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Updated: Jul 6, 2026
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
Analysis of ethanol reinforcement in 1-day-old rats: assessment through a brief and novel operant procedure
Kelly A Bordner1, Juan Carlos Molina, Norman E Spear
1Center for Developmental Psychobiology, Department of Psychology, Binghamton University-SUNY, Binghamton, New York 13902-600, USA.
Insights
Newborn rats readily self-administer ethanol using a novel operant technique, demonstrating an early affinity for the drug. This study validates findings of heightened ethanol reinforcement in early development.
Area of Science:
- Neuroscience
- Developmental Psychology
- Pharmacology
Background:
- Evidence suggests neonatal rats have a high affinity for ethanol and are sensitive to its reinforcing effects.
- Studying this early developmental period is challenging due to limited time and behavioral repertoires.
- A novel operant technique was developed to assess neonatal ethanol self-administration.
Purpose of the Study:
- To examine the predisposition of neonatal rats to self-administer ethanol and other reinforcers.
- To validate a new operant method for studying early-life ethanol consumption.
- To investigate the reinforcing effects of various ethanol concentrations in 1-day-old rats.
Main Methods:
- A novel operant technique was used with 1-day-old rats in a supine position.
- Intraoral infusions of milk, water, and ethanol (0.75-10%) were delivered based on sensor contact.
- Yoked controls received infusions independent of their own behavior to control for non-contingent exposure.
Main Results:
- Neonatal rats rapidly learned to operate for milk and low ethanol concentrations (0.75-10%).
- High responding was observed during extinction sessions after initial training with milk or 3% ethanol.
- Pharmacokinetic studies confirmed detectable blood ethanol levels correlating with concentration, achieved rapidly.
Conclusions:
- The developed operant technique is effective for studying early-life ethanol self-administration and seeking behaviors.
- Neonatal rats quickly learn to self-administer ethanol when paired with suckling-related behaviors.
- Results confirm a significant affinity for ethanol in early development, not attributable to general psychomotor effects.
Background:
An accumulating body of experimental evidence supports the notion that, early in development, heterogeneous rats exhibit heightened affinity for ethanol ingestion and are sensitive to the drug's postabsorptive reinforcing effects. The brevity of this ontogenetic period and the limited behavioral repertoire of the newborn represent obstacles in the examination of these phenomena. In the present study, we developed a novel operant technique aimed at examining the neonatal predisposition to gain access to intraoral infusions of different ethanol solutions and other potential reinforcers.
Methods:
In all experiments, 1-day-old rats were placed in a supine position that allowed access to a touch-sensitive sensor. In Paired pups, reinforcers were delivered through an intraoral cannula in a fixed-ratio-1 schedule, based on their physical contact with the sensor. Yoked controls were included to account for overall magnitude of behavioral responding and were given infusions in accord with behavior of the corresponding Paired pup. The reinforcement effect of milk, water and different ethanol solutions (0.75 to 10% v/v) was assessed using a single 15-minute conditioning session. Additional pharmacokinetic studies were conducted to determine blood ethanol concentrations attained during the course of the training session.
Results:
Within-subjects analysis revealed that Paired pups rapidly learned to increase the probability of behavioral execution to gain access to a biological reinforcer such as milk (Experiment 1). Follow-up experiments indicated that relatively low ethanol concentrations are equally likely to support operant performance (Experiments 2a and 3a). It was also observed that Paired pups exhibited surprisingly high levels of responding during an extinction session, particularly when initially trained with milk or 3% v/v ethanol as reinforcers (Experiment 4). The pharmacokinetic studies indicated that, within a short period of time, ethanol was detectable in blood. Levels attained during conditioning varied as a function of the ethanol concentration utilized as a reinforcer (Experiments 2b and 3b).
Conclusions:
The present technique appears to represent a valuable tool for examining ethanol self-administration and seeking behavior of the drug during early ontogeny. The results indicate that newborn rats, subjected to the explicit contingency comprising suckling-related behaviors and intraoral ethanol delivery (Paired pups), rapidly learn to gain access to the drug. These results are not explainable through psychomotor effects of ethanol as Yoked pups consumed similar amounts of ethanol and yet exhibited relatively low and consistent levels of responding. The overall pattern of results extends and validates previous observations of substantial affinity for ethanol during early stages of development, a phenomenon rarely encountered in genetically heterogeneous adult rats.
