RESUMO
The effect of Pheniramine(Avil), a histaminergic-1 receptor blocking agent presently employed in treating various allergic diseases on pressor actions of norepinephring(NE) and tyramine (TR) was studied in the rabbit. Pheniramine, when given into a femoral vein with a dose(3mg/kg) enough to block H1-receptor, potentiated markedly the pressor responses of NE and TR. The pressor action of NE augmented by pheniramine was not affected by additional adminstration of debrisoquin (Drenergic neuron blocker) or phenelzine(monoamine oxidase inhibitor) or desipramine(U1-uptake blocker), or while potentiated by additional treatment with chlorisondamine(ganglionic blocker)or reserpine(catecholamine depleter). The hypertensive response of NE to phenelzine or desipramine was reinforced significantly by addition of pheniramine, but the response of NE in rabbits treated with reserpine or chlorisondamine or debrisoquin was not influenced by pheniramine-addition. Elevation of blood pressure to TR potentiated by pheniramine was attenuated significantly by reserpine treatment with chlorisondamine made the significant augmentation of pressor action to TR after pheniramine. Tyramine-induced response of blood pressure after pheniramine, but the response of blood pressure to TR caused by phenelzine or desipramine was enhanced markedly by pheniramine-treatment. From the above experimental results, it is thought that the pressor effect of NE and TR potentiated by pheniramine is similar to that of debrisoquin, i.e. the sensitization of effector cell, and that central action of pheniramine can not ruled out.