[Commissural and sensory evoked potentials of the hippocampus upon microiontophoresis of several substances].

The effects of sodium glutamate, GABA, atropine, and acetylcholine microiontophoresis on the focal responses evoked by the stimulation of the forepaw and the contralateral hippocampus, were studied in unanesthetized immobilized rats. No significant changes were observed in sensory potentials following the application of these drugs. The microiontophoresis of glutamate to the recording site produced changes of the commissural responses. The positive wave was markedly depresses on 200-450 microns depth. At the same time the negative wave increased gradually in amplitude. In records from the layer of the apical dendritic shafts the negative commissural response component increased following local injection of glutamate. GABA failed to evoke changes in the commissural response though prevented the effect of glutamate. The possible differences in the mechanisms of commissural and sensory evoked potentials responsible for the effects observed are discussed.