INFLUENCE OF REPEATED EXPERIENCE OF VICTO RIES AND DEFEATS IN DAILY AGONISTIC CONFRONTATIONS ON BRAIN SEROTONERGIC ACTIVITY IN MALE-MICE

Serotonin (S-HIT) and 5-hydroxyindoleacetic acid (5-HIAA) levels, tryp tophan hydroxylase (TPH) activity, and 5-HT1A receptor binding were st udied in brain areas of male mice after repealed experience of victori es (winners) acid defeats (losers) in daily male confrontations. A dec rease in the TPH activity in midbrain and its decrease in hypothalamus were shown in winners in comparison with controls. The victory experi ences were accompanied by a pronounced increase of B-max of 5-HT1A rec eptors in the frontal cortex and decrease of K-d in the hypothalamus. Repeated defeats in social confrontations were accompanied by an incre ase in S-MT level in the amygdala acid increase of 5-H1AA/5-HT index i n the hippocampus in comparison with controls. A decrease of B-max in the hypothalamus and of K-d of 5-HT1A receptors both in the frontal co rtex and hypothalamus was shown in losers as compared to controls. An increase in TPH activity under the influence of repeated defects was s hown in striatum and hypothalamus. The obtained evidence point to spec ific changes in serotonergic activity which characterize aggressive or submissive types of social behaviour, and unspecific changes which ar e similar in winners and losers and are likely to be induced by social stress.