Monlunabant suppresses appetite through a central mechanism

Area of Science:

• Neuroscience
• Pharmacology
• Obesity Research

Background:

• The cannabinoid receptor 1 (CB 1 ) antagonist, monlunabant, was developed to treat obesity by targeting peripheral receptors.
• Previous CB 1 antagonists, like rimonabant, showed efficacy but carried risks of adverse psychiatric effects.
• The precise mechanism of action for monlunabant, particularly the involvement of central versus peripheral CB 1 receptors, remained unclear.

Purpose of the Study:

• To investigate whether monlunabant exerts its appetite-suppressing effects via central nervous system CB 1 receptors.
• To compare the potency of monlunabant and rimonabant in modulating CB 1 receptor activity in vivo.
• To assess the potential for central CB 1 receptor antagonism by monlunabant and its implications for adverse effects.

Main Methods:

• Adult male mice were used to assess the effects of monlunabant and rimonabant on appetite and hypothermia.
• CB 1 agonist-induced hypothermia was used as a model to evaluate receptor antagonism.
• Appetite suppression was measured in food-deprived mice with limited access to preferred food.

Main Results:

• Both monlunabant and rimonabant reduced appetite and antagonized CB 1 agonist-induced hypothermia in mice.
• Monlunabant was consistently less potent than rimonabant in both observed effects.
• Appetite suppression was observed at doses of monlunabant that likely involved central CB 1 receptor antagonism, not peripheral saturation.

Conclusions:

• Monlunabant's appetite-suppressing effects are primarily mediated through the antagonism of central CB 1 receptors.
• The findings suggest that monlunabant may share similar risks of adverse psychiatric effects with rimonabant.
• Second-generation CB 1 antagonists developed for obesity warrant careful evaluation for central nervous system-related side effects.