Effect of eseroline on schedule-controlled behavior in the rat

Area of Science:

• Pharmacology
• Neuroscience
• Behavioral Science

Background:

• Eseroline, a hydrolysis product of eserine, is a potent analgesic with weak anticholinesterase activity.
• Understanding the behavioral effects of analgesic agents is crucial for their therapeutic application.

Purpose of the Study:

• To investigate the effects of eseroline on operant behavior in male Sprague-Dawley rats.
• To explore the receptor mechanisms underlying eseroline's behavioral effects, specifically the involvement of opiate and muscarinic receptors.

Main Methods:

• Rats were trained on a fixed-ratio (FR) 20 schedule with time-out periods for lever pressing to obtain water reinforcement.
• Eseroline was administered subcutaneously at doses ranging from 0.25 to 8 mg/kg.
• The effects of eseroline were assessed by measuring the number of reinforcements and response patterns during a 120-min test session.
• The role of opiate and muscarinic receptors was investigated through coadministration with naloxone and atropine, respectively.

Main Results:

• Eseroline produced a dose-dependent decrease in the number of reinforcements, with significant effects observed at doses of 1, 2, 4, and 8 mg/kg (ED50 = 2.5 mg/kg).
• Behavioral disruption was characterized by rapid pausing post-dosing and gradual recovery.
• The duration of eseroline's rate-decreasing effects was dose-related and longer than previously reported for its antinociceptive effects.
• Naloxone antagonized eseroline's effects on operant behavior, while atropine did not.

Conclusions:

• The behavioral effects of eseroline are consistent with its antinociceptive properties.
• These findings suggest that eseroline's actions on operant behavior are mediated through the activation of opiate receptors.
• The results indicate that eseroline's effects are not related to the stimulation of muscarinic receptors via its anticholinesterase activity.