Marked enhancement of noradrenaline turnover in extensive brain regions after activity-stress in rats

Male Wistar rats were exposed to a 5-day activity-stress procedure wherein animals were housed in running-wheel activity cages and fed for only 1 hr each day (wheel-housed/food-restricted rats). This activity-stress procedure produced marked elevation in levels of the major metabolite of noradrenaline (NA), 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO₄), in eight brain regions, while a reduction of NA level occurred in several of these brain regions. These rats also exhibited excessive running activity and developed severe gastric glandular ulcers. Rats fed ad lib and housed in activity cages (wheel-housed/ad lib-fed) and rats housed in standard individual cages and which received either 1-hr daily feeding (control cage-housed/food-restricted) or ad lib feeding (control cage-housed/ad lib-fed) showed neither significant changes in brain NA metabolism nor gastric ulcers. These results suggest that the interaction of a restricted feeding regimen and an increase running wheel activity caused marked enhancement of NA turnover in several brain regions, which is one of the neurochemical mechanisms underlying the physiological and behavioral changes produced by the activity-stress paradigm.