[Effects of the polyamines putrescine, spermidine and spermine on the hypertensive action of norepinephrine in anesthetized dogs].

In anesthetized and vagotomized dogs, we investigate the associative effects on blood pressure of norepinephrine (NE) with the three polyamines putrescine (Pt), spermidine (Sd) and spermine (Se). Experimental series were performed under beta adrenergic blockade (propranolol 0.5 mg/Kg, iv.), alpha adrenergic blockade (phenoxybenzamine 15 mg/Kg, iv.), and under calcium antagonistic action (verapamil 0.3 mg/Kg, iv.). The three polyamines induced a potentiation on the hypertensive effect of NE, they change the dose/response curve to the left side in a potency rank of Se greater than Sd greater than Pt. Such potentiation was not different when a beta adrenergic blockade or calcium antagonism was present; however phenoxybenzamine neutralized it. On the other side, polyamines had a hypotensive effect when were administered alone to the animals. Such effect is related to a histamine releasing properties of the polyamines, and was abolished by previous administration of anihistaminic agents chlorpheniramine (5 mg/kg, iv.) and cimetidine (20 mg/Kg, iv.). In conclusion our results indicate that the potentiation of the hypertensive effect of NE by polyamines, could be attained through a mechanism which involves the alpha adrenergic receptors of the vascular smooth muscle but is not related to the calcium channels that show voltage dependence.