Possible nicotinic receptor-mediated modulation of synaptic
transmission in nucleus tractus solitarius.
Shiraki, Takuma, Atsushi Toyoda, Haruhiko Sugino, Aiko Hori, and
Shigeo Kobayashi.
Department of Neuroscience, Graduate School of Human and
Environmental Studies, Kyoto University, Kyoto 606, Japan
APStracts 3:0360R, 1996.
Signal transmission from afferent nerves to neurons in the nucleus
tractus solitarius (NTS) may be mediated partially by nicotinic
acetylcholine receptors (nAChRs). Here, we investigated nAChR
-mediated signal transmission using rat NTS slices. Firstly, we
characterized nAChRs by obtaining patch-clamp recordings from NTS
neuronal cell bodies. Under whole-cell voltage-clamp conditions at
-60 mV, application of nicotine induced an inward current, and this
effect was blocked by hexamethonium. In outside-out patch recordings,
nicotine was seen to induce a hexamethonium-sensitive single channel
current. Secondly, we investigated nAChR-mediated signal
transmission. Fast synaptic transmission mediated by nAChRs was not
detected. The action of diffusible acetylcholine (ACh) on nAChRs was
then tested using the outside-out patches excised from NTS neurons as
probes for ACh. When the patch was placed at a distance of 20-30
[mu]m from the cell body, single channel currents were recorded, and
these were inhibited by hexamethonium. The frequency of channel
opening was increased by high [K+]o solution, suggesting the voltage
-dependent release of ACh which acts on nAChRs. These results
suggested that nAChR-mediated signal transmission from sensory
afferents to NTS neurons is in part mediated by diffusible ACh.
Received 27 November 1995; accepted in final form 3 September
1996.
APS Manuscript Number R747-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996