Effects of cord section and pithing on spontaneously hypertensive rats

In spontaneously hypertensive rats and normotensive control rats the spinal cord was transected between the vertebrae C7 and Th 1 under ether anesthesia. When the animals recovered from anesthesia in two hours, the blood pressure was significantly higher in the hypertensive rats, indicating that the hypertensive factors are not confined to the supraspinal centers. The blood pressure was also significantly higher in spontaneously hypertensive rats than in normotensive control rats even after pithing the spinal cord below the vertebra of Th 1. In either case subsequent pentobarbital anesthesia abolished the significant difference in pressure between the two groups of rats. The blood pressure after either cord section or pithing tended to increase with age in spontaneously hypertensive rats but not in normotensive control rats. These findings indicate the presence of certain age-dependent peripheral hypertensive factors which are susceptible to pentobarbital and probably myogenic in nature.