Hemodynamic effects of serotonin in the nucleus tractus solitarius.
Feldman, Peter D., and Floyd J. Galiano.
Department of Pharmacology and Experimental Therapeutics, Louisiana State
University Medical Center, 1901 Perdido Street, New Orleans, LA 70112-1393,
U.S.A.
APStracts 2:0010R, 1995.
The hemodynamic regulatory role of serotonin (5-HT) in the solitary tract
nucleus (nTS) was investigated in urethane-anesthetized Wistar rats.
Unilateral microinjection of 5-HT (5 nmol in 50 nL) into nTS evoked
depressions of both arterial pressure (-20 1 mm Hg) and heart rate (-43 6
bpm). Induction of bradycardia and hypotension was repeatable and
consistently obtained by injections into nTS, but not into neighboring
structures. Preceding microinjection of the broad-spectrum 5-HT receptor
antagonist methiothepin, or of the 5-HT1A/5-HT1B antagonist pindolol,
prevented any change of hemodynamics by subsequent microinjection of 5-HT
into nTS. In contrast, microinjection of the 5-HT2-selective antagonist
ketanserin, or of the 5-HT1A antagonist spiroxatrine, had no effect on the
subsequent hemodynamic effects of 5-HT. Bilateral vagal denervation prevented
the bradycardia induced by 5-HT, whereas the vasodepression remained intact.
These data provide evidence that 5-HT in nTS evokes an excitation of vagal
chronotropic cardioinhibition and sympathetic withdrawal, and suggests that
this action is mediated by 5-HT1 serotonergic receptors, possibly of the 5
-HT1B subtype.
Received 24 June 1994; accepted in final form 10 January 1995
APS Manuscript Number R349-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative Comp.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.