Günther Gehlen

Glial fibrillary acidic protein immunodetection and immunoreactivity in the anterior and posterior medial amygdala of male and female rats

The medial amygdala (MeA) has receptors for gonadal hormones and modulates reproductive behaviors in rats. Adult male and female rats were used for the immunodetection, a less accurate technique, and the immunohistochemistry for the astrocytic marker glial fibrillary acidic protein (GFAP) in the anterior and posterior MeA. Both procedures were done using polyclonal anti-GFAP and were quantified by densitometry. The first technique provided no evidence for a difference between sexes in the immunocontent of GFAP in any region of the MeA (p > 0.1). Nevertheless, the measure of the intensity of GFAP immunoreactivity (GFAP-IR) showed that females had a higher GFAP-IR in the posterodorsal (p < 0.01) and in the posteroventral subregions of the MeA (p < 0.01) than males. No sex difference was found in its anterodorsal part (p > 0.1). The present results point out the differences between these two above-mentioned techniques but add a new finding to the previously described sexual dimorphism in the MeA, i.e., the GFAP-IR. Data also suggest that probably astrocytes can be affected by sex steroids in this brain area. It is likely that this regionally specific difference in the GFAP-IR may contribute to the distinct functional roles that the MeA subregions have in male and female rats.

Dendritic branching features of posterodorsal medial amygdala neurons of adult male and female rats: Further data based on the Golgi method

The posterodorsal portion of the medial amygdalar nucleus (MePD) contains receptors for gonadal hormones and modulates the function of a social behavior network in rodents. The aims of this study were: to provide further data about the morphology of Golgi-impregnated dendrites of neurons from the MePD of adult rats; and, to compare the results obtained for dendritic branching and predominant dendritic spatial distribution in the MePD of males and diestrus females. MePD neurons were classified as bitufted or stellate, their spiny dendrites showed variable lengths, divided sparingly and decreased the number of branches with the distance from the soma. Dendritic arborization levels, number of branches in each level, distribution of the dendrites around the cell body and away from it, and the preferred spatial distribution of dendritic branches were studied according to different techniques and compared between sexes. Statistically significant differences were found in the predominant dendritic spatial distribution in the MePD, males with branches more oriented medially and dorsolaterally and females with more dorsally and ventromedially ones (p< or =0.05 in all cases). This result adds another clue to understand how information is processed and integrated in the MePD and within functionally dynamic sex steroids-responsive circuits relevant for reproduction in both sexes.