Muscle NMDA receptors regulate the resting membrane potential through NO-synthase.

The early postdenervation depolarization of rat diaphragm muscle fibres (8-10 mV) is substantially smaller (3 mV) when muscle strips are bathed with 1 mM L-glutamate (GLU) or N-methyl-D-aspartate (NMDA). The effects of GLU and NMDA are not seen in the presence of aminophosphonovaleric acid (APV), a blocker of NMDA-subtype of glutamate receptors, 5 mM Mg2+ (which blocks NMDA-controlled ion channels) and L-nitroarginine methylester (NAME), an inhibitor of NO-synthase. This indicates that NMDA-subtype of GLU receptors might be involved in the regulation of the membrane potential in muscle fibres, most probably through the NO-synthase system.