An investigation of the role played by the superior colliculus and ventromedial thalamus in self-injurious behavior produced by intranigral microinjection of muscimol.

Bilateral injection of muscimol (30 or 60 ng) into the substantia nigra (pars reticulata) of rats produced a variety of stereotyped acts, self-injurious behavior (SIB), and antinociception. Bilateral electrolytic lesions of the superior colliculus strongly suppressed SIB without reducing the antinociceptive effects of intranigral muscimol. Electrolytic lesions of the ventromedial thalamus had no effect on behavioral responses to intranigral muscimol. These studies suggest that the SIB produced by intranigral muscimol is mediated by neuronal pathways that terminate in or pass through the superior colliculus. The ventromedial thalamus does not appear to play a role in mediating behavioral responses to intranigral muscimol.