Sex differences in distribution and identity of aromatase gene expressing cells in the young adult rat brain.

It is known that there are differences in the way males and females are mentally affected. These have been in part attributed to the effect of sex hormones, such as estrogen and testosterone. Within the framework of sex-specific medicine, it is therefore important to understand the biological substrates of sex-specific systems in the brain that are involved in any of these differences. The present study investigated the enzyme responsible for the synthesis of estrogen in the brain, to identify where it is expressed in the brain and to characterize the cells in which it is expressed. To this end, female and male young adult rats were studied. Brain slices including regions of relevance to, among others, emotion processing, were analyzed using fluorescent probes for the genes of interest and visualized using microscopy. Automated cell counting illustrated sex differences, with males displaying greater expression of the aromatase gene, compared with females, in several regions. The aromatase gene was expressed together with genes for the major inhibitory and excitatory neurotransmitters.