Sensitivity and Resilience to Stress‐Induced Alcohol Intake Enhancement Produces Sex Differences in the Corticotropin Releasing Factor System in Male and Female C57BL/6J Mice

Abstract

Post‐traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are prevalent disorders with higher lifetime comorbidity among females. Stress has been shown to increase alcohol drinking, along with evidence confirming associations between PTSD and AUD. We developed a model of traumatic stress and PTSD using predator odor stress (PS) wherein repeated PS exposures significantly increased anxiety‐related behavior, corticosterone levels, and neuronal activation in the hippocampus (HIPP) and prefrontal cortex (PFC) in naïve C57BL/6J mice. Intermittent PS exposure (30 min dirty rat bedding) also significantly increased subsequent alcohol drinking in “sensitive” mice, with heterogeneity of responses as seen with comorbid PTSD and AUD. The purpose of our present study was to determine whether PS‐enhanced drinking in “sensitive” mice produced sex differences in several proteins important for CRF system function based on previous evidence regarding sex differences in the responsivity to stress and the CRF system. Drinking preference (10% ethanol vs water) was measured for 7 weeks in adult male and female mice (4 weeks baseline, 2 weeks with intermittent PS, 1 week post‐stress). Median and interquartile ranges were used to identify “sensitive” (> 20% increase in alcohol drinking over baseline) and “resilient” (no change or decrease in drinking from baseline) subgroups. In the “sensitive” subgroup, alcohol drinking was increased by 69% in males and by 46% in females, with heterogeneity in response (17.5% of males, 12.5% of females were “PS‐sensitive”). Brains were harvested 24 hrs from the final drinking session, PFC and HIPP were dissected and frozen for Western Blot analyses of CRF receptor 1 (CRF‐R1), CRF‐R2, CRF binding protein (CRF‐BP), and glucocorticoid receptor (GR) vs separate naïve age‐matched mice, quantifying protein levels for each subgroup. In female PFC, all 4 proteins were significantly increased (17–28%) in the “sensitive” subgroup vs naïve, and these differences were significantly higher than in the “resilient” subgroup. In contrast, there were no significant increases in protein levels in “sensitive” male PFC vs naïve, and a significant “sensitive” vs “resilient” subgroup difference in CRF‐R2 and CRF‐BP was due to lower protein levels in the “resilient” subgroup. In male and female HIPP, CRF‐R1 levels were significantly decreased by 20% and 25%, respectively, in the “resilient” subgroup vs naïve. CRF‐R1 and GR levels were significantly lower in the “resilient” vs “sensitive” female subgroup. In contrast, CRF‐BP levels were significantly lower in “resilient vs “sensitive” males, while both male and female “resilient” vs “sensitive” subgroups had significantly lower levels for CRF‐R2. Taken together, these results continue to support the suggestion that a history of ethanol drinking and stress interact to increase the risk for harm from subsequent drinking in “sensitive” mice, with important sex differences in drinking behaviors and brain protein changes relevant to CRF system function.Support or Funding InformationSupported by BX002966 (DF) from the Department of Veteran Affairs