18-Methoxycoronaridine: A potential new treatment for obesity in rats?

Rationale: Excessive eating often leads to obesity. Although a variety of neurotransmitters and brain regions are involved in modulating food intake, a role of accumbal dopamine is thought to be critical for several aspects of this behavior. Since 18-methoxycoronaridine (18-MC), a selective antagonist of α3β4 nicotinic receptors, was previously shown to alter dopamine release in the nucleus accumbens in response to chronic injections of cocaine and morphine, this drug could be a promising therapy for abnormal eating behavior. Objectives: Assess the effect of 18-MC on the consumption of sucrose (15%) vs. water in a self-administration paradigm and on the intake of freely available palatable fluids (i.e., 5% sucrose, 0.1% saccharin, and 0.6% saline solutions) as well as on water intake. Determine whether repeated administration of 18-MC (20 mg/kg i.p.) affects weight gain, food intake, and fat deposition in rats drinking 30% sucrose solution. Results: Acute administration of 18-MC (10-40 mg/kg i.p.) reduced operant responding for sucrose and decreased ad libitum ingestion of sucrose, saccharin, and saline. The highest dose of 18-MC also reduced consumption of water when palatable fluids were not available. In rats having unlimited access to sucrose (30%), chronic treatment with 18-MC (20 mg/kg i.p.) prevented sucrose-induced increases in body weight, decreased fat deposition, and reduced consumption of sucrose while not altering food intake. Conclusions: These data suggest that antagonism of α3β4 nicotinic receptors may be involved in the regulation of intake of palatable substances regardless of its caloric value and may participate in maintaining obesity.