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 1 4 days on Fra-like immunoreactivity (Fra-LI) in the brains of Wistar-K yoto rats (WKY) and spontaneously hypertensive rats (SHR) were examine d using an antibody that recognizes all known members of the Fos famil y (Fos, Fos-B, Fra-1, and Fra-2). Two weeks of HNa significantly exace rbated hypertension in SHR but had no effects in WKY. On RNa, compared with WKY, SHR showed higher Fra-LI in the median preoptic nucleus, su praoptic nucleus, both parts of the paraventricular nucleus, nucleus o f the solitary tract, and central gray. Fra-LI in the subfornical orga n did not differ between the two strains. On RNa, Fra-LI in the anteri or hypothalamic area could be detected only in WKY. In osmoregulatory areas, HNa diet increased Fra-LI in both SHR and WKY to comparable ext ents, but in the median preoptic nucleus, Fra-LI was increased to a gr eater extent in SHR. HNa produced smaller increases in the subfornical organ of SHR compared with WKY. In both the parvocellular and magnoce llular paraventricular nuclei, increases in Fra-LI by HNa were more pr onounced 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 i n WKY and SHR. These results indicate that WKY and SHR differ in the p attern of neuronal activation accompanying maturation on RNa. HNa acti vates neurons in a number of brain areas, and the pattern of these cha nges also differs between WKY and SHR.