[Enhancement effect of tetramethylpyrazine on slow inward current in guinea pig papillary muscles].
Tetramethylpyrazine (TMP) could potentiate the force of contraction and increase the action potential duration (APD) of isolated guinea pig papillary muscles in a dose-dependent manner. Similar effects were also observable in BaCl2 or histamine-induced contraction and the accompanied slow action potential (SAP). In fact, contraction and SAP could also be induced by TMP itself at 3.0 mmol/L concentration and antagonized by verapamil (1 mumol/L) within 10 min. In the presence of propranolol or in experiments carried out in catecholamine-depleted (reserpine 2.5 mg/kg, i.p. 15 h prior to the experiment) muscles, TMP was unable to induce SAP and contraction. These results suggested that the effects of TMP on enhancing Isi were mediated by the release of catecholamine in myocardium.
Bai
Q
Q
Department of Physiology, Henan Medical University, Zhengzhou.
Tang
S B
SB
D000200:Action Potentials; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000502:physiology; D011719:Pyrazines / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011719:Pyrazines; C017953:tetramethylpyrazine