Neocortical and Hippocampal Glial Fibrillary Acidic Protein Immunoreactivity Shows Region-Specific Variation during the Mouse Estrous Cycle

Abstract

Ovarian hormones modulate both neuronal and glial activation during the estrous cycle. These effects are particularly well characterized in the hypothalamus. Ovarian hormones also affect brain regions not directly related to reproductive function. In this study we used glial fibrillary acidic protein (GFAP) immunocytochemistry to quantify astroglial cells and process density in both the neocortex and hippocampus during the estrous cycle. Our data show that the density of GFAP immunoreactive processes in the hippocampus peaks on proestrus although cell density does not change. In contrast, both GFAP immunoreactive cell and process densities are elevated on diestrus and proestrus in the supragranular layer of the somatosensory cortex and reach a nadir on estrus and metestrus. This activation pattern is not apparent in the motor or cingulate cortex. Neocortical GFAP immunoreactivity appears to follow the distribution of estrogen receptor-α-like immunoreactivity. Our data show that ovarian hormones have regionally specific effects on glial activation within the neocortex. Characterizing glial activation by ovarian hormones is important since astroglia are the source of numerous trophic factors and play an important, although often unrecognized, role in neuronal metabolism and function.

Age-related decreases in SYN levels associated with increases in MAP-2, apoE, and GFAP levels in the rhesus macaque prefrontal cortex and hippocampus

“…Here, we report an increase in GFAP immunoreactivity, without an increase in the number of cells expressing GFAP. Thus, the apparent increase in GFAP immunoreactivity observed in this study is most likely due to the increase in cell size and number of processes expressing GFAP, corroborating rodent studies (Landfield et al 1977;Lindsey et al 1979;GarciaSegura et al, 1994a, b;Garcia-Segura et al 1994a, b;Berciano et al 1995;Garcia-Segura et al 1996;Struble et al 2006). Moreover, other nonhuman primate studies demonstrate that the cytoarchitecture of glial cells change with age but not the number of glial cells (Peters and Sethares 2002;Sandell and Peters 2002).…”

Short- and long-term treatment with estradiol or progesterone modifies the expression of GFAP, MAP2 and Tau in prefrontal cortex and hippocampus

“…Furthermore, it has been observed that GFAP synthesis is accompanied by the growth of glial processes that displace the synaptic terminals (Dhandapani et al, 2003). This estrogenic up-regulation of GFAP expression in hippocampus coincides with two reports showing that GFAP expression in hippocampus peaks on proestrus, implying high levels of E2 (Struble et al, 2006;Arias et al, 2009).…”

“…This protein, among other functions, provides motility and stability to astrocytes, which play a role in synaptic plasticity (Gómora-Arrati et al, 2010). It has been reported that E2 increases the expression of GFAP in hippocampus and several other areas related with reproductive functions (Day et al, 1993;Struble et al, 2006;Garcia-Segura et al, 1994;Kohama et al, 1995). Furthermore, it has been observed that GFAP synthesis is accompanied by the growth of glial processes that displace the synaptic terminals (Dhandapani et al, 2003).…”

Long-term effects of estradiol replacement in the olfactory system

“…GFAP process density was calculated by a point count method of grid intersections (Struble, et al, 2006). A 5 X 5 cell grid, 25 μm/cell side, was overlaid on the live image and each immunostained process (but not cell body) intersecting the grid was marked (Fig.…”