Involvement of NMDA and NonNMDA 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-relatedneuronal activity of the primary motor cortex (MI), premotorcortex (PM), supplementary motor area (SMA), and an area rostralto the SMA (pre-SMA) of two monkeys (Macace fuscata) was examinedduring performance of a trained motor task. The selective NMDAantagonist 0-2-amino-5-phosphonovaleric acid (APV) and the non-NMDAantagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) wereiontophoretically applied to motor task-related neurons. A totalof 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 individualneurons. In many neurons, APV selectively or preferentiallysuppressed the spontaneous discharge rather than movement-relatedactivity. In many neurons, the movement-related activity wasmore selectively or effectively suppressed by CNQX than by APV.However, the set-related activity was affected by both APV endCNQX. The neurons in layers I and II were affected more stronglyby APV end CNQX than those in layers V and VI. No correlationwas found between the magnitude of task-related activity inthe control (no drug application) period and the effectivenessof APV or CNOX. These results indicate that both NMDA and non-NMDAglutamate receptors are involved in motor task-related neuronalactivity of both primary and secondary motor areas, althoughthe contribution of these two receptors to individual neuronalactivity varies a great deal.