Modification of electroshock and pentylenetetrazol seizure patterns in rats after precollicular transections.

Rats with precollicular transections leaving the brain stem intact were subjected to electroshock or pentylenetetrazol-induced convulsions. Animals with transections failed to display the face and forelimb clonus (with or without rearing) typically seen in sham-operated rats subjected to pentylenetetrazol- or minimal electroshock-induced convulsions elicited with corneal electrodes. Moreover, rats with transections exhibited all other components of pentylenetetrazol- and electroshock-induced seizures. These findings support the hypothesis that tonic and some types of clonic convulsions can occur independently of seizure discharge in forebrain structures, whereas clonus restricted to the face and forelimbs depends on seizure discharge emanating from structures within the forebrain for expression.