Zona incerta-lateral hypothalamus as an output structure for impulses involved in neuroleptic drug-induced catalepsy.

Our previous studies showed that the neuronal impulses connected with catalepsy, which have their origin at dopamine D2 receptors in the ventro-rostral part of the nucleus caudatus-putamen in rats, are conveyed to the zona incerta-lateral hypothalamic region. The aim of the present study was to investigate the route of the neuronal impulses between these structures. The experiments were carried out on rats with cannulae chronically implanted in the brain structures. We showed that (1) bilateral injection of bicuculline methiodide (5-50 ng) into the ventro-medial part of the globus pallidus (GPv) and (2) bilateral injection of muscimol (2.5-25 ng) into the substantia nigra pars reticulata (SNR) inhibit, in a dose dependent manner, the catalepsy induced by sulpiride (1 microgram) administered bilaterally into the ventro-rostral part of the nucleus caudatus-putamen. It was also demonstrated that muscimol (25 ng), injected bilaterally into the ventro-medial part of the globus pallidus, induces catalepsy which, in turn, is dose-dependently inhibited by either (1) muscimol (5-25 ng) injected into the substantia nigra pars reticulata, or (2) bicuculline (1.0-2.5 ng) injected into the zona incerta-lateral hypothalamus (ZI-LH). Moreover, even a dose as high as 50 ng of bicuculline, injected into the ventro-medial part of the globus pallidus, had no significant effect on the locomotor activity of rats.(ABSTRACT TRUNCATED AT 250 WORDS)