Differential mRNA expression of cyclic‐AMP response element binding protein and neuronal nitric oxide synthase in the dorsal medulla of salt‐sensitive and salt resistant Dahl rats

Abstract

The purpose of this study was to examine the mRNA levels of cyclic-AMP response element binding protein (CREB) and neuronal nitric oxide synthase (nNOS) in the dorsal medulla of Dahl salt sensitive (DS) and salt resistant (DR) rats. The rats were fed either a regular salt (0.2% NaCl) or a high salt (8% NaCl) diet for three weeks (n= 5 /group). Mean arterial pressure was increased in DS rats (174±10 [mean±SE]) compared to DR rats on high salt (105±4). The animals were sacrificed by decapitation; brain was immediately removed and kept in RNA Later. Gracile nucleus (GR) and nucleus of tractus solitarius (NTS) regions were isolated by micropunch technique from brain sections. Total RNA was isolated and quantitative real time PCR was carried out. mRNA levels of CREB in the NTS region were increased 1.67-fold in DS rats and 1.6-fold in DR rats with high salt compared with the regular salt (p<0.05). nNOS mRNA increased 2.7-fold in both high salt DS and DR rats compared to the normal salt rats (p=0.09). In the GR regions, high salt tended to increase mRNA levels of CREB and nNOS in both DS and DR rats. The results show that high salt diet increases mRNA levels of CREB and nNOS in the NTS region, possibly in the GR region, of DR and DS rats. We conclude that salt loading induces up- regulation of CREB and nNOS mRNA in the dorsal medulla which may contribute to central regulation of the circulation during salt metabolism. Supported by NIH (AT002478, HL04447, and AT00450) to S. Ma.