Endothelial NO Synthase Activity in Nucleus Tractus Solitarii Contributes to Hypertension in Spontaneously Hypertensive Rats

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Abstract
NO is implicated as a major modulator of central nervous circuits regulating cardiovascular activity. Based on previous data, we hypothesized that overactivity of endothelial NO synthase (eNOS) within the nucleus tractus solitarii (NTS) could contribute to the hypertension in the spontaneously hypertensive rat (SHR). Using real-time PCR, we found that endogenous eNOS mRNA was greater in the NTS of mature, but not juvenile prehypertensive SHRs compared with aged-matched Wistar Kyoto (WKY) rats. To test the functional significance of this, we chronically blocked eNOS activity in the NTS in the adult SHR by in vivo adenoviral-mediated gene transfer of a dominant-negative form of eNOS; data were compared with WKY rats. This resulted in a fall in arterial pressure in the SHR but not WKY rats. In both rat strains, cardiac baroreceptor reflex gain and the high-frequency spectral component of heart rate variability increased. Thus, endogenous eNOS activity in the NTS plays a major role in determining the set point of arterial pressure in the SHR and contributes to maintaining high arterial blood pressure in this animal model of human hypertension.

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