Electrophysiological effects of capsaicin on guinea pig papillary muscles.
The cardiac electrophysiological effects of capsaicin (CAP) were examined in guinea pig papillary muscles using intracellular microelectrode technique. The results obtained are as follows: (1) the duration of action potential (APD) in normal papillary muscles was decreased by CAP (30, 60, 120 micromol/L) in a concentration-dependent manner; (2) in partially depolarized papillary muscles, 60 micromol/L CAP not only reduced APD, but also decreased the amplitude of action potential, overshoot and maximal velocity of phase 0 depolarization; (3) pretreatment with L-type Ca(2+) channel agonist Bay K8644 (0.5 micromol/L) could completely block the effects of CAP (60 micromol/L); (4) pretreatment with ruthenium red (20 micromol/L), a vanilloid receptor (VR) blocker, did not affect the actions of capsaicin on papillary muscles. All these results suggest that the effects of CAP on papillary muscles are likely due to a decrease in calcium influx which is not mediated by VR.
Li
Qian
Q
Department of Physiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang 050017.
Cheng
Yan-Ping
YP
He
Rui-Rong
RR
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001693:Biological Transport, Active; D002120:Calcium Channel Agonists / Q000494:pharmacology; D020746:Calcium Channels, L-Type; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008839:Microelectrodes; D010210:Papillary Muscles / Q000502:physiology*; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D012430:Ruthenium Red / Q000494:pharmacology
D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D011955:Receptors, Drug; D012430:Ruthenium Red; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002211:Capsaicin