Indices of sympathetic activity in the sinoaortic-denervated hypertensive rat

Blood pressure and circulating levels of norepinephrine (NE), epinephrine (Epi), and dopamine-beta-hydroxylase (DBH) were measured sequentially in sinoaortic-denervated (SAD) Wistar rats and in sham-operated (SO) rats. Systolic tail pressure, plasma NE and E, and plasma DBH all increased significantly within 2 days in SAD rats. In separate studies of rats with indwelling arterial catheters, arterial pressure and plasma NE and DBH were increased in SAD rats in home cages; restraint caused similar increases of pressure and catecholamines in both groups. Systolic pressure remained increased up to 4 mo and plasma DBH for 10 wk in SAD rats; plasma NE and E, however, declined by 3 wk and thereafter remained close to values of SO rats. Additionally, DBH was increased in heart, mesenteric blood vessels and adrenal glands of SAD rats up to 6 wk; tissue monoamine oxidase activity was also increased up to 4 mo. These findings suggest that activation of the sympathetic nervous system initiates and probably sustains hypertension in SAD rats up to 6 wk after operation; thereafter some other mechanism(s) sustains the hypertension.