Cardiovascular effects of serotonin in the nucleus of the solitary tract.
The cardiovascular regulatory role of serotonin [5-hydroxytryptamine (5-HT)] in the solitary tract nucleus (NTS) was investigated in urethan-anesthetized Wistar rats. Unilateral microinjection of 5-HT (5 nmol in 50 nl) into the NTS evoked depressions of both arterial pressure (-20 +/- 1 mmHg) and heart rate (-43 +/- 6 beats/min). Induction of bradycardia and hypotension was repeatable and consistently obtained with injections into the NTS but not into neighboring structures. Microinjection of the nonselective 5-HT receptor antagonist methiothepin or the 5-HT1A/5-HT1B antagonist pindolol prevented any cardiovascular change by subsequent microinjection of 5-HT into the NTS. In contrast, microinjection of the 5-HT2-selective antagonist ketanserin or the 5-HT1A antagonist spiroxatrine had no effect on the subsequent 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 the NTS evokes vagal chronotropic cardioinhibition and sympathetic withdrawal and suggest that this action is mediated by 5-HT1 serotonergic receptors, possibly of the 5-HT1B subtype.
Feldman
P D
PD
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Medical Center, New Orleans 70112-1393, USA.
Galiano
F J
FJ
D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology; D002319:Cardiovascular System / Q000187:drug effects*; D003714:Denervation; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D010276:Parasympatholytics / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014630:Vagus Nerve / Q000502:physiology
D001286:Atropine Derivatives; D010276:Parasympatholytics; D012702:Serotonin Antagonists; D012701:Serotonin; C006649:methylatropine