Effects of escalating versus fixed ethanol exposure on ∆FosB expression in the mesocorticolimbic pathway in adolescent and adult rats

ABSTRACT

Background: We have reported induction of ∆FosB in adolescent rats that drank less ethanol than adults yet exhibited a progressive increase in ethanol intake.Objective: To test the hypothesis that an escalating pattern of ethanol exposure is more effective to induce ∆FosB expression [at prelimbic cortex (PrL), nucleus accumbens core and shell, striatum, basolateral amygdala (BLA) and central amygdala (CeC)] than a pattern equated for number of exposures yet employing a fixed ethanol dose.Methods: Adolescent and adult (Exp. 1, n = 48) male and female (n = 24 of each sex) or only adult male (Exp. 2, n = 36) Wistar rats were intermittently intubated with vehicle, escalating (from 0.5 to 2.5 g/kg) or fixed (2.0 g/kg) doses of ethanol, across 18 sessions. ∆FosB induction was assessed using immunohistochemistry. Ethanol intake, anxiety and risk-taking were assessed (in adults only) via two-bottles tests and the multivariate concentric square field.Results: Both patterns heightened ∆FosB levels similarly in adolescents and adults and in males and females. Fixed dosing induced ∆FosB in all areas (p < .05) except the CeC, whereas the escalating pattern induced ∆FosB in the PrL and BLA only (p < .05). Ethanol intake was initially lower in ethanol pre-exposed subjects than in control subjects (p < .05). Rats exposed to the fixed pattern exhibited enhanced risk-taking behavior (p < .05).Conclusions: The results agree with studies showing ethanol-mediated induction of ∆FosB in reward areas and indicate that, following ethanol intubations, this induction is similar in adolescents and adults. The induction of ∆FosB seems not necessarily associated with susceptibility for ethanol intake.

KEYWORDS:

• Ethanol exposure
• adolescent rats
• adult rats
• ∆FosB
• intubations

Contributors

Ricardo Pautassi, Conceptualization, Visualization, Data curation, Writing – Original draft preparation, Funding acquisition. Aranza Wille-Bille: Conceptualization, Visualization, Data curation, Project administration, Investigation, Writing – original draft. Andrea Godino, Investigation, Project administration; Resources. Leonardo Marengo: Conceptualization, Visualization, Data curation, Project administration, Investigation, Writing – original draft.

Disclosure statement

All of the authors declare that they have no conflicts of interest.

Additional information

Funding

This work was supported by grants from the Agencia Nacional de Promoción Científica y Técnica [FONCYT 2015-0325] and Universidad Nacional de Córdoba (SECyT-UNC) to Ricardo Pautassi. This work was also supported by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina). The funding agencies had no role in the study design, collection, analysis, and interpretation of data, writing the manuscript, or decision to submit the paper.