Antagonism of experimentally induced tonic seizures following a lesion in the midbrain tegmentum.

Midbrain tegmental lesions, which prevent the hindlimb extensor (HLE) component of maximal electroshock seizures (MES), were found to have no effect on the electroshock, flurothyl, or pentylenetetrazol (PTZ) seizures thresholds. However, these lesions were found to antagonize the HLE component of the maximal PTZ seizure, and to elevate the threshold for electroshock induced tonic flexion. These findings suggest that lesion of the midbrain tegmentum involving the superior cerebellar peduncle and/or the midbrain reticular formation antagonize the tonic component of generalized seizures, but have little or no effect on the clonic component.