Effects of chemical sympathectomy on hypertension and stroke in stroke-prone spontaneously hypertensive rats.

Neonates of male stroke-prone spontaneously hypertensive rats (SHRSP) were treated with 6-hydroxydopamine (6-OHDA) on two different schedules. Peripheral sympathectomy, which was evaluated by the pressor response to exogenous noradrenaline (NA) or by the decrease in NA content of the spleen, was more evident in the NB-8 group (treated on 8th and 15th day after birth) than in the NB-1 group (treated at 6, 24 and 72 h after birth). The reduction of the NA content in the cerebral cortex was more prominent in the NB-1 group than in the NB-8 group. The blood pressure from 7 to 23 weeks of age was lower in the treated groups: NB-8 less than NB-1 less than control. Therefore, the reduction of blood pressure in the treated groups could be related to the severity of peripheral sympathectomy. The incidence of sroke was also lower in the treated groups: 38, 11 and 0% in the control NB-1 and NB-8 groups, respectively. Loading with 1% NaCl solution from 11 weeks of age enhanced the rise in blood pressure and increased the incidence of stroke in each group of rats: 100, 20 and 40% in the control. NB-1 and NB-8 groups, respectively. However, the onset of stroke after exhibiting a severe hypertension (greater than 200 mmHg) was delayed in the treated groups. It seems that the activated tone in the peripheral sympathetic nerve is likely to participate in the development of spontaneous hypertension. In addition to the high blood pressure level, the activated tone of sympathetic nerve innervating the cerebral vasculature may be partly involved in the development of stroke in the new strain of the SHR rats, SHRSP.