[Study of species differences on chemical sympathectomy: rats and guinea pigs]

Chemical sympathectomy induced by guanethidine or 6-hydroxydopamine (6-OHDA) and reserpinization were investigated by their influences on the cardiovascular system in urethane-anesthetized rats and guinea pigs and on nerve endings in the atrium or aorta and adrenaline-containing granules in the adrenal medulla. In rats, guanethidine and 6-OHDA significantly lowered the basal blood pressure, but reserpine did not. In guinea pigs, none of them affected the basal blood pressure, and with the exception of the potentiation of adrenaline-induced pressor responses, the influences of all 3 drugs on adrenaline- and tyramine-induced responses in blood pressure and heart rate were weaker than those in rats, but influences of treatments with guanethidine for 1 week were more striking than those for 5 weeks. There were significant differences between rats and guinea pigs in classified forms of nerve endings in the right atrium and of adrenaline-containing granules in the adrenal medulla or differences in the influences on the adrenal medulla by all 3 drugs. Only 6-OHDA induced injury in rat atrium. The above results suggest that there are species differences between rats and guinea pigs, not only in the chemical sympathectomized animals but also in the normal condition and that the pharmacodynamic effect of chemical sympathectomy is more prominent in rats than in guinea pigs.