Facilitation of the Bezold-Jarisch reflex by central stimulation of alpha 2 adrenoceptors in dogs.

Abstract	The Bezold-Jarisch reflex characterized by hypotension and bradycardia was elicited in anaesthetized artificially respired dogs (pretreated with a beta-adrenoceptor antagonist ) using capsaicin 10 micrograms/kg (i.v.). Intracisternal administration of the highly selective "clonidine-like" alpha 2 adrenoceptor agonists B-HT 920 (10 micrograms/kg) or B-HT 933 (30 micrograms/kg) significantly facilitated this reflex bradycardia. The involvement of central alpha 2-adrenoceptors is suggested as intracisternal administration of the alpha 2 adrenoceptor blocking drugs yohimbine (50 micrograms/kg) and piperoxan (50 micrograms/kg) antagonized this facilitation. B-HT 920 also facilitated the vagally mediated baroreceptor reflex to the hypertensive effect of intravenous noradrenaline (3 micrograms/kg). Although the Bezold-Jarisch reflex and the baroreceptor reflex have different afferent pathways, both reflexes may either converge into a common pathway or have separate neuronal chains within the medulla; however, this study indicates that both have a similar central modulatory system stimulated by alpha 2 adrenoceptors.
Authors	D W Harron, W Kobinger
Journal	Naunyn-Schmiedeberg's archives of pharmacology (Naunyn Schmiedebergs Arch Pharmacol) Vol. 325 Issue 3 Pg. 193-7 (Mar 1984) ISSN: 0028-1298 [Print] Germany
PMID	6145098 (Publication Type: Journal Article)
Chemical References	Adrenergic alpha-Agonists Adrenergic alpha-Antagonists Azepines Receptors, Adrenergic, alpha Yohimbine talipexole Piperoxan azepexole Capsaicin
Topics	Adrenergic alpha-Agonists (pharmacology) Adrenergic alpha-Antagonists (pharmacology) Animals Azepines (pharmacology) Blood Pressure (drug effects) Capsaicin (pharmacology) Dogs Female Heart Rate (drug effects) Male Piperoxan (pharmacology) Pressoreceptors (physiology) Receptors, Adrenergic, alpha (drug effects) Reflex (physiology) Respiration, Artificial Vagus Nerve (physiology) Yohimbine (pharmacology)

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