Intratectal glutamate suppresses pentylenetetrazole-induced spike-and-wave discharges

Cortical spike-and-wave discharges evoked in rats by low (20-50 mg/kg) doses of subcutaneous pentylenetetrazole were suppressed by bilateral microinjection of sodium L-glutamate (100 mM, 200 nl/side) into the superior colliculus. Injections of saline into the superior colliculus, or glutamate into overlying cortex, were ineffective. This result is predicted by the hypothesis that the antiepileptic effects of nigral inactivation are at least partly mediated by the inhibitory nigrotectal pathway that runs from substantia nigra pars reticulata to the superior colliculus.