Presynaptic modulation by endogenous ouabain-like substances of noradrenaline release from blood vessels.

The effect of an endogenous ouabain-like compound (OCL) and of ouabain was studied on [3H]noradrenaline release and on the tension of rabbit pulmonary arterial strip. Similarly to ouabain, the OLC enhanced release of [3H] NA in resting and in stimulated condition. Moreover, in the presence of OLC and ouabain, the tension of the rabbit artery increased gradually and the contraction evoked by electrical stimulation was potentiated. It is suggested that this mechanism might be involved in the physiological regulation of blood pressure or in the genesis of hypertension.