Push-pull perfusion of pentylenetetrazol in the brain stem of 'encéphale isolé' cats

Nine 'encéphale isolé' cats had 'push-pull' perfusions of pentylenetetrazol (PTZ) in various loci of the brain stem, while the EEG from the right and left motor cortices, EMG from neck muscles, ocular movements and clinical changes were recorded. Perfusions in the rostral MRF induced bilateral rhythmic paroxysmal EEG discharges and myoclonic twitching of neck and head, more prominent in the muscles contralateral to the perfused side. PTZ in the caudal MRF induced tonic-clonic paroxysmal EEG discharges and EMG seizures, similar to those seen when PTZ is injected systemically. Perfusion in the PRF induced EEG spindle bursts, muscular hypotonia and myosis. When perfusion in the MRF inducing rhythmic paroxysmal EEG discharges and myoclonic twitching was followed by perfusion in the PRF, the EEG discharges were not modified, but the myoclonic movements were abolished. Perfusions outside the MRF and PRF did not produce obvious changes other than tonic gaze deviation to the contralateral side or nystagmus. The results suggest that PTZ has a differential effect in various structures of the CNS, producing primary generalized convulsive seizures when acting directly on the MRF.