Enhanced sympathetic activity in young spontaneously hypertensive rats is not the trigger mechanism for genetic hypertension.

In young, spontaneously hypertensive rats (SHR), a preganglionic, nerve-dependent, elevation of choline acetyltransferase (ChAc) and tyrosine hydroxylase (TH) activities was found in celiac ganglia as compared with those in young, normotensive Kyoto Wistar rats, that was not present in superior cervical ganglia, stellate ganglia and adrenal glands. The rise in both enzyme activities in the celiac ganglion disappeared in adult SHR. An elevation of plasma norepinephrine and dopamine beta-hydroxylase levels found in prehypertensive SHR, a probable indication of peripheral sympathetic activation, disappeared after the bilateral removal of the celiac ganglion. However, ganglionectomy did not change the subsequent development of hypertension. These results indicate that the faster maturation of the celiac ganglion and the end organs it innervates in yount SHR are causally related to the activation of the peripheral sympathetic nervous system. The peripheral sympathetic activation in young SHR is regarded as a warning sign but this does not trigger the development of hypertension.