Hypothyroid-induced changes in autonomic control have a central
serotonergic component.
Henley, William N., and Franjo Vladic.
Dept. of Biol. Sci. and Coll. of Osteo. Med., Ohio U., Athens, OH
45701
APStracts 3:0349H, 1996.
Three experiments were conducted in unanesthetized rats made
hypothyroid (Hypo) or maintained as euthyroid controls (Eu) to
examine: general cardiovascular responsiveness (Experiment I);
responsiveness to a 5HT2 agonist (DOI, i.c.v. ; Experiment II); or
responsiveness to a 5HT1A agonist (8-OH-DPAT, i.c.v.; Experiment
III). In Experiment I, i.v. infusions of phenylephrine and
nitroprusside provided little evidence that findings in Experiments
II & III were due to generalized impairment in cardiovascular
responsiveness in Hypo. In Experiments II & III, Eu and Hypo were
given either i.v. atropine or vehicle. Atropine significantly
elevated HR (Exp II & III) and arterial pressure (MAP; Exp II) in
Eu only. When comparedo Eu, Hypo had a reduced pressor response (5.2
vs 20.1%), an attenuated pulse pressure response (19.3 vs 35.4%) and
a more robust bradycardia (-17.7 vs -7.0%) in response to DOI. These
differences were atropine sensitive. In Exp III, Hypo had larger
decrements in MAP (-9.0 vs -5.1%), HR (-13.9 vs -7.7%), and body
temperature (TB ; -4.5 vs -2.7%) in response to 8-OH-DPAT in
comparison to Eu. Parasympathetic involvement in the differential
responses to 8-OH-DPAT was less clear than with DOI. Deranged
autonomic control in hypothyroidism may be due, in part, to changes
in central serotonergic activity.
Received 13 August 1996; accepted in final form 8 December 1995.
APS Manuscript Number H1143-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996