Catecholamine Turnover in the Central Nervous System and Effects of Clonidine and Guanfacine

Abstract

Noradrenaline and dopamine levels in the cerebrum and cerebellum (C & C) and noradrenaline levels in the brain stem (BS) were higher, and the rate of diethyldithiocarbamate (DDC)-induced disappearance of noradrenaline in C & C and BS was lower in young spontaneous hypertensive rat (SHR) than in Wistar Kyoto rats (WKY). In the adult SHR and WKY noradrenaline and dopamine levels in C & C and BS were not different from each other. The noradrenaline level in BS of DOCA-hypertensive rats (DHR) was higher than that of age-matched Wistar Imamichi rats (WI), while noradrenaline and dopamine levels in C & C were not significantly different. In adult SHR and DHR, noradrenaline disappearance in C & C was slower than in WKY and WI, respectively, while faster in BS of SHR and DHR than of WKY and WI, respectively. In adult SHR, Clonidine and guanfacine produced no change in noradrenaline and dopamine content of the C & C, BS and corpus striatum (CS) when compared to WKY; however, they caused marked dose-dependent retardations of noradrenaline disappearance in C & C and BS following DDC and of α-methyl-p-tyrosine-induced disappearance of dopamine in CS. These results indicate the possibility that a higher level and an augmented disappearance of noradrenaline in BS are related to the development of hypertension.