STIMULATION OF NTS ACTIVATES NMDA AND NON-NMDA RECEPTORS IN RAT CARDIAC VAGAL NEURONS IN THE NUCLEUS AMBIGUUS

While it is widely accepted that tonic and reflex changes in cardiac v agal activity play significant roles in cardiovascular function, littl e is known about the synaptic pathways in the brainstem responsible fo r the control of cardiac vagal neurons in the nucleus ambiguus (NA). I n this study, we identified the principal post-synaptic receptors acti vated in cardiac vagal neurons upon stimulation of the nucleus tractus solitarius (NTS). Cardiac vagal neurons were identified by the presen ce of a retrograde fluorescent tracer and were visualized in rat brain stem slices. Perforated patch clamp techniques were used to record pos t-synaptic currents. NTS stimulation activated glutamatergic currents in cardiac vagal neurons with a typical delay of 8-18 ms. Post-synapti c responses were separated into NMDA and non-NMDA components using D-2 -amino-5-phophonovalerate (AP5) and 6-cyano-7-nitroquinoxaline-2,3-dio ne (CNQX), respectively. In conclusion, this study characterizes a mon osynaptic glutamatergic pathway from NTS that activates NMDA and kaina te/AMPA post-synaptic receptors in cardiac vagal neurons. (C) 1998 Els evier Science B.V.