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A Method for Evaluating the Reinforcing Properties of Ethanol in Rats without Water Deprivation, Saccharin Fading or Extended Access Training
Published on: January 29, 2017
Motivational effects of intraorally-infused ethanol in rat pups in an operant self-administration task
Ricardo M Pautassi1, Eric Truxell, Juan C Molina
1Center for Developmental Psychobiology, Binghamton University, Binghamton, NY 13902-6000, USA. pautassi@binghamton.edu
Insights
Infant rats found self-administered ethanol aversive, performing fewer responses. This suggests early ethanol exposure may have negative hedonic effects in young rodents.
Area of Science:
- Neuroscience
- Developmental Psychology
- Pharmacology
Background:
- Self-administration of ethanol is a key model for studying addiction.
- Limited research exists on ethanol's motivational effects in preweaning animals due to task limitations.
Purpose of the Study:
- To assess the hedonic impact of intraoral ethanol self-administration in infant rats.
- To establish an age-appropriate operant task for studying early ethanol exposure.
Main Methods:
- Infant rats (postnatal days 14-16) self-administered intraoral ethanol (3% or 5%) via touch sensor activation.
- Paired animals controlled infusions, while yoked controls received equated infusions without behavioral control.
- Pre-exposure to ethanol's sensory/pharmacological effects occurred on postnatal day 13.
Main Results:
- Rats receiving ethanol infusions controlled by their behavior performed fewer responses than controls.
- Operant response rates decreased across sessions in the paired group.
- These findings indicate an aversive hedonic value of ethanol in this age group.
Conclusions:
- Intraoral ethanol self-administration is perceived as aversive by two-week-old rats.
- The orosensory properties of ethanol appear to contribute to its negative hedonic impact in early development.
- This study provides a novel method for assessing early ethanol's effects.
Abstract:
Motivational effects of self-administered ethanol have rarely been studied in preweanling rats due primarily to the lack of age-appropriate operant tasks. The present experiments assessed the hedonic effects of intraoral ethanol in infant rats self-administered by activating a touch sensor. On postnatal day (PD) 13 pups were pre-exposed to the drug's pharmacological and/or sensory effects. Operant sessions were conducted during PDs 14-16 (Experiments 1 and 2). Paired animals were placed in chambers equipped with a touch-sensitive disk and received an intraoral infusion of ethanol (3 or 5% v/v, 5 microl) after each sensor contact. Yoked controls were equated for number and distribution of ethanol infusions but had no control over the contingency between operant behavior and intraoral infusion. In Experiment 2, training trials were preceded by a non-reinforced phase. Paired pups performed fewer operant responses than controls and decreased their operant responses across sessions. These results suggest that intraoral self-administered ethanol has an aversive hedonic value in two-week old rats. Operant behavior seems to have been associated with aversive orosensory effects derived from intraoral ethanol infusion.
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