Adolescent Oral Methylphenidate Treatment Causes Post-administration Increase in Weight Gain and Hyperphagia with no Effect on Anxiety-related Behaviours in Rats

Methylphenidate (MPH) is a widely abused drug that has been shown to be a neural stimulant, amidst concern that it could be neurotoxic. The present study evaluated the changes in body weight, food intake and anxiety-related behaviours following oral administration of MPH to adolescent rats. Thirty- two (32) male adolescent wistar rats were divided into two groups and orally administered either saline vehicle or MPH from post-natal day (PD) 30 twice daily for 14 days. Body weight and food intake were monitored during administration and post-administration periods till PD 70. Anxiety-related activities were assessed using open-field (OF) and elevated plus maze (EPM) task on PD 45 and 70. Animals that received oral MPH administration showed significant decrease in weight gain but average food intake was not altered significantly during administration period. On the other hand, following discontinuation of MPH administration, treated rats recorded a significant increase in weight gain and average food intake. There was no significant treatment effect on central locomotion and time spent in open arms, which are indices of anxiety in the OF and EPM respectively. The study suggests that cessation of oral MPH treatments may induce a post-administration hyperphagia and a resultant effect of increased rate of weight gain. Also, the findings did not show anxiety modulatory actions of MPH following oral administration.