CHRONIC ACTIVATION OF BRAIN-AREAS BY HIGH-SODIUM DIET IN DAHL SALT-SENSITIVE RATS

To map changes in neuronal activity in the brains of Dahl salt-sensiti ve (Dahl S) vs. salt-resistant (Dahl R) rats by high-sodium diet, we u sed immunohistochemical detection of Fra-Like proteins as a marker for long-term neuronal activation. Compared with Dahl R rats during regul ar sodium intake, Dahl S rats showed modestly higher expression of Fra -like immunoreactivity (Fra-LI) in the supraoptic nucleus, anterior hy pothalamic area (AHA), central gray, and nucleus of solitary tract (NT S) at 5, 6, and 9 wk of age but clearly elevated Fra-LI in the magnoce llular part of the paraventricular nucleus (PVN) at 6 wk of age (but n ot at 5 and 9 wk). In the median preoptic nucleus (MnPO) Fra-LI was lo wer at 9 wk of age and no differences were observed in the parvocellul ar PVN and subfornical organ in Dahl S vs. Dahl R rats on regular sodi um intake. Compared with Dahl S rats on a regular-sodium diet, Dahl S rats on a high-sodium diet from 4 to 9 wk of age had significantly inc reased blood pressure and experienced transient activation of magnocel lular PVN and MnPO and virtually no changes in the activity of the par vocellular PVN, AHA, and NTS. In contrast, Dahl R rats showed marked a ctivation in the magnocellular PVN after 1 and 2 wk on a high-sodium d iet compared with Dahl R rats on a regular-sodium diet. The present st udy demonstrates that Dahl S rats show differential activation of brai n areas participating in regulation of osmotic and cardiovascular home ostasis during development of sodium-sensitive hypertension.