Regional responses of rat brain noradrenergic neurones to acute intense stress

Contents of noradrenaline (NA) and its principal metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in six brain regions of the rat were monitored simultaneously during 180 min of acute intense stress, i.e., electric tail shock under immobilization. In the hypothalamus and amygdala, NA contents decreased rapidly, and subsequently remained at the decreased levels while MHPG-SO4 contents increased progressively. The hippocampus and cerebral cortex showed more delayed changes in NA and MHPG-SO4 contents than the above regions. In the pons+med. obl., no decreases of NA contents were observed at any time, but MHPG-SO4 contents increased significantly. Neither NA nor MHPG-SO4 content changed significantly in the basal ganglia except for a transient increase of NA. These results suggest that, during acute intense stress, each brain region responds differently and the NA content is maintained at a decreased level despite continuously enhanced release of the amine.