Chronic corticosterone affects brain weight, and mitochondrial, but not glial volume fraction in hippocampal area CA3
Section snippets
Subjects
Ten male Sprague–Dawley rats (380–450 g) were habituated to the colony for 6 days and handled for an additional 5 days before treatment conditions commenced. Food and water were provided ad libitum, but monitored for the duration of the experiment. All treatment and testing protocols were approved by the institution's animal care and use committee and conformed to National Institutes of Health guidelines. All effort was made to minimize the number of animals used. Animals were well-handled
Body and organ weights
Despite the equal average body weight across groups at the beginning of treatment, the CORT group weighed less at the end of the experiment. A repeated measures ANOVA on mean body weights (with treatment as the between subjects factor and week as the within subjects factor) revealed a main effect for both treatment [F(1,8)=16.5, P<0.01; see Fig. 3] and week [F(8,64)=37.2, P<0.0001; see Fig. 3]. A significant interaction between treatment and week was also found [F(8,64)=15.9, P<0.0001; see Fig.
Discussion
Our findings indicate that elevating CORT for 56 days does not influence CA3 cell number or cell layer volume. These findings are consistent with previous studies utilizing unbiased counting methods (Vollmann-Honsdorf et al., 1997, Sousa et al., 1998, Leverenz et al., 1999). The dose used in the present study caused no reduction in the volume of the dorsal CA3 apical dendritic neuropil. Whereas we expected to see an increase in glial volume fraction, we did not find that in this study. Either
Conclusion
CORT elevations that were sufficient to reduce organ and muscle weight as well as significantly reduce brain weight, caused no gross anatomical alterations in the middle and proximal regions of dorsal CA3. Although CORT has been shown to reduce GFAP, glial volume fraction was not significantly reduced after exposure to elevated CORT for 56 days. In contrast, CORT reduced mitochondrial volume fraction, suggesting that metabolic capacity may be impaired. Because indications of damage were
Acknowledgements
We would like to thank Joe Fenstermacher for the generous use of his ultramicrotome. We would like to thank Rachel Encarnacion, Noriko Kawashima, Rabia Razi, Baynazier Ansari and Diana Lawrence for help handling animals, monitoring food and water, and collecting data. Glenn Hudson, Ralph Molaro and Robert Chorley have generously given their time to develop and maintain equipment used for this project.
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