Three types of post-synaptic glutamatergic receptors are activated
in dmnx neurons upon stimulation of nts.
Willis, A., M. Mihalevich, R. A. Neff, and D. Mendelowitz.
Department of Physiology and Biophysics, University of Tennessee,
894 Union Ave., Memphis, TN 38163
APStracts 3:0262R, 1996.
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 post-synaptic responses in dorsal motor
nucleus of the vagus (DMNX) neurons upon stimulation of the nucleus
tractus solitarius (NTS). Neurons were visualized in rat brainstem
slices and perforated patch clamp techniques were used to record
post-synaptic currents. NTS stimulation activated glutamatergic
currents in DMNX that were separated into NMDA and non-NMDA
components using D-2-amino-5-phophonovalerate (AP5) and 6-cyano-7
-nitroquinoxaline-2,3-dione (CNQX), respectively. The non-NMDA
component was further characterized using cyclothiazide and
concanavalin A to block desensitization of 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
post-synaptic receptors in DMNX neurons.
Received 26 December 1995; accepted in final form 14 June 1996.
APS Manuscript Number R817-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96