[Effects of lobeline on slow action potential and force of contraction of guinea pig papillary muscle].
Intracellular microelectrode techniques were used to study the effects of N1-receptor agonist lobeline on the slow action potentials (SAP) and the force of contraction (FC), induced by histamine, BaCl2 and aminophylline, in catecholamine-depleted guinea pig papillary muscles in the presence of an M-cholinergic receptor antagonist atropine (3 mumol.L-1). In these preparations lobeline (1-64 mumol.L-1) suppressed, in a dose-dependent manner, the action potential amplitude (APA), the action potential duration (APD), the maximal upstroke velocity (Vmax) and FC. Elevation of calcium concentration outside the myocardiac cells to 3.6 mmol.L-1 antagonized the effects of lobeline in different degrees. These results suggest that the lobeline inhibits the slow inward current Isi of myocardiac cells.
Zhang
R L
RL
Department of Physiology, He-nan Medical University, Zhengzhou, China.
Tang
S B
SB
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D008120:Lobeline / Q000494:pharmacology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000502:physiology*
D008120:Lobeline; D002118:Calcium