Role of dorsal mesencephalic reticular formation and deep layers of superior colliculus in turning behaviour elicited from the striatum.

Kainate or electrolytic lesions were placed unilaterally in the dorsal mesencephalic reticular formation (MRF) or in the deep layers of the superior colliculus (DLSC) on the same side of a unilateral lesion of the medial forebrain bundle with 6-OHDA. Before the lesions the rats turned contralaterally when challenged with 0.25 mg/kg of apomorphine. After lesions of the MRF most rats turned ipsilaterally in response to the same dose of apomorphine. After lesions of the DLSC apomorphine-induced contralateral turning was significantly reduced but not abolished. The results indicate that the MRF and DLSC play a primary role in the expression of turning originated from the striatum.