Effects of long-term cerebral ischemia caused by bilateral carotid artery ligation on the acceleration or the development of hypertension in spontaneously hypertensive rats (SHR) or Wistar-Kyoto rats (WKY).

Bilateral carotid artery ligation (BCL) was performed with one week interval between the each operation in male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) aged 4 months. BP rose immediately after unilateral carotid artery ligation (UCL) and BCL in both WKY and SHR due to carotid sinus reflex. Once returning to preoperative levels after both UCL and BCL, BP of SHR and WKY increased again gradually one and 4 months after BCL and thereafter, respectively. BP was significantly higher than that in the controls of each strain, and the BP increment was significantly greater in SHR than in WKY. A significant regional cerebral blood flow (rCBF) increase on the contralateral side of carotid ligation was observed in SHR in contrast to a little change in that of WKY and a reduction of rCBF after BCL was significantly greater in SHR than in WKY. Behavioral activities in SHR were also reduced after BCL. Cerebral edema with nerve cells damage was recognized in SHR. In contrast, little change was found in WKY. On the other hand, upper cervical sympathectomy attenuated convulsive seizures after BCL more markedly in SHR, which survived longer than non-denervated SHR. These results suggest that chronic mild cerebral ischemia caused by BCL with one week interval accelerates the development of severe hypertension in SHR and developed mild hypertension in WKY. Sympathetic innervation might play much more important role in collateral circulation through the vertebrobasilar system in SHR.