FOOT SHOCK-INDUCED CHANGES IN BLOOD AND BRAIN-SEROTONIN AND RELATED SUBSTANCES IN RATS

The effects of electric foot shock on peripheral and central serotoner gic systems in rats have been studied. We have focused on the time cou rse alterations with particular attention being paid to changes in 5-H T, 5-HIAA, tryptophan concentrations and 5-HIAA/5-HT ratios in blood a nd various parts of the brain, observed within 1 h following stress ap plication. Blood and brain (7 regions) samples were taken immediately after electric foot shock, 30 min, 1 and 24h later. In the blood stres s induced a rise in tryptophan level as well as rises in 5-HT, 5-HIAA levels and 5-HIAA/5-HT ratio within 1 h following stressful treatment. Tryptophan concentration was found to be increased in every part of t he brain within 1 h after electric foot shock application. In striatum it remained higher even after 24 h. 5-HT level showed a significant r ise only in medulla, while hypothalamus was the sole region where a fa ll in 5-HT was found. In other parts of the brain 5-HT level remained unaffected by stress. 5-HIAA content increased in almost every brain a rea studied except cerebellum and striatum. 5-HIAA/5-HT ratios shared the same pattern of changes. Briefly, foot shock altered 5-HT turnover in various brain regions, in particular within the first hour followi ng stess application, whereas delayed response to stress was rarely ob served. Increased brain tryptophan level seems to be necessary to cope with the enhanced 5-HT metabolism caused by stress, reflecting as a r ise in 5-HIAA concentration and 5-HIAA/5-HT ratio.