[Role of catecholamines in action of nicotine on slow action potentials in guinea pig papillary muscles].
The action potential duration (APD) of histamine-induced slow action potentials (SAP) and force of contraction (FC) were potentiated by nicotine (0.6-1.0 mmol.L-1) on guinea pig papillary muscles in a concentration-dependent manner. In the presence of atropine, nicotine concentration dependently suppressed the action potential amplitude (APA), APD, the maximal upstroke velocity (Vmax), and FC in catecholamine-depleted (reserpine 2.5 mg.kg-1 ip, 15 h prior to the experiment) muscles. Nicotine (0.6 mmol.L-1) itself induced SAP and enhanced FC. These 2 effects were antagonized by verapamil. A linear relationship existed between APA of nicotine-induced SAP and 1g [Ca2+]0 with a slope of 23.2 mV for a 10-fold change in [Ca2+]0. These results suggested that the effects of nicotine on enhancing Isi were mediated by the release of catecholamines in myocardium.
Zhu
J X
JX
Department of Physiology, He-nan Medical University, Zhengzhou, China.
Tang
S B
SB
Wu
X Y
XY
Jiang
B
B
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002395:Catecholamines / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology*; D010210:Papillary Muscles / Q000187:drug effects*; D012110:Reserpine / Q000494:pharmacology
D002395:Catecholamines; D009538:Nicotine; D012110:Reserpine