Alpha-adrenoceptor-blocking properties of some trypanocidal diamidines.

A series of trypanocidal diamidines and diimidazolines known to cause severe hypotension were tested for their alpha-adrenoceptor blocking properties in vitro. At the postsynaptic alpha 1-receptor of the guinea-pig aorta in vitro all compounds at doses of 0.5 to 50 mumol/l showed weak antagonistic effects against noradrenaline. Similar results were obtained at the presynaptic alpha 2-receptor of the rat vas deferens.