MUSCLE NMDA RECEPTORS REGULATE THE RESTING MEMBRANE-POTENTIAL THROUGHNO-SYNTHASE

The early postdenervation depolarization of rat diaphragm muscle fibre s (8-10 mV) is substantially smaller (3 mV) when muscle strips are bat hed with 1 mM L-glutamate (GLU) or N-methyl-D-aspartate (NMDA). The ef fects of GLU and NMDA are not seen in the presence of aminophosphonova leric acid (APV), a blocker of NMDA-subtype of glutamate receptors, 5 mM Mg2+ (which blocks NMDA-controlled ion channels) and L-nitroarginin e 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.