Impact of Adolescent Intermittent Ethanol Exposure on Social Investigation, Social Preference, and Neuronal Activation in cFos-LacZ Male and Female Rats

Abstract

Adolescence is a sensitive developmental period during which alcohol use is often initiated and consumed in high quantities, often at binge or even high-intensity drinking levels. Our lab has repeatedly found that adolescent intermittent ethanol (AIE) exposure in rats results in long-lasting social impairments, specifically in males, however our knowledge of the neuronal underpinnings to this sex-specific effect of AIE is limited. The present study was designed to test whether social anxiety-like alterations in AIE-exposed males would be accompanied by alterations of neuronal activation across brain regions associated with social behavior, with AIE females demonstrating no social impairments and alterations in neuronal activation. Adolescent male and female cFos-LacZ transgenic rats on a Sprague-Dawley background were exposed to ethanol (4 g/kg, 25% v/v) or water via intragastric gavage every other day during postnatal days (P) 25–45 for a total of 11 exposures (n = 13 per group). Social behavior of adult rats was assessed on P70 using a modified social interaction test, and neuronal activation in brain regions implicated in social responding was assessed via β-galactosidase (β-gal) expression. We found that AIE exposure in males resulted in a significantly lower social preference coefficient relative to water-exposed controls, with no effect evident in females. Exposure-specific relationships between social behavior and neuronal activation were identified, with AIE eliminating correlations found in water controls related to social interaction, and eliciting negative correlations mainly in limbic regions in a sex-specific manner. AIE exposure in the absence of social testing was also found to differentially affect neural activity in the orbitofrontal cortex and central amygdala in males and females. These data suggest that AIE produces sex-specific social impairments that are potentially driven by differential neuronal activation states in regions important for social behavior, including the medial prefrontal and orbitofrontal cortices, nucleus accumbens, lateral septum, and central amygdala. Future studies should be focused on identification of specific neuronal phenotypes activated by interaction with a social partner in AIE-exposed subjects and their control counterparts.

Determining the neuronal ensembles underlying sex-specific social impairments following adolescent intermittent ethanol exposure

“…It has previously been shown that AIE exposure reduces activity-regulated cytoskeletal (Arc) gene expression Pandey 2015), decreases brain derived neurotrophic factor (BDNF) (Pandey 2015), and lowers neuropeptide Y protein (Kokare 2017) in the CeA, with these alterations associated with various behavioral impairments such as anxietylike behavior (Kokare et al, 2017;Kyzar et al, 2019;Kyzar et al, 2017;Pandey et al, 2015). In our previous study, reduced neuronal activation of the CeA was evident in AIE-exposed males, whereas females displayed a moderate increase in CeA neuronal activation (Towner et al, 2022a). These contradicting findings clearly show that more work is needed to understand the long-term consequences of AIE on CeA neuronal activation between sexes.…”

“…Prior work from our lab has found that AIE consistently results in sex-specific social deficits evident in adulthood (Dannenhoffer et al, 2018; Towner et al, 2022a; Varlinskaya et al, 2020; Varlinskaya et al, 2017; Varlinskaya et al, 2014). Specifically, males exposed to ethanol during adolescence show decreased social preference and social investigation, with these findings absent in females.…”

“…Social behavior was assessed using the modified social interaction test in accordance with our previous studies (Dannenhoffer et al, 2018; Towner et al, 2022a; Varlinskaya et al, 2020), Upon reaching adulthood (∼P70), LacZ+ rats were weighed, marked for identification, and placed into a testing apparatus (46.0 x 30.3 x 30.5 cm) that consisted of two equally sized chambers separated by an aperture, allowing for movement between compartments. Each apparatus contained pine shavings at the bottom and were cleaned with 6% hydrogen peroxide between sessions.…”

“…Given our prior findings of the PrL neuronal activation state positively correlating with social investigation in control males (Towner et al, 2022a), our primary hypothesis was that AIE-exposed males would have lower neuronal activation than water-exposed control males following exposure to a social stimulus. We expected sex-specific effects of AIE, with females displaying no difference in neuronal activation of the PrL between water-and AIE-exposed groups.…”

“…We recently utilized cFos-LacZ transgenic rats that co-expressed beta-galactosidase (β-gal and cFos for assessment of neuronal activation of brain regions within the social brain network in animals previously exposed to AIE (Towner et al, 2022a). We found that water-exposed control males had positive relationships between social investigation and neuronal activation of the mPFC, consisting of the prelimbic (PrL) and infralimbic (IL) cortices.…”