COMPARISON OF STRESS-INDUCED CHANGES IN NORADRENERGIC AND SEROTONERGIC NEURONS IN THE RAT HIPPOCAMPUS USING MICRODIALYSIS

The effects of stress on the serotonergic and noradrenergic projection to the hippocampus were compared in freely moving rats using microdia lysis. Stress-induced changes in 5-hydroxytryptamine (5-HT), noradrena line and their metabolites 5-hydroxyindoleacetic acid (5-HIAA) and 3,4 -dihydroxyphenylacetic acid (DOPAC) were measured in the presence of t heir respective uptake blockers. Local infusion of tetrodotoxin and re placement of Ca2+ with Cd2+ were used to test dependence on impulse tr affic. A 5 min tail pinch or 10 min restraint stress increased 5-HT, 5 -HIAA, noradrenaline and DOPAC levels. A subcutaneous saline injection produced an increase in 5-HT and DOPAC but not noradrenaline or 5-HIA A. Although alpha(2) adrenoceptor agonists and antagonists produced ch anges in the baseline values of noradrenaline and DOPAC, they had litt le or no effect on stress-induced changes. Both the abolition of impul se traffic and its enhancement by stress had a greater effect on trans mitter than on metabolite levels. Although the responses to stress of the noradrenergic and serotonergic pathway showed many similarities, t here was evidence for their activation by separate pathways.