Association between sympathetic nerve activity and cerebrovascular protection in young spontaneously hypertensive...

The purpose of this study was to determine resting and maximal superior cervical sympathetic nerve activity in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) at five and ten weeks of age as hypertension was developing. Basal cervical sympathetic nerve activity (SNA) of five week SHR was 58 +/- 3 muv* which was significantly elevated over age-matched WKY (SNA = 30 +/- 4 muv, *p less than 0.001) and ten week SHR (SNA = 30 +/- 4 muv, *p less than 0.001) as well as ten week WKY (SNA = 24 +/- 4 muv, *p less than 0.001). Thus, during basal conditions five week SHR nerve traffic was approximately two times that found in age-matched WKY as well as in ten week SHR and WKY. The peak sympathetic nerve activity in response to rapid hemorrhage in five week SHR (215 +/- 16 muv*) was significantly elevated over the maximal response of WKY (140 +/- 23 muv) (*p less than 0.02). Ten week SHR also reached a maximal sympathetic nerve activity (187 +/- 28 muv*) that was significantly elevated over WKY (100 +/- 15 muv) (*p less than 0.02). Thus, both five and ten week SHR had a greater capacity for elevated nerve activity following rapid hemorrhage than age-matched WKY. The elevation in resting cervical sympathetic activity in five week SHR, and the elevated capacity for sympathetic neural response in both five as well as ten week SHR, are consistent with a central nervous system abnormality in SHR that could relate to the previously described protective influence of sympathetic nerves on SHR cerebral blood vessels as hypertension is developing.