Levels of immunoreactive angiotensin II in microdissected nuclei from adult WKY and SH rat brain.

Levels of immunoreactive angiotensin II (ANG II) were measured by radioimmunoassay in microdissected nuclei from the brain of the spontaneously hypertensive rat (SHR) and its normotensive control, the Wistar Kyoto rat (WKY). The nuclei assayed included the paraventricular nucleus of the hypothalamus (PVH), locus coeruleus (LC), nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus nerve (DMN of X) and the A1 region of the medulla. Sections of cerebral and cerebellar cortex were used as controls. Levels of immunoreactive ANG II ranged from 0.24 nmoles/g protein to 0.93 nmoles/g protein, with SHR brain containing significantly higher levels than WKY brain in the PVH and NTS. Although LC and DMN of X in the SHR brain contained higher levels of immunoreactive ANG II than WKY brain, the difference was not significant. No significant difference was found in the A1 region between the two species, and no detectable ANG II immunoreactivity was found in cerebral or cerebellar cortex. Since each of the nuclei studied has been implicated in the neural control of cardiovascular function, the increased levels of immunoreactive ANG II in the SH rat brain nuclei indicates a possible role for ANG II in the pathophysiology of hypertension in the SHR model.