The role of gamma-aminobutyric acid mechanisms of the zona incerta-lateral hypothalamus in the catalepsy and muscle rigidity evoked by morphine.

Picrotoxin or bicuculline were injected bilaterally into the zona incerta-lateral hypothalamus (ZI-LH) of the rat. Each drug (50 ng) inhibited or abolished the catalepsy induced by 20 mg/kg s.c. of morphine. Each drug also strongly inhibited the tonic electromyographic activity (EMG) induced by 10 mg/kg s.c. of morphine in the gastrocnemius soleus muscle (GS). The obtained results demonstrate participation of the ZI-LH in both catalepsy and rigidity induced by a systemic administration of morphine.