Meal schedule influences food restriction-induced locomotor sensitization to methamphetamine

Abstract

Traditional protocols for inducing sensitization to psychostimulants use an intermittent or "binge"-like drug administration, and binge eating behavior is comorbid with drug abuse in humans. Food restriction increases the reinforcing properties and self-administration of many drugs of abuse. The present study tested the hypotheses that (1) food restriction induces sensitization to the locomotor stimulation observed in response to methamphetamine and (2) a binge-like feeding schedule during food restriction produces increased sensitization compared to equally restricted mice fed in three daily meals. Male DBA/2J mice were fed ad libitum or were food restricted to either an 8% or 16% loss of body weight. Additionally, the food-restricted mice were divided into two groups that were fed in either one meal (binge) or three equal-sized meals (meal). After the reduced body weight was stable, mice were tested for locomotor activity following saline and methamphetamine (1 mg/kg) injections. Both 16% body weight loss groups exhibited sensitization to methamphetamine. Opposite to our hypothesis, the 8% meal but not the 8% binge food-restricted group demonstrated locomotor sensitization. Serum corticosterone levels were significantly higher in the meal-fed groups when compared to the binge- and ad libitum-fed groups. These results support a role for feeding schedule and plasma corticosterone levels in food restriction-induced enhancement of the effects of methamphetamine.