Influence of Water-Immersion Stress on Catecholaminergic Systems in Rat Brain

Kazuhisa Maeda*†, Yoshinori Kamisaki† and Tadao Itoh†

*Department of Neuro-Psychiatry and †Department of Clinicla Pharmacology, Faculty of Medicine, Tottori University, Yonago 683, Japan

The effects of water-immersion restraint stress on noradrenergic nerves in the rat brain were evaluated by measuring catecholamine content, cyclic adenosine 3',5'-monophosphate (cAMP) Ievels and enzyme activity synthesizing catecholamines and cAMP. The stress caused a significant decrease in noradrenaline, and an increase in the dopamine content of the hypothalamus in a manner that was dependent on the duration of stress applied. In animals exposed to 1-h stress, a significant decrease in dopamine-β-hydroxylase (DBH) activity, and an increase in aromatic L-amino acid decarboxylase (AAAD) activity were observed. Stress longer than I h caused no significant changes in DBH and AAAD activity. Although no significant changes in cAMP Ievels were detected throughout the whole brain of stressed rats, adenylate cyclase activity significantly increased. These results suggest that water-immersion restraint stress may promote a release of both noradrenaline and DBH from noradrenergic nerve terminals, and that these releases may consequently potentiate AAAD activity in order to restore the depleted noradrenaline, thereby reflecting an increase of dopamine levels in the brain.

Key words: adenylate cyclase; aromatic L-amino acid decarboxylase; dopamine-β-hydroxylase; stress

RETURN