[The effect of the repeated experience of victories and defeats in social conflicts on the function of the brain serotoninergic system in male mice].

Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels, tryptophan hydroxylase (TPH) activity, and 5-HT1A receptor binding were studied in brain areas of male mice after repeated experience of victories (winners) and defeats (losers) in daily male confrontations. A decrease in the TPH activity in midbrain and its decrease in hypothalamus were shown in winners in comparison with controls. The victory experiences were accompanied by a pronounced increase of Bmax of 5-HT1A receptors in the frontal cortex and decrease of Kd in the hypothalamus. Repeated defeats in social confrontations were accompanied by an increase in 5-HT level in the amygdala and increase of 5-HIAA/5-HT index in the hippocampus in comparison with controls. A decrease of Bmax in the hypothalamus and of Kd of 5-HT1A receptors both in the frontal cortex and hypothalamus was shown in losers as compared to controls. An increase in TPH activity under the influence of repeated defeats was shown in striatum and hypothalamus. The obtained evidence point to specific changes in serotonergic activity which characterize aggressive or submissive types of social behaviour, and unspecific changes which are similar in winners and losers and are likely to be induced by social stress.