Opposite locomotor asymmetries elicited from the medial and lateral substantia nigra: role of the superior colliculus.

The present study investigated the role of the superior colliculus (SC) in the expression of opposing locomotor asymmetries elicited from the medial and lateral substantia nigra pars compacta (SNC). In experiment one it was found that amphetamine stimulated ipsiversive circling produced by unilateral SC lesions was additive with the ipsiversive circling produced by alpha-flupenthixol microinjections into the lateral SNC but was not additive with the contraversive circling produced by such injections into the medial SNC. Experiment two showed that the amphetamine stimulated ipsiversive circling produced by unilateral SC lesions was additive with the contraversive circling produced by lateral SNC lesions but was not additive with the ipsiversive circling produced by medial SNC lesions.

The role of the midbrain reticular formation in the expression of two opposing nigral denervation syndromes.

The present study investigated the role of the midbrain reticular formation (MRF) in the expression of opposing locomotor asymmetries elicited from the medial and lateral substantia nigra pars compacta (SNC). It was found that unilateral MRF lesions produced ipsiversive circling that was potentiated by amphetamine. Lateral SNC lesions produced contraversive circling while medial SNC lesions caused ipsiversive circling.