The importance of the striato-nigro-collicular pathway in the expression of haloperidol-induced tonic electromyographic activity.

Experiments were carried out to investigate the participation of the striatonigral and nigrocollicular GABAergic pathways in the expression of haloperidol-induced tonic electromyographic (EMG) activity of the gastrocnemius-soleus muscle in awake rats. It was shown that bilateral injections of haloperidol (500 ng/0.5 microliter) into the rostral part of the neostriatum induced a tonic EMG activity which could be significantly reduced by a second bilateral injection of muscimol (25 ng/0.5 microliter) into the substantia nigra pars reticulata (SNR) or of bicuculline (50 ng/0.5 microliter) into the intermediate or deep layers of the colliculus superior (CS). These results suggest that the striatonigral and nigrocollicular GABAergic pathways play a critical role in the transmission of haloperidol-induced tonic EMG activity.