An increase in the sympathoadrenal medullary function in stroke-prone spontaneously hypertensive rats under anesthetized and resting conditions.

Sympathoadrenal medullary functions were investigated in stroke-prone spontaneously hypertensive rats (SHR-SP) and in control normotensive Wistar-Kyoto rats (WKY) under halothane-anesthetized and resting conditions. The mean frequency of the spontaneous efferent activity of a single adrenal sympathetic nerve fiber was 1.08 +/- 0.11 impulses/s in WKY and 2.82 +/- 0.24 imp/s in SHR-SP, indicating a much higher level in SHR-SP than in WKY. The secretion rates of both adrenaline and noradrenaline from the adrenal gland were higher in SHR-SP than in WKY. The secretion rates of adrenaline and noradrenaline in WKY were 16.8 +/- 3.0 and 1.70 +/- 0.09 ng/kg X min, respectively, while those in SHR-SP were 36.7 +/- 3.9 and 2.56 +/- 0.18 ng/kg X min, respectively.