The chronotropic and inotropic effects of tetramethylpyrazine (TMPZ) obtained from the stem of Jatropha podagrica HOOK (Euphorbiaceae) have been investigated on guinea-pig isolated atria. TMPZ caused negative chronotropic and inotropic responses on the isolated atria of guinea-pigs. These TMPZ - induced negative chronotropic and inotropic responses were resistant to the action of atropine. Prior administration to the bath fluid of TMPZ also antagonized the positive chronotropic and inotropic effects of isoprenaline, noradrenaline and calcium on the tissue preparations. It is concluded that TMPZ probably exerts a non-specific inhibitory effect on the isolated cardiac muscles examined, and that this non-specific depressant action on the myocardium might have contributed, at least in part, to the observed in vivo depressor (blood pressure lowering) effects of the amide alkaloid reported earlier.
Jatropha podagrica - Euphorbiaceae - Amide Alkaloid - Tetramethylpyrazine - Guinea-pig Isolated Atria - Negative Chronotropic and Inotropic Effects - Hypotensive Action - Non-specific Cardiac Depression
