Adenovirus-mediated nitric oxide synthase gene transfer into the nucleus tractus solitarius in conscious rats

The nucleus tractus solitarius (NTS) of the brainstem is an important site for the regulation of sympathetic nerve activity. In the brain, nitric oxide (NO) has been shown to reduce blood pressure by inhibiting sympathetic nerve activity. However, most studies were performed in an acute state of anesthesia. Therefore, we developed a technique to increase the local production of NO in vivo by the transfer of endothelial NO synthase (eNOS) gene into the NTS. Adenovirus vectors encoding either the beta-galactosidase gene (Adbetagal) or the eNOS gene (AdeNOS) were infected into the NTS. In the Adbetagal-infected rats, the local expression of beta-galactosidase was confirmed by X-Gal staining, and beta-galactosidase activity was quantified using a colorimetric assay. In the AdeNOS-infected rats, the local expression of eNOS was confirmed by immunohistochemistry and Western blot analysis. Production of NO was measured by in vivo microdialysis. Blood pressure and heart rate were monitored by a radiotelemetry system in a conscious state. In the AdeNOS-infected rats, blood pressure and heart rate significantly decreased from d 5 to d 10, and then gradually recovered over time. These methods should be useful in examining the local effect on cardiovascular function of a particular substance produced by a specific gene in the brain.