Dopaminergic modulation of transcallosal activity of cat motor cortical neurons

The effects of dopamine (DA) and its antagonists on the transcallosal activ ity of pyramidal tract neurons (PTNs) and non-PTNs in the anesthetized cat motor cortex were studied with iontophoretic applications; dopamine, SCH 23 390 (D1 antagonist), sulpiride (D2 antagonist) and haloperidol. Neuronal ac tivity was recorded with a multi-barreled glass microelectrode. Transcallos al neuronal activity was evoked by stimulation of the contralateral motor c ortex. The number of spikes thus activated was counted for the control and test conditions after application of each drug: (1) dopamine application de creased the number of spikes evoked by transcallosal stimulation; (2) appli cation of SCH 23390, sulpiride and haloperidol restored these decreased spi ke numbers to the control level; (3) latency of neuronal response to transc allosal stimulation was not affected by the application of either DA, SCH 2 3390, sulpiride or haloperidol; and (4) there was no significant difference between PTNs and non-PTNs in the manner of response to DA and its antagoni st applications. Our conclusion is that dopamine modulated the transcallosa l neuronal response in the cat motor cortex in a suppressive manner. This f act suggested that interhemispheric neuronal communications could be subjec ted to suppressive modification by the dopaminergic system. (C) 1999 Elsevi er Science Ireland Ltd. All rights reserved.