Corticosterone Levels and Glucocorticoid Receptor Gene Expression in High Drinking in the Dark Mice and Their Heterogeneous Stock (HS/NPT) Founder Line

Abstract

The High Drinking in the Dark (HDID-1) line of mice has been selectively bred for achieving high blood alcohol levels (BALs) in the Drinking in the Dark task, a model of binge-like drinking. Recently, we determined that glucocorticoid receptor (GR) antagonism with either mifepristone or CORT113176 (a selective GR antagonist) reduced binge-like ethanol intake in the HDID-1 mice, but not in their founder line, HS/NPT. Here, we examined whether the selection process may have altered glucocorticoid functioning by measuring (1) plasma corticosterone levels and (2) expression of the genes encoding GR (Nr3c1) and two of its chaperone proteins FKBP51 and FKBP52 (Fkbp5 and Fkbp4) in the brains (nucleus accumbens, NAc) of HDID-1 and HS/NPT mice. We observed no genotype differences in baseline circulating corticosterone levels. However, HDID-1 mice exhibited a greater stimulated peak corticosterone response to an IP injection (of either ethanol or saline) relative to their founder line. We further observed reduced basal expression of Fkbp4 and Nr3c1 in the NAc of HDID-1 mice relative to HS/NPT mice. Finally, HDID-1 mice exhibited reduced Fkbp5 expression in the NAc relative to HS/NPT mice following an injection of 2 g/kg ethanol. Together, these data suggest that selective breeding for high BALs may have altered stress signaling in the HDID-1 mice, which may contribute to the observed selective efficacy of GR antagonism in reducing binge-like ethanol intake in HDID-1, but not HS/NPT mice. These data have important implications for the role that stress signaling plays in the genetic risk for binge drinking.

Involvement of FKBP5, but not of stress, in alcohol memory reconsolidation

“…Interestingly, we also found that acute alcohol injection increased the mRNA brain expression of Fkbp5, in line with previous reports [32][33][34] . We further show that this effect did not depend on the alcohol-drinking history of the mice, nor did we find significant effects of long-term alcohol consumption on this gene's expression.…”

“…Within the nucleus, GR acts as a transcription factor, with FKBP5 itself being one of its transcriptional targets 27,30 . Indeed, activation of the HPA axis, triggered by stress 31 or by alcohol exposure [32][33][34] , increases brain FKBP5 expression.…”

Development and implementation of a Dependable, Simple, and Cost-effective (DSC), open-source running wheel in High Drinking in the Dark and Heterogeneous Stock/Northport mice

“…Moreover, recent work from Savarese et al found that female and male iHDID-1 mice have higher corticosterone responses to a mild stressor (i.p. injections of ethanol or saline) than HS/Npt mice and show reduced glucocorticoid receptor (GR) gene expression in the nucleus accumbens (NAc; critical role in reinforcing and motivated behaviors) both basally and following ethanol administration (2 g/kg) (Savarese et al, 2022 ). Future work using these mice would help identify potential neurobiological markers of stress-related signaling (i.e.…”

Targeting the Maladaptive Effects of Binge Drinking on Circadian Gene Expression

“…The selective glucocorticoid receptor (GR) antagonist CORT113176 was shown to reduce binge-like ethanol drinking in female and male HDID-1 mice, but not their heterogeneous founders, the HS/Npt [ 74 ]. Recent work by Savarese, Grigsby [ 75 ] found no major differences in basal corticosterone levels between HDID-1 and HS/Npt mice, levels were only compared at one timepoint (during the light cycle, when corticosterone levels are relatively low). It would be interesting to see whether differences in daily glucocorticoid oscillations between HDID-1 and HS/Npt mice exist and whether chronic drinking differentially impacts these rhythms.…”

“…RNA isolation and cDNA synthesis was performed according to a previously established method [ 75 ]. Following tissue collection of the NAc, SCN, and VTA, RNA was isolated in Purezol reagent and collected using the Bio-Rad Aurum Total RNA Fatty and Fibrous Tissue Kit.…”