Related Experiment Videos
Three-choice discrimination in pigeons is based on relative efficacy differences among opioids
E A Walker1, M J Picker, L A Dykstra
1Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. walkere@aehn2.einstein.edu
Psychopharmacology
|July 10, 2001
Summary
Opioid drug discrimination in pigeons reveals that the ability to distinguish between morphine and nalbuphine primarily relies on their differing relative efficacies. This finding aids in understanding opioid receptor selectivity and characterization.
Area of Science:
- Pharmacology
- Behavioral Neuroscience
Background:
- Drug discrimination assays are crucial for assessing opioid receptor selectivity and relative efficacy.
- Understanding these properties guides the classification and characterization of opioid agonists.
Purpose of the Study:
- To establish a three-choice discrimination task in pigeons differentiating between high-efficacy morphine, low-efficacy nalbuphine, and saline.
- To investigate if relative efficacy differences serve as a basis for stimulus control in opioid discrimination.
Main Methods:
- Seven pigeons were trained under fixed ratio 30 schedules to discriminate between nalbuphine, morphine, and saline.
- Substitution and antagonism experiments were conducted using various opioid agonists and naltrexone.
Main Results:
- Morphine and nalbuphine dose-dependently produced appropriate responding, indicating successful discrimination.
- Substitution tests showed that other opioids produced responding consistent with their known relative efficacies, differentiating between morphine- and nalbuphine-like stimulus effects.
- Naltrexone reversed the stimulus effects of both morphine and nalbuphine, confirming mu-opioid receptor involvement.
Conclusions:
- Pigeon drug discrimination effectively distinguishes between mu-opioid agonists based on relative efficacy.
- The study confirms that differences in relative efficacy are a primary determinant for stimulus control in this morphine-nalbuphine discrimination model.