Abstract
Histamine can stiumulate the heart by directly interacting with cardiac histamine receptors. In the present study we have investigated the cardiac effects of histamine, 4-methylhistamine (a specific H2-receptor agonist) and 2-pyridylethylamine PEA, a specific H1-receptor agonist] on spontaneously beating right atria and electrically driven left atria and right ventricle strips of the guinea pig. Left atria were driven at 1 Hz and right ventricle strips at 2.5 Hz and at twice the threshold voltage. Histamine and PEA produced a dose-dependent positive inotropic effect on the left atria. The dose-response curves were shifted to the right in a parallel fashion by promethazine (3 x 10(-6)M)+... Burimamide did not affect either dose-response curve. Histamine and 4-methylhistamine had a positive chromnotropic effect on right atria and a positive inotropic effect on right ventricle strips.
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