INVOLVEMENT OF NMDA AND NON-NMDA RECEPTORS IN MOTOR TASK-RELATED ACTIVITY IN THE PRIMARY AND SECONDARY CORTICAL MOTOR AREAS OF THE MONKEY

The involvement of the NMDA and non-NMDA receptors in the task-related neuronal activity of the primary motor cortex (MI), premotor cortex (PM), supplementary motor area (SMA), and an area rostral to the SMA (preSMA) of two monkeys (Macaca fuscata) was examined during performance of a trained motor task. The selective NMDA antagonist D-2-amino-5-phosphonovaleric acid (APV) and the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were iontophoretically applied to motor task-related neurons. A total of 568 task-related neurons (435 movement related, 83 set related, 50 mixed type) were recorded from the MI, PM, SMA, and pre-SMA, and the effects of APV and CNQX were examined in the individual neurons. In many neurons, APV selectively or preferentially suppressed the spontaneous discharge rather than movement-related activity. In many neurons, the movement-related activity was more selectively or effectively suppressed by CN(IX than by APV. However, the set-related activity was affected by both APV and CNQX. The neurons in layers I and II were affected more strongly by APV and CNQX than those in layers V and VI. No correlation was found between the magnitude of task-related activity in the control (no drug application) period and the effectiveness of APV or CNQX. These results indicate that both NMDA and non-NMDA glutamate receptors are involved in motor task-related neuronal activity of both primary and secondary motor areas, although the contribution of these two receptors to individual neuronal activity varies a great deal.