Tachycardia evoked by disinhibition of the dorsomedial hypothalamus in rats is mediated through medullary raphe

B. C. Samuels, Dmitry Zaretsky, J. A. DiMicco

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Abstract

Activation of neurons in the region of the dorsomedial hypothalamus (DMH) appears to generate the sympathetically mediated tachycardia seen in experimental stress in rats. The purpose of this study was to assess the role of neurons in the area of the medullary raphe pallidus (RP) in the tachycardia caused by stimulation of the DMH. The cardiovascular response to microinjection of the GABAA receptor antagonist bicuculline methiodide (BMI) 10 pmol (100 nl)-1 into the DMH was assessed before, and after, injection of the GABAA receptor agonist muscimol 80 pmol (100 nl)-1 or saline vehicle 100 nl into the RP in urethane-anaesthetized rats. Tachycardia evoked by microinjection of BMI into the DMH was mimicked by microinjection of BMI 30 pmol (75 nl)-1 into the RP. This DMH-induced tachycardia was markedly suppressed after injection of muscimol into the RP, but the response was unaffected by injection of saline into the same region. Thus, DMH-induced tachycardia is mediated through activation of neurons in the area of the RP, suggesting that these neurons may play a previously unrecognized role in stress-induced cardiac stimulation.

Original languageEnglish
Pages (from-to)941-946
Number of pages6
JournalJournal of Physiology
Volume538
Issue number3
DOIs
StatePublished - Feb 1 2002

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Tachycardia
Hypothalamus
Microinjections
Neurons
Muscimol
Injections
GABA-A Receptor Agonists
GABA-A Receptor Antagonists
Urethane
bicuculline methiodide

ASJC Scopus subject areas

  • Physiology

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Tachycardia evoked by disinhibition of the dorsomedial hypothalamus in rats is mediated through medullary raphe. / Samuels, B. C.; Zaretsky, Dmitry; DiMicco, J. A.

In: Journal of Physiology, Vol. 538, No. 3, 01.02.2002, p. 941-946.

Research output: Contribution to journalArticle

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