AN NMDA RECEPTOR ON ISOLATED SECRETORY NERVE-ENDINGS

While the presence of post-synaptic NMDA receptors in the CNS is well- established, the present study addressed the question of whether NMDA receptors may also be present on secretory nerve endings. Using micros pectrofluorometry of fura-2 loaded isolated neurohypophysial nerve end ings of the rat, we found that both glutamate (EC(50) = 50 mu M) and N MDA (EC(50) = 30 mu M) induced a rapid rise in (Ca2+](i). These respon ses were glycine-dependent and abolished by 1 mM Mg2+, 1 mu M dizocilp ine, and removal of extracellular Ca2+. Responses were not significant ly affected by treatment with Ca2+ channel blockers or 10 mu M CNQX.