Seroquel was compared to clozapine and several other antipsychotic agents in tests predictive of antipsychotic activity or extrapyramidal symptoms. In the conditioned avoidance test in squirrel monkeys as well as several paradigms using apomorphine or amphetamine-induced behavioral alterations, seroquel displayed the profile of a drug with potential antipsychotic activity. In these paradigms the potency of seroquel was somewhat less than clozapine in rodent tests, while the reverse was true in higher species, i.e. monkeys, cats. In tests designed to evaluate the propensity to induce EPS or tardive dyskinesia, for example, the production of dyskinetic reactions in haloperidol-sensitized cebus monkeys, seroquel displayed a profile similar to clozapine and disparate from typical antipsychotic drugs. In drug-naive cebus monkeys seroquel sensitized significantly fewer monkeys than haloperidol and the dyskinetic reactions were of significantly less intensity. It is anticipated that this novel antipsychotic agent will have a significantly reduced propensity to produce extrapyramidal symptoms and tardive dyskinesia than typical antipsychotics.

A great need exists for antipsychotic drugs which will not induce extrapyramidal symptoms (EPS) and tardive dyskinesias (TDs). These side effects are deemed to be a consequence of nonselective blockade of nigrostriatal and mesolimbic dopamine D2 receptors. Nondyskinetic clozapine (1) is a low-potency D2 dopamine receptor antagonist which appears to act selectively in the mesolimbic area. In this work dopamine antagonism was assessed in two mouse behavioral assays: antagonism of apomorphine-induced climbing and antagonism of apomorphine-induced disruption of swimming. The potential for the liability of dyskinesias was determined in haloperidol-sensitized Cebus monkeys. Initial examination of a few close cogeners of 1 enhanced confidence in the Cebus model as a predictor of dyskinetic potential. Considering dibenzazepines, 2 was not dyskinetic whereas 2a was dyskinetic. Among dibenzodiazepines, 1 did not induce dyskinesias whereas its N-2-(2-hydroxyethoxy)ethyl analogue 3 was dyskinetic. The emergence of such distinctions presented an opportunity. Thus, aromatic and N-substituted analogues of 6-(piperazin-1-yl)-11H-dibenz[b,e]azepines and 11-(piperazin-1-yl)dibenzo[b,f][1,4]thiazepines and -oxazepines were prepared and evaluated. 11-(4-[2-(2-Hydroxyethoxy)ethyl]piperazin-1-yl)dibenzo[b,f][1,4]thiazepine (23) was found to be an apomorphine antagonist comparable to clozapine. It was essentially nondyskinetic in the Cebus model. With 23 as a platform, a number of N-substituted analogues were found to be good apomorphine antagonists but all were dyskinetic.

1 Standard whole cell patch clamp recording techniques were used to study the pharmacological characteristics and site of econazole-mediated inhibition of calcium release-activated calcium current (Ic,_,)

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