Male and female mice living in differently-sized groups

Summary The influence of crowding in different group sizes on the metabolism of serotonin (5-HT) in six different brain areas and on some peripheral data in male and female mice was investigated. In the cortex, the diencephalon and in the basal ganglia, the 5-HT turnover of male mice increases with group size. The females react differently (Figs. 2, 3, 4). The densityinduced changes in the 5-HT metabolism of the mesencephalon correlated individually with the locomotor reactivity of the animals in an open-field (Figs. 8, 9). The septal area is the only part of the brain in male and female mice in which the 5-HT turnover increase depends on group size (Fig. 5).We wish to thank the Deutsche Abbott GmbH which supplied us with pargyline.