Comparative analysis of anxiety-like behavior in partition and plus-maze tests after agonistic interactions in mice.

The behavior of C57BL/6J male mice with experience of repeated victories (winners) or defeats (losers) in daily agonistic interactions, was examined in the plus-maze and partition tests. The latter procedure assesses the reactivity of mice to another conspecific in the neighboring compartment of a common cage, communicative behavior or level of sociability. The behavior of mice after 10 days (T10) and 20 days (T20) of agonistic confrontations, as well as in controls (5 days of individual housing) was analyzed. Significant differences were found between T10 and T20 losers and controls in both tests. In the partition test, a decrease in the number of approaches and total and average time spent near the partition was found in T10 and, more pronounced, in T20 losers. In the plus-maze, losers showed fewer open and total entries than controls. Moreover, rarely did they pass from one enclosed arm to another, and also showed a decreased number of 'peepings' from enclosed arms. Percentage of open time did not differ significantly in losers compared to controls. It is suggested that the level of losers' sociability, estimated as low by the partition test, can include anxiety as a component, which is confirmed, at least partly, by some parameters of the plus-maze test. There were no differences in the partition or plus-maze tests between T10 winners and controls. However, all parameters of partition behavior were significantly different between T20 winners and controls. In the plus-maze, similar to losers, T20 winners displayed fewer open arm entries, number of "peepings,' and passages than controls. It was concluded that parameters of the partition and plus-maze tests correlate in mice with the alternative experience of agonistic confrontations, positive or negative. A combination of these two tests may be used for estimation of developing anxiety in mice.

[The effect of the repeated experience of victories and defeats in social conflicts on the function of the brain serotoninergic system in male mice]. / Vliianie povtornogo opyta pobed i porazhenii v sotsial'nykh konfliktakh na sostoianie serotoninergicheskoi sistemy golovnogo mozga samtsov myshei.

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.