Drug effects on fixed-interval responding with pause requirements for food presentation

Area of Science:

• Behavioral pharmacology
• Animal behavior

Background:

• Drug effects on behavior are often interpreted through rate-dependency.
• Response-spacing requirements can influence behavior under fixed-interval schedules.

Purpose of the Study:

• To investigate the influence of baseline response rates and response-spacing requirements on the behavioral effects of pentobarbital and d-amphetamine in pigeons.
• To determine if control response rate is a primary determinant of drug effects, independent of reinforcement density.

Main Methods:

• Pigeons were trained on a multiple schedule with fixed-interval components featuring different response-spacing requirements (tandem DRL for long pauses, tandem DRH for short pauses).
• The effects of pentobarbital (3, 10 mg/kg) and d-amphetamine (0.03 to 3 mg/kg) on overall and local key-pecking rates were analyzed.

Main Results:

• Pentobarbital increased low rates and decreased high rates, consistent with rate-dependency.
• D-amphetamine showed limited effects on low rates in tandem DRL components and its rate-increasing effects were diminished by longer pause requirements.
• Drug effects on local responding were consistently related to control response rates.

Conclusions:

• Control response rate is a critical determinant of drug effects, independent of reinforcement density.
• Environmental factors, such as response-spacing requirements, can modulate the extent of drug-induced rate changes.
• These findings highlight the importance of considering baseline response rate in behavioral pharmacology studies.