Four-choice drug discrimination in pigeons

Area of Science:

• Behavioral pharmacology
• Neuroscience
• Drug discrimination studies

Background:

• Pigeons were trained to discriminate between pentobarbital, morphine, and saline.
• A four-choice procedure was employed to expand drug discrimination capabilities.

Purpose of the Study:

• To investigate the discriminative stimulus effects of (+)amphetamine in a four-choice drug discrimination task.
• To assess drug generalization patterns with a more complex discrimination paradigm.
• To evaluate the utility of the four-choice procedure for studying multiple receptor interactions and drug mixtures.

Main Methods:

• Pigeons were trained on a three-choice drug discrimination task and (+)amphetamine was added as a fourth stimulus.
• Generalization tests were conducted with various drugs, including chlordiazepoxide, methadone, cocaine, methamphetamine, and phencyclidine.
• Dose-response curves were determined using both single-dose and cumulative-dosing procedures.

Main Results:

• Pigeons quickly acquired the four-choice drug discrimination.
• Observed generalization patterns were consistent with simpler discrimination tasks: pentobarbital generalized to chlordiazepoxide, morphine to methadone, and (+)amphetamine to cocaine and methamphetamine.
• Phencyclidine showed dose-dependent generalization to saline at low doses and to pentobarbital and (+)amphetamine at higher doses.
• Dose-response curves were quantal and consistent across single-dose and cumulative-dosing methods.

Conclusions:

• The four-choice drug discrimination procedure is effective for training complex stimulus control.
• This method accurately reflects known drug generalization patterns and is suitable for studying drugs acting on multiple receptor subtypes.
• The four-choice procedure provides advantages for investigating the discriminative effects of drug mixtures.