Contribution of NMDA and nonNMDA glutamate receptors to synchronized excitation and cortical output in the primary motor cortex of the rat.

Application of a GABA (gamma-aminobutyric acid) type A receptor antagonist through a microdialysis probe into the forelimb primary motor cortex (MI) of ketamine anesthetized rats induced the appearance of paroxysmal field potentials recorded in the supragranular layers of the MI and concomitant electromyographic (EMG) activity in the contralateral forelimb. Application of a nonNMDA (N-methyl-D-aspartate) glutamate receptor antagonist in conjunction with the GABA type A receptor antagonist completely blocked the paroxysmal field potentials and the EMG activity of the contralateral forelimb, while a NMDA receptor antagonist had no effect. The results indicate that the spread of activity within the primary motor cortex and the motor cortex output are mediated by nonNMDA receptors.