Sex and context differences in the effects of trauma on comorbid alcohol use and post-traumatic stress phenotypes in actively drinking rats

Alcohol use disorder (AUD) and affective disorders are frequently comorbid and share underlying mechanisms that could be targets for comprehensive treatment. Post-traumatic stress disorder (PTSD) has high comorbidity with AUD, but comprehensive models of this overlap are nascent. We recently characterized a model of comorbid AUD and PTSD-like symptoms, wherein stressed rats receive an inhibitory avoidance (IA)-related footshock on two occasions followed by two-bottle choice (2BC) voluntary alcohol drinking. Stressed rats received the second footshock in a familiar (FAM, same IA box as the first footshock) or novel context (NOV, single-chambered apparatus); the FAM paradigm more effectively increased alcohol drinking in males and the NOV paradigm in females. During abstinence, stressed males displayed avoidance-like PTSD symptoms, and females showed hyperarousal-like PTSD symptoms. Rats in the model had altered spontaneous action potential-independent GABAergic transmission in the central amygdala (CeA), a brain region key in alcohol dependence and stress-related signaling. However, PTSD sufferers may have alcohol experience prior to their trauma. Here, we therefore modified our AUD/PTSD comorbidity model to provide 3 weeks of intermittent extended alcohol access before footshock and then studied the effects of NOV and FAM stress on drinking and PTSD phenotypes. NOV stress suppressed the escalation of alcohol intake and preference seen in male controls, but no stress effects were seen on drinking in females. Additionally, NOV males had decreased action potential-independent presynaptic GABA release and delayed postsynaptic GABA_A receptor kinetics in the CeA compared to control and FAM males. Despite these changes to alcohol intake and CeA GABA signaling, stressed rats showed broadly similar anxiogenic-like behaviors to our previous comorbid model, suggesting decoupling of the PTSD symptoms from the AUD vulnerability for some of these animals. The collective results show the importance of alcohol history and trauma context in vulnerability to comorbid AUD/PTSD-like symptoms.