Blockade of 5-HT2A receptors suppresses hyperthermic but not cardiovascular responses to psychosocial stress in rats.
The aim of this study was to determine whether 5-HT2A receptors mediate cardiovascular and thermogenic responses to acute psychological stresses. For this purpose, adult male Wistar hooded rats instrumented for telemetric recordings of either electrocardiogram (ECG) (n=12) or arterial pressure (n=12) were subjected, on different days, to four 15-min episodes of social defeat. Prior to stress, animals received s.c. injection of the selective 5-HT2A receptor antagonist SR-46349B (trans-4-((3Z)3-[(2-dimethylaminoethyl)oxyimino]-3-(2-fluorophenyl)propen-1-yl)-phenol, hemifumarate) (at doses of 0.3, 1.0 and 3.0 mg/kg) or vehicle. The drug had no effect on basal heart rate or heart rate variability indexes, arterial pressure, and core body temperature. Social defeat elicited significant and substantial tachycardic (347+/-7 to 500+/-7 bpm), pressor (77+/-4 to 97+/-4 mm Hg) and hyperthermic (37.0+/-0.3 to 38.5+/-0.1 degrees C) responses. Blockade of 5-HT2A receptors, at all doses of the antagonist, completely prevented stress-induced hyperthermia. In contrast, stress-induced cardiovascular responses were not affected by the blockade (except small reduction of tachycardia by the highest dose of the drug). We conclude that in rats, 5-HT2A receptors mediate stress-induced hyperthermic responses, but are not involved in the genesis of stress-induced rises in heart rate or arterial pressure, and do not participate in cardiovascular control at rest.
Beig
M I
MI
School of Biomedical Sciences, University of Newcastle, Callaghan, NSW 2038, Australia.
Baumert
M
M
Walker
F R
FR
Day
T A
TA
Nalivaiko
E
E
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001831:Body Temperature / Q000187:drug effects*; D002319:Cardiovascular System / Q000187:drug effects / Q000503:physiopathology; D004562:Electrocardiography; D005334:Fever / Q000188:drug therapy / Q000503:physiopathology; D005464:Fluorobenzenes / Q000008:administration & dosage / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D010636:Phenols / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D012930:Social Dominance; D013315:Stress, Psychological / Q000188:drug therapy* / Q000503:physiopathology; D013610:Tachycardia / Q000188:drug therapy / Q000503:physiopathology
D005464:Fluorobenzenes; D010636:Phenols; D044402:Receptor, Serotonin, 5-HT2A; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists; C076033:SR 46349B