Patterns of neuronal activation during development of sodium sensitive hypertension in SHR

The effects of regular (RNa) or high (HNa) sodium diet for 3, 7, and 14 days on Fra-like immunoreactivity (Fra-LI) in the brains of Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were examined using an antibody that recognizes all known members of the Fos family (Fos, Fos-B, Fra-1, and Fra-2). Two weeks of HNa significantly exacerbated hypertension in SHR but had no effects in WKY. On RNa, compared with WKY, SHR showed higher Fra-LI in the median preoptic nucleus, supraoptic nucleus, both parts of the paraventricular nucleus, nucleus of the solitary tract, and central gray. Fra-LI in the subfornical organ did not differ between the two strains. On RNa, Fra-LI in the anterior hypothalamic area could be detected only in WKY. In osmoregulatory areas, HNa diet increased Fra-LI in both SHR and WKY to comparable extents, but in the median preoptic nucleus, Fra-LI was increased to a greater extent in SHR. HNa produced smaller increases in the subfornical organ of SHR compared with WKY. In both the parvocellular and magnocellular paraventricular nuclei, increases in Fra-LI by HNa were more pronounced in SHR than in WKY. In the anterior hypothalamic area, Fra-LI could no longer be detected in WKY on HNa, whereas it appeared in SHR. HNa increased Fra-LI in the NTS and central gray to similar levels in WKY and SHR. These results indicate that WKY and SHR differ in the pattern of neuronal activation accompanying maturation on RNa. HNa activates neurons in a number of brain areas, and the pattern of these changes also differs between WKY and SHR.