain. In contrast to the results in vitro, dextronantradol showed no enhancement of 3H-flunitrazepam binding at doses up to 15 mg/kg subcutaneously. This stereospecific interaction with benzodiazepine receptors in vivo suggests that levonantradol may facilitate the pharmacologic actions of benzodiazepines. Levonantradol, at doses of 0.32 and 3.2 mg/kg subcutaneously, which did not block the convulsant effect of pentylenetetrazol, enhanced both the potency and efficacy of diazepam in elevating the absolute threshold of pentylenetetrazol for eliciting clonic seizures. Consistent with its lack of facilitation of benzodiazepine binding, dextronantradol at 3.2 mg/kg, a dose without effect on pentylenetetrazol-induced convulsions, showed little or no enhancement of diazepam's anticonvulsant activity against the latter.

The need for drugs that lack the obtrusive and limiting side effects of the tricyclic antidepressants has prompted the search for agents with greatly enhanced selectivity for specific mechanisms believed to be essential for antidepressant efficacy. The potential role of derangements of 5-HT pathways in the etiology of depression has long been suspected and has given impetus to the development of newer compounds that accentuate inhibition of serotonin reuptake. This paper presents structure-activity relationships for a series of cis-1-amino-4-(substituted-aryl)tetralins, which are surprisingly potent and selective inhibitors of serotonin uptake in in vitro models. These compounds are pharmacologically distinct from corresponding members of the trans series, which also potently block uptake of dopamine and norepinephrine. The activity in both cis and trans series is stereospecific, being restricted to the cis-(1S,4S) and the trans-(1R,4S) enantiomers.

Compounds derived from 4a,9b-trans-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4, 3-b]indole are consistently efficacious in displacing [3H]spiroperidol from striatal dopamine receptors in vitro. Derivatives bearing substituents at position 2, particularly those derived from butyrophenone moieties, are exceptionally potent in vivo. Compounds from the corresponding 4a,9b-cis series are substantially less potent in both in vivo and in vitro assays of neuroleptic activity. Although the cis and trans derivatives have, in some conformations, similar basic nitrogen atom to aromatic ring separations of about 5.1 A, the distance at which the basic nitrogen atom lies above or below the plane of the aromatic ring differs substantially between the two series. Consideration of these results in terms of this and earlier work indicates that the out-of-plane distance for the basic nitrogen in neuroleptic molecules may range from about 0 to about 0.90 A but may be optimized at about 0.55 A.

Novel, synthetic cannabimimetics and delta 9-tetrahydrocannabinol were found to enhance the binding of [3H]flunitrazepam to mouse brain in vivo. This property, suggestive of facilitation of binding to benzodiazepine receptors, is consistent with the potentiation of the anticonvulsant activity of diazepam against pentylenetetrazol by these compounds. The relative potencies of delta 9-tetrahydrocannabinol and the new cannabimimetics for enhancing [3H]flunitrazepam binding in vivo could also be correlated with their relative analgesic efficacies. Similar pharmacological stereospecificity was displayed for both binding enhancement and analgesic effects. The following order of decreasing potency was observed: N-methyllevonantradol and (-)-CP-55,244 greater than levonantradol, canbisol, CP-42,096 and (-)-CP-55,940 greater than 9-beta-normethyl-9-beta-hydroxyhexahydrocannabinol, nabilone and CP-47,497 greater than delta 9-tetrahydrocannabinol. Dextronantradol, (+)-CP-55,940 and (+)-CP-55,244 were considerably less active than the respective (-)-enantiomers; cannabidiol was inactive. Extensive investigation of structure versus activity led to N-methyllevonantradol and the 3-(2-hydroxyphenyl)cyclohexanols derivative, (-)-CP-55,244, which are approximately 1000-fold more potent than delta 9-tetrahydrocannabinol.

Binding of i.v. administered (+)-[3H]3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ([3H]3-PPP) in the brain of intact mice is antagonized dose responsively by sigma receptor ligands. The correlation of potencies for inhibition of binding in vivo and in vitro indicates that sigma receptors in mouse brain are labeled in vivo by i.v. [3H]3-PPP. 3-PPPP, the N-phenylpropyl derivative of norpropyl-3-PPP exhibits very high affinity for sigma receptors in vitro and in vivo.