Differentiation of H10and H2-receptors mediating positive chronoand inotropic responses to histamine on atrial preparations of the guinea-pig
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- Reinhardt, D., Wagner, J. & Schümann, H.J. Agents and Actions (1974) 4: 217. doi:10.1007/BF01965222
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The positive chronotropic effect in spontaneously beating guinea-pig atria was competitively blocked by burimamide, but not by promethazine.
On the other hand, promethazine proved to be a potent antagonist against the positive inotropic response elicited by histamine on the electrical stimulated (2 Hz) left guinea-pig atrium, whereas burimamide was ineffective.
The positive inotropic response to histamine on the right atrium was affected by both antihistaminic drugs investigated. It should, however, be stressed that the blocking efficacy of both antagonists was less pronounced than that evoked by burimamide on the chronotropic and by promethazine on the inotropic effect on right and left atrium, respectively.
These results suggest that on guinea-pig heart the positive chronotropic effect elicited by histamine is mediated by ‘burimamide sensitive’ H2-receptors, whereas the positive inotropic effect evoked by histamine is mediated by ‘promethazine sensitive’ H1-receptors. The observation that the positive inotropic effect of histamine on the spontaneously beating right atrium could be antagonized by both types of antihistamines favours the view that part of the positive inotropic response to histamine on this preparation is due to a positive frequency-force relationship (Bowditch-Treppe).