Astrocytes in the rat medial amygdala are responsive to adult androgens

Abstract

The posterodorsal medial amygdala (MePD) exhibits numerous sex differences including differences in volume and in the number and morphology of neurons and astroctyes. In adulthood, gonadal hormones, including both androgens and estrogens, have been shown to play a role in maintaining the masculine character of many of these sex differences, but whether adult gonadal hormones maintain the increased number and complexity of astrocytes in the male MePD was unknown. To answer this question we examined astrocytes in the MePD of male and female Long Evans rats that were gonadectomized as adults and treated for 30 days with either testosterone or a control treatment. At the end of treatment brains were collected and immunostained for glial fibrillary acidic protein. Stereological analysis revealed that adult androgen levels influenced the number and complexity of astrocytes in the MePD of both sexes, but the specific effects of androgens were different in males and females. However, sex differences in the number and complexity of adult astrocytes persisted even in the absence of gonadal hormones in adulthood, suggesting that androgens also act earlier in life to determine these adult sex differences. Using immunofluorescence and confocal microscopy, we found robust androgen receptor immunostaining in a subpopulation of MePD astrocytes, suggesting that testosterone may act directly on MePD astrocytes to influence their structure and function.

Androgen receptors in muscle fibers induce rapid loss of force but not mass: Implications for spinal bulbar muscular atrophy

“…We suspect that this elevated level of T in Tg mice is due to their reduced body weight by 5 days of T treatment, as we have obtained similar findings in rats that differ in body weight. 30 …”

Regulation of astroglia by gonadal steroid hormones under physiological and pathological conditions

“…In the adult brain testosterone regulates the expression of GFAP in the hippocampus (Day et al, 1993(Day et al, , 1990) and reduces the aging-induced increase in GFAP expression in the cerebellum (Day et al, 1998). Testosterone also regulates the number and morphological complexity of astrocytes in the posterodorsal medial amygdala of male and female rats (Johnson et al, 2012). Furthermore, testosterone increases the number of astrocytes in the hippocampus and the interpeduncular nucleus of male rats (Emamian et al, 2010;Hajos et al, 1999).…”

The organizing actions of adolescent gonadal steroid hormones on brain and behavioral development

“…Furthermore, males carrying the testicular feminization mutation (tfm) of the androgen receptor and females do not display MePD increases in astrocyte number and branching during adolescence. In contrast, wildtype males display normative increases in MePD astrocyte number and branching, indicating that normative androgen receptor function is necessary for the adolescent development of this sexual dimorphism (Johnson, Breedlove, & Jordan, 2013; Johnson, Schneider, DonCarlos, Breedlove, & Jordan, 2012). Thus, strong evidence suggests that adolescent changes in astrocyte number and branching in males contributes to the sexual dimorphism in MePD cell volume.…”