Elevated tyrosine hydroxylase mRNA levels in medulla oblongata of spontaneously hypertensive rats.

The present study has investigated the expression of tyrosine hydroxylase (TH) mRNA and its activity in medulla oblongata of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The TH mRNA levels were determined by Northern blot and dot blot analyses. The TH activity and the expression of TH mRNA in medulla oblongata of SHR were significantly higher than those of WKY. These results suggest that the hypertension of SHR may be related to the high activity of TH due to the high level of TH mRNA which increases norepinephrine levels in the medulla oblongata.