Opioid drugs like meperidine are frequently used for pain management.
Understanding the behavioral effects and mechanisms of opioids is crucial for clinical practice.
Purpose of the Study:
To investigate the dose-dependent effects of meperidine on operant responding in pigeons.
To examine the potential antagonism of meperidine's effects by opioid antagonists and cross-tolerance with methadone.
Main Methods:
Pigeons were trained on a multiple fixed-ratio, fixed-interval schedule of food presentation.
Meperidine was administered at various doses, and its effects on response rates were recorded.
Naloxone, cyclazocine, and methadone were used to assess antagonism and cross-tolerance.
Main Results:
Low doses of meperidine increased responding under the fixed-interval schedule, while higher doses decreased responding under both fixed-ratio and fixed-interval schedules.
Naloxone partially antagonized the rate-increasing effects of meperidine, but neither naloxone nor cyclazocine antagonized the rate-decreasing effects.
Meperidine did not exhibit cross-tolerance with methadone, indicating distinct pharmacological mechanisms.
Conclusions:
The rate-decreasing effects of meperidine are not mediated by typical opioid receptors targeted by naloxone and cyclazocine.
Meperidine's distinct pharmacological profile suggests it may not share the same tolerance development pathways as methadone.