Astroglial Plasticity Is Implicated in Hippocampal Remodelling in Adult Rats Exposed to Antenatal Dexamethasone.

Vishvesh H Shende,Glenda E Gillies,Jolanta Opacka-Juffry,Simon Mcarthur

doi:10.1155/2015/694347

Abstract

The long-term effects of antenatal dexamethasone treatment on brain remodelling in 3-month-old male Sprague Dawley rats whose mothers had been treated with dexamethasone were investigated in the present study. Dorsal hippocampus, basolateral amygdala and nucleus accumbens volume, cell numbers, and GFAP-immunoreactive astroglial cell morphology were analysed using stereology. Total brain volume as assessed by micro-CT was not affected by the treatment. The relative volume of the dorsal hippocampus (% of total brain volume) showed a moderate, by 8%, but significant reduction in dexamethasone-treated versus control animals. Dexamethasone had no effect on the total and GFAP-positive cell numbers in the hippocampal subregions, basolateral amygdala, and nucleus accumbens. Morphological analysis indicated that numbers of astroglial primary processes were not affected in any of the hippocampal subregions analysed but significant reductions in the total primary process length were observed in CA1 by 32%, CA3 by 50%, and DG by 25%. Mean primary process length values were also significantly decreased in CA1 by 25%, CA3 by 45%, and DG by 25%. No significant astroglial morphological changes were found in basolateral amygdala and nucleus accumbens. We propose that the dexamethasone-dependent impoverishment of hippocampal astroglial morphology is the case of maladaptive glial plasticity induced prenatally.

Highlights

Astroglia have been acknowledged to play a role in brain responses to stress and glucocorticoids as its chemical mediators [1, 2]
A fixed counting frame of 50 × 50 and a variable sampling grid size (x-y-axis) of 150 × 150 CA1, 150 × 150 CA2, 300 × 300 CA3, and 300 × 300 DG were used for the dorsal hippocampus (Figure 1(b)) and 150 × 150 was used for both basolateral amygdala and nucleus accumbens
The present study was focused on the effects of antenatal glucocorticoid treatment (AGT) on central astroglia and regional volume of the hippocampus, amygdala, and nucleus accumbens as the areas of the limbic system implicated in response to stress and corticosteroids [2, 3, 9]

Summary

Introduction

Astroglia have been acknowledged to play a role in brain responses to stress and glucocorticoids as its chemical mediators [1, 2]. Such effects implicate brain plasticity and can lead to regional brain remodelling, with volume changes observed within the limbic system in cases of long-term “toxic” stress, and depression and depression-like conditions in humans and animals, respectively [1, 3]. Antenatal treatment with synthetic steroids such as dexamethasone, which cross the placenta [11], is often used in pregnant women at risk for preterm birth [12]. The present study addressed this gap in knowledge and hypothesised that rat hippocampal astroglia respond to AGT in a maladaptive manner, in the long term

Experimental Procedures

Stereological Procedures

Results

Discussion