Slowered turnover of norepinephrine in the brain associated with an acute elevation in blood pressure of rats.

Acute responses of blood pressure and turnover of norepinephrine in the brain to intracisternally injected guanethidine were studied in rats. Systolic blood pressure in guanethidine-treated rats showed a dose-relating rise for over 9 hrs, while norepinephrine contents in cortex-cerebellum, brain stem and heart were not affected. The endogenous norepinephrine in brain samples, however, did not decrease against alpha-methyl-p-tyrosine to result in regression coefficients significantly different from those in the saline-treated group whereas norepinephrine in heart was reduced similarly in the 2 groups, indicating a slowered turnover of norepinephrine selectively in the brain. The results may indicate that the retarded norepinephrine turnover in the brain is causatively related with an acute elevation in blood pressure.