Voluntary adolescent alcohol exposure does not robustly increase adulthood consumption of alcohol in multiple mouse and rat models

Abstract

Adolescence is a period of increased risk taking, including increased alcohol and drug use. Multiple clinical studies report a positive relationship between adolescent alcohol consumption and risk of developing an alcohol use disorder (AUD) in adulthood. However, few preclinical studies have attempted to tease apart the biological contributions of adolescent alcohol exposure, independent of other social, environmental, and stress factors, and studies that have been conducted show mixed results. Here we use several adolescent voluntary consumption of alcohol models, conducted across four labs in three institutes and with two rodent species, to investigate the ramifications of adolescent alcohol consumption on adulthood alcohol consumption in controlled, pre-clinical environments. We consistently demonstrate a lack of robust increases in adulthood alcohol consumption. This work highlights that risks seen in both human datasets and other murine drinking models may be due to unique social and environmental factors - some of which may be unique to humans.

Keywords: Adolescent alcohol; Alcohol use disorder; Behavior; Development; Ethanol; Rodent models.

Fig. 1.. Overall methods and models.

Experiments were conducted across three sites and four adolescent drinking paradigms. A-D, drinking in the dark model in mice, conducted at Penn State University; E-G, adolescent intermittent access model in mice, conducted at Binghamton University; H-K adolescent intermittent access model in rats, conducted at The Scripps Research Institute; and L-N adolescent chronic intermittent ethanol model in rats, conducted at Binghamton University. O, comparison of overall models. These four models cover a range of consumption paradigms and stress confounds such as paired or isolated housing. * = p < .05; ** = p < .01, *** = p < .001. PND: postnatal day; DID: drinking in the dark; IA2BC: intermittent access 2-bottle choice; CIE: chronic intermittent ethanol.

Fig. 2.. Sex and total adolescent alcohol consumption only modestly increase total alcohol consumption during adulthood DID in mice.

(A) Experimental timeline. (B) Neither sex nor adolescent DID exposure affect EtOH consumption on first adulthood 2 h exposure at PND 84. (C) Female mice drank more than male mice during the first 4 h binge session at PND 87, but this effect was not modulated by adolescent DID. (D) There were main effects of sex and adolescent DID on total EtOH consumption across all 16 days of adulthood DID. (E) Adolescent DID experience did not affect BECs achieved during the final adulthood binge session (n = 4 Adol H2O mice, n = 3 Adol DID mice, sexes combined). (F-H) Relationships between total adolescent EtOH consumption and each of the 3 adult binge drinking parameters – EtOH consumed in first 2 h exposure, first 4 h binge, and across all 16 sessions of DID. Significant predictors identified by GLME are indicated where appropriate. (I) Daily EtOH consumption during adulthood DID in female (top) and male (bottom) mice. (J) Adolescent DID did not affect body weight in female (top) or male (bottom) mice. (K) Female and male Adolescent DID mice do not change their drinking during the first 2 h exposure in adolescence (PND 28) compared to in adulthood (PND 84). (L) There was no difference in EtOH consumption during first binge day in adolescence (PND 31) compared to adulthood (PND 87). (M) While female mice do not show changes in total EtOH consumption in adolescence and adulthood DID, male mice show reduced total EtOH intake during adulthood DID. (N) Daily EtOH consumption in adolescent and adulthood DID in double drinking mice. Trendlines in F-H represent the line of best fit within each sex. Significant main effects are indicated as * = p < .05, ** = p < .01, **** = p < .0001.

Fig. 3.. Intake and preference for EtOH during a 2-bottle choice model after adolescent binge drinking in SST-Cre:Ai9 mice.

(A) Experimental timeline. (B-E) Mice which went through adolescent DID show increased preference and intake for 3 % EtOH on PND 84. (F-I) Female mice show a higher preference and intake of 7 % EtOH on PND 90. (J-M) Preference and intake of 10 % EtOH are highest in female mice which underwent adolescent DID. (N-Q) Sex influences both preference and intake of 10 % EtOH at PND 104. (R-T) Daily EtOH intake, preference, and total fluid consumption during adulthood 2-bottle choice. (U-V) Body weight is not affected by adolescent DID. Trendlines in d-E, h-I, l-M, P-Q indicate the lines of best fit for each sex. * = p < .05, ** = p < .01, *** = p < .001, **** = p < .0001.

Fig. 4.. Pair-housed C57Bl/6 J mice do not show changes in adulthood EtOH consumption in an IA2BC model.

(A) Experimental schematic. (B-E) Neither EtOH preference nor intake was altered as a function of sex or adolescent EtOH exposure during the first adulthood IA2BC session on PND 90. (F-I) Female mice consumed significantly more EtOH during the final adulthood IA2BC session on PND 120, but this was not modulated by adolescent EtOH exposure. (J-K) Female mice consumed more EtOH across all 15 adulthood drinking sessions. (L-M) EtOH intake and preference across all 15 IA2BC sessions, split by sex. Significant predictors identified by GLME are indicated on each graph. Trendlines in D-E, H-I, K represent the line of best fit for each sex. B-K: Each value represents one cage with two mice. ** = p < .01, *** = p < .001.

Fig. 5.. Group housed Wistar rats do not show increases in adulthood IA2BC following adolescent IA2BC.

(A) Experimental timeline. (B, C) Rats that underwent adolescent alcohol exposure do not show increased EtOH intake or preference during adulthood. (D) There is no significant effect of drinking session on EtOH intake following adolescent alcohol exposure. (E–I) Total adolescent EtOH consumption is not a significant predictor of total adulthood EtOH consumption, first adulthood EtOH exposure intake or preference, or last adulthood EtOH exposure intake or preference. Trendlines in E-I represent the line of best fit for each sex.

Fig. 6.. Adolescent CIE does not increase EtOH consumption during adulthood CIE in Fischer 344 rats.

(A) Experimental timeline. (B) EtOH intake declines throughout adolescent CIE. (C) Female and male rats show reduced EtOH intake during the first adulthood CIE session on PND 114 compared to the final adolescent CIE session on PND 74. (D) Female and male rats consume less total EtOH during adulthood CIE than in adolescent CIE. (E-G) Neither sex nor total adolescent EtOH intake were significant predictors of adulthood drinking measurements. Trendlines in E-G represent the line of best fit for each sex. * = p < .05; ** = p < .01; *** = p < .001. C-G: Each value represents EtOH intake in one cage of 2 rats.