[Sex difference of rat brain monoamine metabolism under restraint stress].

Sex-dependent changes in dopamine (DA) and serotonin (5HT) metabolisms under restraint stress were investigated in correlation with sex hormones. Male and female rats were divided into normal (in which female rats were further divided into proestrus, estrus, metestrus and diestrus subgroups), castrated, estradiol-given, progesterone-given, and testosterone-given groups. Each group were loaded with the same restraint stress, and DA, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5HT and 5-hydroxyindoleacetic acid (5HIAA) in the cerebral cortex, thalamus and brainstem were measured by the HPLC-ECD method. In the normal female group, all DA, 5HT and their metabolites showed remarkable increase under the stress during proestrus and estrus phases. These phenomenon were not found for the castrated female group, suggesting that estradiol and progesterone are related to stress reactions of DA and 5HT metabolisms. In male rats, however, no distinct difference in the stress reactions of monoamine metabolisms was noted between the normal and castrated groups. In comparison of the hormone-given groups with the castrated groups, the increase in DA and DOPAC in the brainstem for both sex and the increase in 5HIAA in the brainstem for females, were notable; in the progesterone-given group, DOPAC, HVA and 5HIAA were increased in female cerebral cortex, but not in male cortex. DA metabolism showed no great difference between the testosterone-given and the castrated groups for both sexes, but 5HIAA was increased in female cerebral cortex and brainstem. The above data show that stress reactions of DA and 5HT metabolisms in the brain differ according to sex, and suggest that estradiol and progesterone accelerate the stress reactions of DA and 5HT metabolisms.