The action of eledoisin on the systemic arterial blood pressure of some experimental animals.

The blood pressure response following parenteral administration of eledoisin varies conspicuously from one animal species to another. In the dog the polypeptide elicits a clear hypotension under all experimental conditions. Eledoisin is active at extremely low dose levels and hypotension is not appreciably affected by previous treatment with atropine, sympatholytic drugs, ganglion-blocking agents or reserpine. Eledoisin potently antagonizes the pressor effects of catechol amines and of angiotensin. Longlasting hypotension can be obtained by intravenous infusion or subcutaneous injection of the polypeptide. The mechanism of action of eledoisin in the dog is believed to be chiefly peripheral. The rabbit, the guinea-pig and the cat behave like the dog in the type but not in the intensity of their blood-pressure response to eledoisin. The rat gives variable responses to the polypeptide. After treatment with a ganglion-blocking drug, or in the pithed rat, a rise in blood pressure is the predominant effect. In the anaesthetized chicken eledoisin generally produces a diphasic response, but in the decapitated animal only hypertension. This last effect is believed to depend largely, if not entirely, on the release of catechol amines from body stores. The dog blood pressure may be used for the assay of eledoisin; suitable results may also be obtained from the pressor effects in decapitated chickens.