3 TYPES OF POSTSYNAPTIC GLUTAMATERGIC RECEPTORS ARE ACTIVATED IN DMNXNEURONS UPON STIMULATION OF NTS

While it is widely accepted that parasympathetic activity plays a sign ificant role in cardiovascular, bronchomotor, and gastrointestinal fun ction, little is known about the synaptic control of parasympathetic v agal neurons. In this study, we identified the neurotransmitter(s) and postsynaptic responses in dorsal motor nucleus of the vagus (DMNX) ne urons upon stimulation of the nucleus of the solitary tract (NTS). Neu rons were visualized in rat brain stem slices, and perforated patch-cl amp techniques were used to record postsynaptic currents. NTS stimulat ion activated glutamatergic currents. NTS stimulation activated glutam atergic currents in DMNX that were separated into N-methyl-D-aspartate (NMDA) and non-NMDA components using D-2-amino-5-phosphonovalerate an d 6-cyano-7-nitroquinoxaline-2,3-dione, respectively. The non-NMDA com ponent was further characterized using cyclothiazide and concanavalin A to block desensitization of DL-alpha-3-hydroxy-5-methylisoxazole-pro pionic acid (AMPA) and kainate receptors, respectively. Cyclothiazide increased the postsynaptic amplitude, whereas concanavalin A augmented duration, suggesting kainate, but not AMPA, currents are curtailed by desensitization. High frequency stimulations did not alter synaptic e fficacy. In conclusion, this study demonstrates the existence of a mon osynaptic glutamatergic pathway from NTS that activates NMDA, kainate, and AMPA postsynaptic receptors in DMNX neurons.