Relative responding on concurrent schedules: indexing ethanol's reinforcing efficacy

Area of Science:

• Behavioral pharmacology
• Neuroscience
• Animal models of addiction

Background:

• Concurrent schedules of reinforcement are used to study choice behavior.
• Ethanol's reinforcing effects are a key factor in alcohol use disorders.

Purpose of the Study:

• To evaluate the utility of relative responding on a concurrent schedule as an index of ethanol's reinforcing efficacy.
• To investigate the influence of body weight changes on ethanol and water self-administration.

Main Methods:

• Rats were trained on a concurrent schedule of fixed ratio 8 (FR8) for ethanol (5% v/v) or water access.
• Body weight was manipulated from 80% to 110% of ad libitum intake.
• Response proportions and absolute responding were recorded.

Main Results:

• Stable concurrent fixed ratio (FR8 FR8) responding for ethanol and water was established.
• The proportion of responses for ethanol ranged from 77% to 98% across rats and remained stable.
• Both absolute and proportional ethanol responding decreased with increased body weight, with absolute responding showing a greater change.

Conclusions:

• Relative responding on concurrent schedules provides a stable index of ethanol's reinforcing efficacy.
• Interpreting drug availability context is crucial when using relative responding measures.
• Body weight influences ethanol self-administration, affecting both absolute and relative responding.