Transcallosally evoked potentials and the EEG in the decerebrate dog: Actions of tryptaminergic, dopaminergic and adrenergic agonists

The midpontine decerebrate dog, immobilized with gallamine, was used to determine the changes in the transcallosally evoked potential (TEP) produced by intravenous infusions of various drugs. A total of 50 TEPs, recorded from the g. ectolateralis, was computer analyzed before, during and after administration of the drugs. Changes in the TEP were also correlated with changes in the EEG recorded from the g. ectolateralis. The EEG was analyzed by inspection and amplitude integration (electrogenesis). LSD (30 μg/kg) significantly depressed the TEP, and the effect persisted for at least 80 min. DMT (1 mg/kg) caused a significant and reversible increase in the amplitude of the TEP. LSD and DMT reduced the alpha activity of the EEG and enhanced the amplitude of the low-frequency waves. DMT produced a significant and LSD a marginal increase in electrogenesis. Tryptamine (10 and 20 mg/kg), mescaline (6 mg/kg), methoxamine (0.88 mg/kg) and apomorphine (5 mg/kg) had no significant effect on the TEP or EEG. These results suggest that depression of the TEP is not related to spinal reflex facilitation in the dog or hallucinogenic activity in man.