Metabolism of 3H-catecholamines in the brain of spontaneously hypersensitive rats (SHR) after running stress.

The influence of stress on the metabolism of adrenaline (A) and noradrenaline (NA) in the prosencephalon (PC) and rhombencephalon (RC) of SHR and normotensive Wistar rats (WR) was studied. After intraperitoneal injection of 3H-tyrosine, radioactivity of 3H-adrenaline (3H-A), 3H-noradrenaline (3H-NA), total 3H-3-methoxy-4-hydroxyphenylglycol (3H-MHPG), total 3H-3,4-dihydroxyphenylglycol (3H-DHPG) and 3H-vanillylmandelic acid (3H-VMA) was measured in PC and RC of SHR and WR, non-stressed or subjected to running stress. Stress induced a significant decrease of 3H-A level in PC and RC of 8-week-old SHR while no stress-related changes in 3H-NA level were found in either part of the brain of SHR. In RC, 3H-A level was lower in older than in younger non-stressed SHR and decreased further after stress. In all SHR, stress enhanced formation of total 3H-MHPG and/or 3H-DHPG in PC, while increased 3H-VMA level was found only in PC of 24-week-old and in RC of 8-week-old stressed SHR. The results suggest that the decrease of the level of 3H-A in the brain of SHR is involved in their reaction to stress and may depend on increased metabolism mainly to glycols but also to VMA. The lower 3H-NA and 3H-A levels in the prosencephalon of non-stressed young and older SHR, concomitant with unaltered or elevated formation of their metabolites, may suggest higher release of the transmitters involved in the pathogenesis of spontaneous hypertension.