Pattern of neuronal activation during development of hypertension in Dahl S rats

Central neuronal mechanism play a major role in the development of hypertension in Dahl S rats In order to identify neuronal populations involved, immunohistochemical detection of Fra-like immunoreactivity (Fra-LI) was used to identify neurons activated by high sodium diet in Dahl S and R rats Groups of Dahl S and R rats (4 weeks old) received either regular (0.5% NaCl, RNa) or high sodium (8% NaCl, HNa) diet for 1, 2 or 5 weeks Subsequently, rats were perfused and brains processed for detection of Fra-LI using an antibody which recognizes Fos, FosB, Fra-1 and Fra-2. Fra-LI expression was quantified in osmosensitive and BP-regulating areas. In the MnPO, HNa diet induced significant increases in Fra-LI in R (18±1) vs S (9±1) particularly at 5 weeks On RNa diet, expression of Fra-LI was undetectable in SFO. However. HNa significantly increased Fra-LI at 2 weeks (R, 10±1 and S, 13±1) and 5 weeks (R, 6±1 and S, 8±1) in this area. In the parvocellular PVN, Fra-LI did not differ between Dahl S and R rats on both diets. In contrast, HNa significantly increased Fra-LI in magnocellular PVN which was more pronounced in R (46±2) vs S (11±1) particularly after 2 weeks In the AHA, HNa diet significantly increased Fra-LI in S (9±1) vs R (4±1) at 5 weeks. Our results indicate that Dahl S and R rats significantly differ in the activation of specific nuclei by high sodium diet.