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Operant responding controlled by milk or milk contaminated with alcohol as positive reinforcers in infant rats
H D Dominguez1, G Bocco, M G Chotro
1Instituto de Investigacion Medica Mercedes y Martin Ferreyra, Cordoba, Argentina.
Insights
Infant rats readily consumed milk and ethanol-contaminated milk, demonstrating alcohol
Area of Science:
- Neuroscience
- Developmental Psychology
- Behavioral Pharmacology
Background:
- Early life exposure to substances can impact development.
- Understanding the reinforcing properties of ethanol (EtOH) in infancy is crucial.
Purpose of the Study:
- To investigate the reinforcing effects of ethanol-contaminated milk in infant rats.
- To examine age-related differences in the consumption of ethanol during early development.
Main Methods:
- Operant conditioning procedures were used with infant rats (weeks 1-3).
- Rats were trained to press a lever for milk or milk with 6.0% ethanol.
- Forced intake experiments were also conducted for comparison.
Main Results:
- Infant rats showed increased responding for both milk and ethanol-laced milk compared to controls.
- Plain milk was a more effective reinforcer than ethanol-laced milk.
- Developmental differences were observed in the response to ethanol-laced milk.
Conclusions:
- Ethanol partially reduces the reinforcing effects of milk but remains a positive reinforcer in early life.
- Infant rats demonstrate the capacity to learn and respond for ethanol-containing substances.
- These findings highlight developmental changes in alcohol's effects during infancy.
Abstract:
Infant rats during the first, second, or third week of life were tested in operant conditioning with uncontaminated milk or milk supplemented with 6.0% v/v absolute ethanol (EtOH) as the reinforcer. Relative to yoked controls, pups of each age group reinforced on a response-contingent basis exhibited a significantly higher rate of responding with either reinforcer. In terms of amount of reinforcement, milk induced a higher rate of lever pressing than did the EtOH-contaminated compound. Age-related differences in the onset of differential responding for plain milk and EtOH-contaminated milk suggested developmental changes in the effects of alcohol. In a second experiment, forced drinking of milk and EtOH-contaminated milk was compared in similar age groups. Patterns of intake resembled the patterns of operant responding controlled by the same substance in the first experiment. These experiments indicate that the presence of alcohol in milk partially inhibits the reinforcing capacity of uncontaminated milk. Nevertheless, the former compound is still effective as a positive reinforcer during the first weeks of life.