Changes in feeding behavior after peripheral loperamide administration in rats.

Changes in the parameters of operant feeding behavior and body weight were studied in rats after intragastric administration of μ-opioid receptor agonist loperamide. Loperamide administration significantly suppressed foraging behavior in rats and reduced their body weight. Our findings suggest that peripheral loperamide administration, according to the hypothesis of reciprocal interactions between the central and peripheral parts of the endogenous opioid system, suppresses activity of central opioid mechanisms of feeding behavior organization. Changes in feeding behavior can appear due to disturbances in the mechanisms of assessment of food reward. We hypothesized that natural activation of μ-opioid receptors of the stomach with food-derived peptides can be associated with "sensory satiation" mechanism limiting excessive food intake.