Three types of postsynaptic glutamatergic receptors are activated in DMNX neurons upon stimulation of NTS.

While it is widely accepted that parasympathetic activity plays a significant role in cardiovascular, bronchomotor, and gastrointestinal function, little is known about the synaptic control of parasympathetic vagal neurons. In this study, we identified the neurotransmitter(s) and postsynaptic responses in dorsal motor nucleus of the vagus (DMNX) neurons upon stimulation of the nucleus of the solitary tract (NTS). Neurons were visualized in rat brain stem slices, and perforated patch-clamp techniques were used to record postsynaptic currents. NTS stimulation activated glutamatergic currents in DMNX that were separated into N-methyl-D-aspartate (NMDA) and non-NMDA components using D-2-amino-5-phosphonovalerate and 6-cyano-7-nitroquinoxaline-2,3-dione, respectively. The non-NMDA component was further characterized using cyclothiazide and concanavalin A to block desensitization of DL-alpha-amino-3-hydroxy-5-methylisoxazole-propionic 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 efficacy. In conclusion, this study demonstrates the existence of a monosynaptic glutamatergic pathway from NTS that activates NMDA, kainate, and AMPA postsynaptic receptors in DMNX neurons.