5-hydroxytryptamine inhibits pressor responses to preganglionic sympathetic nerve stimulation in pithed rats.
5-Hydroxytryptamine (5-HT) inhibits contractile responses to adrenergic nerve stimulation in several blood vessels and organs. We have now investigated the potential ability of 5-HT to inhibit the pressor responses caused by preganglionic sympathetic stimulation (T7-T9) in pithed rats. Sympathetic stimulation (0.03, 0.1, 0.3, 1 and 3 Hz) resulted in frequency-dependent increases in diastolic blood pressure; these effects were augmented after i.v. treatment with desipramine (50 micrograms/kg). During continuous infusions of 5-HT (1.8, 3.1, 5.6 and 10 micrograms/kg.min, i.v.), but not of saline, the pressor responses were dose-dependently inhibited in both control and desipramine-pretreated rats; this inhibitory effect of 5-HT was significantly more pronounced at lower frequencies of stimulation. In contrast, the above infusions of 5-HT did not inhibit the pressor responses induced by i.v. bolus injections of exogenous norepinephrine (up to 3 micrograms/kg). Taken together, the above findings suggest an operative 5-HT-induced prejunctional inhibition of sympathetic nerve activity on the systemic vasculature in vivo.
Villalón
C M
CM
Terapéutica Experimental, CINVESTAV, I.P.N., México D.F., México.
Contreras
J
J
Ramŕiez-San Juan
E
E
Castillo
C
C
Perusquía
M
M
López-Muñoz
F J
FJ
Terrón
J A
JA
D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000187:drug effects / Q000502:physiology; D003655:Decerebrate State; D003891:Desipramine / Q000494:pharmacology; D004558:Electric Stimulation; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D009433:Neural Inhibition; D011311:Pressoreceptors / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology
D012701:Serotonin; D012965:Sodium Chloride; D003891:Desipramine