Abstract |
Hemorrhage in rats produces reflex decreases in heart rate (HR) and renal sympathetic nerve activity (RSNA). Because serotonergic antagonists attenuate hemorrhage-induced vagal-mediated bradycardia, we determined whether blockade of serotonin synthesis by p-chlorophenylalanine (PCPA) or of serotonin receptors with methysergide would also abolish the renal sympathoinhibition. Mean arterial pressure (MAP), HR, and RSNA were recorded in chloralose-anesthetized rats pretreated with PCPA (300 mg.kg-1.day-1 X 3 days ip, n = 12) or vehicle (0.3 ml saline, n = 9). During hemorrhage, where MAP was maintained at 50 mmHg for 8 min, vehicle-treated rats decreased HR by 27 +/- 13 beats/min and RSNA by -55 +/- 7%. In PCPA-treated rats, HR and RSNA did not change. Cervical vagotomy abolished the bradycardia and sympathoinhibition during hemorrhage. After acute administration of methysergide (400 micrograms/kg iv, n = 8) hemorrhage produced increases of RSNA, whereas vehicle (0.5 ml saline, n = 7) preserved the renal sympathoinhibition to hemorrhage in conscious rats. Finally, volume expansion (0.88 ml blood/100 g body wt) produced comparable decreases in RSNA in sinoaortic-denervated rats pretreated with PCPA (n = 11) or vehicle (n = 10) (-58 +/- 9 vs. 47 +/- 7%, respectively). We conclude that serotonergic mechanisms are critically involved in vagal afferent inhibition of RSNA during severe hemorrhage in rats.
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Authors | D A Morgan, P Thoren, E A Wilczynski, R G Victor, A L Mark |
Journal | The American journal of physiology
(Am J Physiol)
Vol. 255
Issue 3 Pt 2
Pg. H496-502
(Sep 1988)
ISSN: 0002-9513 [Print] United States |
PMID | 2843055
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- Phenylephrine
- Serotonin
- Fenclonine
- Methysergide
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Topics |
- Animals
- Blood Pressure
(drug effects)
- Denervation
- Female
- Fenclonine
(pharmacology)
- Heart Rate
(drug effects)
- Hemorrhage
(physiopathology)
- Kidney
(innervation)
- Methysergide
(pharmacology)
- Phenylephrine
(pharmacology)
- Pressoreceptors
(drug effects, physiology)
- Rats
- Rats, Inbred Strains
- Reference Values
- Serotonin
(physiology)
- Sinus of Valsalva
(innervation)
- Sympathetic Nervous System
(physiology, physiopathology)
- Synaptic Transmission
- Vagotomy
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