Capsaicin-evoked bradycardia in anesthetized guinea pigs is mediated by endogenous tachykinins

Regulatory Peptides
J C Hancock, D B Hoover

Abstract

The present study was done to characterize the effects of endogenous tachykinins on heart rate in urethane-anesthetized guinea pigs. Intravenous injection of capsaicin (32 nmol/kg) was used to evoke release of tachykinins and calcitonin gene-related peptide (CGRP) from cardiac sensory nerve fibers. Such injections caused a brief decrease in heart rate (-37+/-7 beats/min, n=6) that was followed by a more prolonged increase (+44+/-10 beats/min). Blood pressure was lowered by -11+/-2 mmHg. Bilateral vagotomy did not affect the chronotropic or depressor responses to capsaicin, but atropine (1 micromol/kg) nearly abolished the bradycardic response (-8+/-3 beats/min, n=7). Combined blockade of NK2 and NK3 receptors, with SR48968 and SR14801 respectively, also caused a significant reduction of capsaicin-evoked bradycardia (-14+/-3 beats/min, n=4) but did not affect bradycardia evoked by vagal nerve stimulation. Blockade of CGRP receptors eliminated capsaicin-evoked tachycardia and prolonged the capsaicin-evoked bradycardia. These findings suggest that capsaicin-evoked bradycardia in the anesthetized guinea pig is mediated by tachykinins that stimulate cardiac cholinergic neurons. This effect appears to be truncated by the positive chr...Continue Reading

References

Jan 1, 1990·Journal of Cardiovascular Pharmacology·D L Barringer, R D Buñag
Sep 1, 1988·Journal of the Autonomic Nervous System·D B Hoover, J C Hancock
Jan 1, 1988·General Pharmacology·C A Maggi, A Meli
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Jan 1, 1995·British Journal of Pharmacology·H Chiao, R W Caldwell
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Feb 24, 2001·Japanese Journal of Pharmacology·D B HooverL Zhang
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Nov 1, 2005·Journal of Pharmacological Sciences·Lili ZhangDonald B Hoover
Jun 26, 2007·American Journal of Physiology. Heart and Circulatory Physiology·Beihua Zhong, Donna H Wang

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Citations

Feb 9, 2010·Autonomic Neuroscience : Basic & Clinical·Yaw-Syan FuHung-Tu Huang
Sep 6, 2013·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Viktor V FeketaSean P Marrelli
Jun 28, 2016·American Journal of Physiology. Heart and Circulatory Physiology·Matthew R StoyekFrank M Smith

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