Sensitization to cocaine in pigeons: interaction with an operant contingency

Area of Science:

• Behavioral neuroscience
• Pharmacology
• Animal behavior

Background:

• Cocaine exposure can lead to behavioral sensitization, an increase in locomotor activity with repeated administration.
• The influence of learned behaviors, such as operant conditioning, on drug-induced sensitization is not fully understood.

Purpose of the Study:

• To investigate how an explicit operant contingency affects cocaine-induced locomotor activity and sensitization in pigeons.
• To determine if learned behaviors can modulate the development of behavioral sensitization to cocaine.

Main Methods:

• A two-part study using pigeons exposed to a fixed-ratio-20 schedule of food presentation (Part 1) or no food schedule (Part 2).
• Pigeons received daily administrations of a locomotion-increasing dose of cocaine after initial effects were determined.
• Locomotor activity and key pecking behavior were monitored to assess sensitization and tolerance.

Main Results:

• Pigeons in Part 2 (no food schedule) exhibited clear locomotor sensitization to cocaine.
• Pigeons in Part 1 (food schedule) developed tolerance to cocaine's effects on key pecking.
• Locomotor sensitization was largely absent in pigeons from Part 1, suggesting an interaction between operant behavior and drug effects.

Conclusions:

• Explicitly conditioned operant behavior may compete with, and thus inhibit, behavioral sensitization induced by repeated cocaine exposure.
• Learned behaviors can play a significant role in modulating the neurobiological effects of psychostimulant drugs like cocaine.