Early methylphenidate exposure enhances cocaine self-administration but not cocaine-induced conditioned place preference in young adult rats.

Rationale: Previous studies in rodents show that early exposure to methylphenidate alters later responsiveness to drugs of abuse. An interesting feature of these studies is that early methylphenidate treatment decreases the rewarding value of cocaine when measured by conditioned place preference (CPP), but the same treatment increases cocaine self-administration.

Objective: The goal of the present study was to examine the effects of early methylphenidate exposure on cocaine-induced responding using both reward paradigms.