Intranigral injection of muscimol induced hyperactivity in rats and antagonized haloperidol-induced catalepsy. Intranigral injection of gabaculine, an inhibitor of GABA transaminase, induced similar effects 5h after injection, when the nigral GABA content was increased 7-fold. On the other hand, injections of muscimol (30 ng) into the globus pallidus potentiated the cataleptic effect of haloperidol, and muscimol alone in high doses (100 and 200 ng) induced catalepsy. Gabaculine also induced catalepsy of medium intensity and potentiated the effect of haloperidol 24h after injection, when GABA was increased in the globus pallidus as well as in the substantia nigra. Injections of muscimol into either the globus pallidus or substantia nigra increased striatal HVA and enhanced haloperidol-induced elevation of HVA. Three benzodiazepines, nitrazepam, diazepam and chlordiazepoxide administered orally, potentiated the effect of muscimol (30 ng) injected into the globus pallidus and induced catalepsy. A similar effect was not obtained with phenobarbital. It is suggested that stimulation of GABA receptor or increase of GABA content in the sustantia nigra antagonize haloperidol-induced catalepsy by activation of nigral dopaminergic system, and that enhancement of pallidal GABA function induces catalepsy by non-dopaminergic mechanisms. Potentiation of haloperidol-induced catalepsy by benzodiazepines may be due to enhancement of GABA-ergic transmission within the globus pallidus.

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A series of methyl 9H-pyridazino[3,4-b]indole-3-carboxylates and related compounds were synthesized using a Diels-Alder reaction of methyl 3-(1H-indol-3-yl)-2-propenoates and dibenzyl azodicarboxylate. Several compounds were found to have high affinity for the benzodiazepine receptor. Their structure-activity relationships are discussed.

This experiment was conducted to examine effects of oxazolam, cloxazolam, CS-386, and reference drugs on socially induced suppression and aggression in pairs of monkeys. Oxazolam, cloxazolam, and CS-386, as well as other benzodiazepines, at both ataxic and non-ataxic doses, attenuated the socially induced suppression, but failed to show inhibitory effect on the on the socially induced aggression. Chlorpromazine, at both slight-sedative and non-sedative doses, reduced neither socially induced suppression nor aggression. Imipramine did not produce any significant effect in this study.

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