Sex and laterality differences in medial amygdala neurons and astrocytes of adult mice

Abstract

The posterodorsal aspect of the medial amygdala (MePD) in rats is sexually dimorphic, being larger and containing more and larger neurons in males than in females. It is also highly lateralized, with the right MePD larger than the left in both sexes, but with the smaller left MePD actually containing more and larger neurons than the larger right. Astrocytes are also strikingly sexually differentiated, with male-biased numbers and lateralized favoring the right in the rat MePD. However, comparable information is scant for mice where genetic tools offer greater experimental power. Hence, we examined the MePD from adult male and female C57Bl/6J mice. We now report that the MePD is larger in males than in females, with the MePD in males containing more astrocytes and neurons than in females. However, we did not find sex differences in astrocyte complexity or overall glial number nor effects of laterality in either measure. While the mouse MePD is generally less lateralized than in rats, we did find that the sex difference in astrocyte number is only on the right because of a significant lateralization in females, with significantly fewer astrocytes on the right than the left but only in females. A sex difference in neuronal soma size favoring males was also evident, but only on the left. Sex differences in the number of neurons and astrocytes common to both rodent species may represent core morphological features that critically underlie the expression of sex-specific behaviors that depend on the MePD.

Anti‐aging drugs reduce hypothalamic inflammation in a sex‐specific manner

“…This observation suggests the possibility of a threshold effect, the idea that inflammation in females may already be at such a low level that drug treatment cannot lead to further diminution. There is substantial evidence for sex‐specific differences in both microglia and astrocytes in the mouse brain (McCarthy & Arnold, ; Pfau et al ., ). Males have more microglia in the CA1, CA3, and dentate gyrus (DG) of the hippocampus and the amygdala early in postnatal development, whereas females have more microglia with an activated morphology later in development, that is, as juveniles and as young 3‐month‐old adults (Schwarz et al ., ).…”

Dissociable contributions of the amygdala to the immediate and delayed effects of emotional arousal on memory

“…Alternatively, the right amygdala was claimed to be part of a rapid emotional stimulus detection system, which would be consistent with a role in affect-based attention, whereas the left amygdala might be specialized for more sustained responses (Phillips et al 2001;Wright et al 2001;Sergerie et al 2008;Kohno et al 2015). In line with a functionaland/or sex-dependent lateralization of amygdala activity, rodents show an anatomical lateralization of the amygdala which is in part sex-dependent (Johnson et al 2008(Johnson et al , 2012Pfau et al 2016).…”

Gonadal hormones differentially regulate sex‐specific stress effects on glia in the medial prefrontal cortex

“…Although sparsely investigated, experiemental findings indicate sex differences in astrocyte density and morphology across a number of stress‐sensitive brain regions. For example, males show heightened astrocyte density and complexity in medial amygdala, whereas astrocytic complexity in hippocampus is greater in females . Astrocytes express ARs and ERs, alongside factors critical in steroidogenesis and steroid aromatisation .…”