Sex differences in long-term gonadectomized rats: monoamine levels and [3H]nitroimipramine binding in brain nuclei.

The levels of norepinephrine, dopamine, serotonin and the serotonin metabolite 5-hydroxyindoleacetic acid were measured in microdissected brain nuclei from long-term gonadectomized male and female rats. Females had 50 and 120% higher levels of serotonin in the anterior hypothalamic nucleus (AH) and arcuate-median eminence (AR-ME), respectively. No significant differences in norepinephrine, dopamine or 5-hydroxyindoline acetic acid were found in any of the brain nuclei sampled. The differences in serotonin content do not appear to result from a sexually dimorphic distribution of serotonin nerve terminals since quantitative autoradiography of 3H-nitroimipramine revealed no differences in binding between the sexes in the AH or AR-ME.