Ethanol-induced conditioned taste aversion and associated neural activation in male rats: Impact of age and adolescent intermittent ethanol exposure

PLOS ONE RESEARCH ARTICLE Ethanol-induced conditioned taste aversion and associated neural activation in male rats: Impact of age and adolescent intermittent ethanol exposure Jonathan K. Gore-Langton ID1,2, Elena I. Varlinskaya1,2,3, David F. Werner1,2,3*, in part of the Neurobiology of Adolescent Drinking in Adulthood Consortium (NADIA)¶ a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Center for Development and Behavioral Neuroscience, Binghamton University, Binghamton, New York, United States of America, 2 Department of Psychology, Binghamton University, Binghamton, New York, United States of America, 3 Developmental Exposure Alcohol Research Center, Binghamton, New York, United States of America ¶ Information on Membership of the Neurobiology of Adolescent Drinking in Adulthood Consortium (NADIA) is provided in the Acknowledgments. * Abstract OPEN ACCESS Citation: Gore-Langton JK, Varlinskaya EI, Werner DF, in part of the Neurobiology of Adolescent Drinking in Adulthood Consortium (NADIA) (2022) Ethanol-induced conditioned taste aversion and associated neural activation in male rats: Impact of age and adolescent intermittent ethanol exposure. PLoS ONE 17(12): e0279507. https://doi.org/ 10.1371/journal.pone.0279507 Editor: Andrey E Ryabinin, Oregon Health and Science University, UNITED STATES Received: May 31, 2022 Accepted: December 8, 2022 Published: December 22, 2022 Copyright: © 2022 Gore-Langton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting information files. Funding: This work was funded by NIH AA017823 (DFW) and AA019972 (DFW and EIV). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Individuals that initiate alcohol use at younger ages and binge drink during adolescence are more susceptible to developing alcohol use disorder. Adolescents are relatively insensitive to the aversive effects of alcohol and tend to consume significantly more alcohol per occasion than adults, an effect that is conserved in rodent models. Adolescent typical insensitivity to the aversive effects of alcohol may promote greater alcohol intake by attenuating internal cues that curb its consumption. Attenuated sensitivity to the aversive effects of alcohol is also retained into adulthood following protracted abstinence from adolescent intermittent ethanol (AIE) exposure. Despite these effects, much remains unknown regarding the neural contributors. In the present study, we used a conditioned taste aversion (CTA) paradigm to investigate neuronal activation in late-developing forebrain structures of male adolescents and adult cFos-LacZ transgenic rats as well as in AIE adults following consumption of 0.9% sodium chloride previously paired with an intraperitoneal injection of 0, 1.5 or 2.5 g/kg of ethanol. Adults that were non-manipulated or received water exposure during adolescence showed CTA to both ethanol doses, whereas adolescents displayed CTA only to the 2.5 g/kg ethanol dose. Adults who experienced AIE did not show CTA. Adults displayed increased neuronal activation indexed via number of β-galactosidase positive (β-gal+) cells in the prefrontal and insular cortex that was absent in adolescents, whereas adolescents but not adults had a reduced number of β-gal+ cells in the central amygdala. Adults also displayed greater corticalinsular functional connectivity than adolescents as well as insular-amygdalar and prefrontal cortex-accumbens core functional connectivity. Like adolescents, adults previously exposed to AIE displayed reduced prefrontal-insular cortex and prefrontal-accumbal core functional connectivity. Taken together, these results suggest that attenuated sensitivity to the aversive effects of ethanol is related to a loss of an insular-prefrontal cortex-accumbens core circuit. PLOS ONE | https://doi.org/10.1371/journal.pone.0279507 December 22, 2022 1 / 21 PLOS ONE Competing interests: The authors have declared that no competing interests exist. Effects of age and adolescent intermittent ethanol exposure on CTA neural activity Introduction Alcohol is the most used drug among adolescents worldwide. According to the Monitoring the Future survey, in 2020 more than half (55.3%) of high school seniors had used alcohol in the past year and 16.8% drank at binge levels within the past two weeks [1]. Rates of past-year alcohol use and binge drinking, defined by the National Institute of Alcohol Abuse and Alcoholism as a pattern of drinking that brings blood alcohol concentrations to 0.08 g/dl or above, were lower for 10th graders (40.7 and 9.6%) and 8th graders (20.5 and 4.5%). Several studies have shown that early onset of alcohol use as well as an escalation of drinking during adolescence increases the risk of developing an alcohol use disorder (AUD) in adulthood [2–4]. According to the Substance Abuse and Mental Health Services Administration [5], adolescents and adults display different patterns of alcohol drinking: while adults consume alcohol more frequently than adolescents, adolescents tend to drink substantially more per occasion, with some adolescents demonstrating high-intensity or extreme binge drinking by consuming 10+ and even 15+drinks in a row [6, 7]. (It is unfortunate that alcohol use is relatively high among adolescents, given that this demographic is particularly susceptible to the long-term negative neurocognitive and neurodevelopmental effects of alcohol. For example, binge drinking during adolescence has been associated with impairment of attention, information retrieval, and visuospatial skills [8]. Magnetic resonance imaging (MRI) studies have shown that hippocampal volumes tend to be smaller in adolescents with AUDs than age-matched controls and that this effect is more pronounced with earlier alcohol onset and greater duration of drinking [9, 10]. Given the established harms of adolescent alcohol use, it is important to characterize neural contributors to adolescent-typical binge and high-intensity drinking and to investigate alcohol-induced alterations in the developmental trajectory of the adolescent brain. Therefore, animal models (typically rodents) are a useful tool for understanding adolescent-typical responsiveness to ethanol as well as the neural perturbations caused by adolescent ethanol exposure, which is often not possible with human subjects. Animal models allow for control of several variables, including genetic background, environmental conditions, and ethanol exposure regimens (dose, frequency, age, and duration of exposure), while manipulating only variables of interest (e.g., age, sex, early experience, etc). Animal studies recapitulate that adolescent rats (...truncated)