Decreased antistereotypic effect of neuroliptics after additional treatment with a benzodiazepine, a GABA agonist or an anticholinergic compound.

Neuroleptics are very potent antagonists against stereotypies induced by DA-stimulants including methylphenidate. This effect of neuroleptics is usually related to the antipsychotic effect of these compounds. In contrast we found that GABA agonists potentiate stereotyped gnawing induced by methylphenidate. The GABA agonist muscimol in combination with neuroleptics will attenuate the antagonistic effect of these compounds on stereotyped gnawing induced by methylphenidate. However a differentiation between the neuroleptic drugs was found: Haloperidol, spiroperidol and pimozide were profoundly antagonized by muscimol whereas cis(Z) - flupenthixol and fluphenazine were less antagonized. Baclofen shows no significant effect. Diazepam and scopolamine also strongly antagonized the antistereotypic effect of the butyrophenone-like compounds whereas only scopolamine could antagonize fluphenazine and cis(Z) - flupenthixol. Therefore we conclude that if the antistereotypic effect of neuroleptics correlates to the antipsychotic effect, a GABA agonist would probably not potentiate the antipsychotic effect of neuroleptics but rather antagonize it.