AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 2 487-R491, Copyright © 1995 by American Physiological Society
Effects of L-arginine-derived nitric oxide synthesis on neuronal activity in nucleus tractus solitarius
S. Ma, F. M. Abboud and R. B. Felder
Cardiovascular Center, University of Iowa College of Medicine, Iowa City 52242.
The purpose of these studies was to determine the effects of
L-arginine-derived nitric oxide (NO) synthesis on neuronal activity in
solitary tract nucleus (NTS) neurons. Single unit activity was recorded
extracellularly from medial NTS neurons in Fischer-344 rats in vivo and in
vitro. In anesthetized rats with arterial pressure maintained constant,
NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv), an inhibitor of NO
synthesis, decreased the discharge rate in 12 of 14 neurons and increased
the discharge rate in two. After injection of L-NAME, the slowing of
neuronal activity began within 2-5 min, and maximal responses were observed
12-15 min after injection. The decreases in activity were reversed within
12-15 min with L-arginine (30 mg/kg iv) or immediately with nitroglycerin
(NTG, 10-30 micrograms/kg iv). In superfused rat brain slices, the
discharge rate was reduced by 1 mM L-NAME in seven neurons, increased in
two, and unchanged in one. The decreases in discharge rate were reversed by
2 mM L-arginine (4 of 6 neurons) and by 10-30 microM NTG (6 of 7 neurons).
The results show that L-arginine-derived NO can affect the spontaneous
discharge rate of NTS neurons. We conclude that NO may influence the
excitability of NTS neurons involved in central autonomic control.
