Differential expression of nNOS mRNA and protein in the nucleus tractus solitarii of young and aged Wistar–Kyoto and spontaneously hypertensive rats

OBJECTIVE: To examine neuronal nitric oxide synthase (nNOS) mRNA and protein in the nucleus tractus solitarii (NTS) and paraventricular hypothalamic nucleus (PVN) of Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) during their life span. METHODS: By means of in situ hybridization and immunohistochemistry, we evaluated nNOS mRNA and protein in the NTS and PVN of 15-day- and 1-, 2-, 4-, 8- and 12-month-old SHR and WKY rats. RESULTS: Two patterns of nNOS expression were observed in two subnuclei of the NTS: medial (NTSm) and central (NTSce). NTSce of the SHR exhibited higher nNOS mRNA and protein expression in all ages analyzed when compared to the age-matched WKY. Increased amounts of nNOS mRNA and protein were seen in the NTSm only during the early life of SHR (15 days to 4 months) when compared to WKY, suggesting a special role of this circuitry before the establishment of hypertension. No changes were seen in nNOS mRNA and protein expression in the PVN of the SHR in comparison to the WKY in all periods. nNOS analysis during the life span showed either a decrease or no change in nNOS mRNA expression in NTS or PVN associated with increased nNOS protein at some analyzed periods, suggesting the differential regulation of nNOS mRNA and protein during aging. CONCLUSIONS: Data suggest that different NTS subnuclei exhibit nNOS changes in different phases of the life of SHR and this might be important during the development of hypertension in these animals.