Endomorphins decrease heart rate and blood pressure possibly by activating vagal afferents in anesthetized rats.

E H Kwok; N J Dun

doi:10.1016/s0006-8993(98)00623-4

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Endomorphins decrease heart rate and blood pressure possibly by activating vagal afferents in anesthetized rats.

E H Kwok·N J Dun

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Abstract

Endomorphin 1 (10, 30, 100 nmol/kg) administered intravenously (i.v. ) to urethane-anesthetized rats consistently and dose-dependently lowered heart rate (HR) and mean arterial pressure (MAP); the decrease in blood pressure recovered faster as compared to the HR. The effects of endomorphin 2 were qualitatively similar. Naloxone (2 mg/kg, i.v.) completely antagonized the bradycardia and hypotension caused by endomorphin 1. Pretreatment of the rats with atropine methylnitrate, atropine sulfate (2 mg/kg, i.v.) or bilateral vagotomy nearly abolished the bradycardia and attenuated the hypotensive effect of endomorphin 1. Our studies suggest that the bradycardia effect following systemic administration of the new opioid peptide may be explained by activation of vagal afferents and the hypotensive effect may be secondary to a reduction of cardiac output and/or a direct vasodilation.

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Analgesics, Opioid Animals Blood Pressure Heart Rate Injections, Intraperitoneal Injections, Intravenous Male Oligopeptides Rats Rats, Sprague-Dawley Receptors, Opioid, mu Vagus Nerve Journal Article Research Support, U.S. Gov't, P.H.S.

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E H Kwok, N J Dun. 1998-08-24. Endomorphins decrease heart rate and blood pressure possibly by activating vagal afferents in anesthetized rats.. https://doi.org/10.1016/s0006-8993(98)00623-4

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