Effects of early social isolation and adolescent single prolonged stress on anxiety-like behaviors and voluntary ethanol consumption in female Long Evans rats.

Background: Exposure to stress during childhood and adolescence is a risk factor for alcohol use disorder (AUD) and comorbid conditions, including posttraumatic stress disorder (PTSD). We previously established an adolescent social isolation (SI) model that leads to the emergence of a wide range of behavioral risk factors for AUD, including increased anxiety-like behavior, locomotor activity, and ethanol consumption in male and female rats. Here, we sought to test the hypothesis that SI may increase vulnerability to single prolonged stress (SPS), a rodent model of PTSD.

Methods: Female Long Evans rats (n = 8/group) were either single-housed or group-housed (GH) (4/cage) on postnatal day 21. One week later, rats underwent testing in the open field test (OFT), elevated plus-maze (EPM), and successive alleys test (SAT). Following initial behavioral testing, a subset of SI/GH rats were exposed to SPS. All rats were then tested on the novelty-suppressed feeding test (NSFT) followed by fear conditioning and home cage two-bottle choice to assess ethanol consumption.

Results: SI significantly increased activity in the OFT and anxiety-like behavior on the SAT, but not the EPM. While SI and SPS alone had no effect on the NSFT, exposure to both stressors significantly increased approach latency. Complex effects of stress history were observed across a 3-day fear conditioning paradigm and no group differences were observed with home cage ethanol consumption, regardless of prior ethanol exposure.

Conclusions: The results from this study provide novel evidence that SI interacts with SPS in female rats to influence behavior in assays of unconditioned anxiety-like behavior (NSFT) and conditioned fear. Surprisingly, stress exposure had no effect on home cage ethanol consumption. Ultimately, these models provide useful avenues to examine the interaction between stressful experiences, alcohol exposure, biological sex, and the neurobiological adaptations underlying potential risk factors for psychiatric conditions.