Mitragynine reduces methamphetamine self-administration in rats without disrupting food-maintained responding

Area of Science:

• Neuroscience
• Pharmacology
• Addiction Research

Background:

• Kratom (Mitragyna speciosa) is increasingly used for substance use disorders (SUD).
• Mitragynine (MG) is the primary psychoactive alkaloid in kratom.
• Preclinical research is needed to validate kratom's therapeutic potential.

Purpose of the Study:

• To determine if MG reduces methamphetamine self-administration in rats.
• To assess MG's effects on food-maintained responding.
• To investigate MG's efficacy under fixed-ratio and progressive-ratio schedules.

Main Methods:

• Male and female Sprague-Dawley rats self-administered methamphetamine or food pellets.
• Rats received intraperitoneal injections of MG (10-56 mg/kg) or vehicle prior to testing.
• Behavioral outcomes included lever presses, response rates, and progressive-ratio breakpoints.

Main Results:

• MG dose-dependently decreased methamphetamine self-administration under both fixed-ratio and progressive-ratio schedules.
• Significant reductions in lever presses and breakpoints were observed at 32 and 56 mg/kg MG.
• MG's effects on methamphetamine self-administration were comparable between sexes and did not alter food-maintained responding.

Conclusions:

• MG selectively reduces methamphetamine reinforcement at doses that do not affect natural rewards like food.
• These findings highlight MG's potential as a therapeutic agent for methamphetamine use disorder.
• Further preclinical evaluation of MG for SUD treatment is warranted.