Acetylcholine secretion enhanced by glutamate in rat embryonic spinal motoneurons: Respective involvement of NMDA and AMPA receptors

The spontaneous acetylcholine secretion and endogenous acetylcholine conten t were measured by means of chemiluminescent assay from isolated embryonic rat spinal motoneurons. The sensitivity of the detection allows to study th e kinetics of the acetylcholine secretion with short time intervals, Follow ing the demonstration of the presence of acetylcholine and glutamate in emb ryonic motoneurons, the aim of this work was to study the characteristics o f acetylcholine secretion and the effect of glutamate in its modulation. Th e involvement of NMDA and AMPA glutamatergic receptors was mainly studied. Our data show that spontaneously acetylcholine secretion, is not calcium-de pendent and is significantly enhanced by glutamate (1 mM). Pharmacological approaches show that glutamate effect on acetylcholine secretion is decreas ed in presence of APV (50 mu M and 100 mu M), or in presence of GYKI 53655 (10 mu M), demonstrating that both NMDA and AMPA receptors are present at t he membrane of embryonic spinal motoneurons and involved in the modulation of acetylcholine secretion. Presence of glutamate in the embryonic motoneur on and secretion may represent a mechanism of control of extracellular acet ylcholine concentration, which was shown to control neuritic growth at earl y embryonic stage.