Infusion of methylphenidate into the basolateral nucleus of amygdala or anterior cingulate cortex enhances fear memory consolidation in rats

Abstract

The psychostimulant methylphenidate (MPD; also called Ritalin) is a blocker of dopamine and norepinephrine transporter. It has been clinically used for treatment of Attention Deficit and Hyperactivity Disorder (ADHD). There have been inconsistent reports regarding the effects of systemically administered MPD on learning and memory, either in animals or humans. In the present study, we investigated the effect of direct infusion of MPD into the basolateral nucleus of amygdala (BLA) or the anterior cingulate cortex (ACC) on conditioned fear memory. Rats were trained on a one-trial step-through inhibitory avoidance task. MPD was infused bilaterally into the BLA or the ACC, either at '0' or 6 h post-training. Saline was administered as control. Memory retention was tested 48 h post-training. Intra-BLA or intra-ACC infusion of MPD '0' h but not 6 h post-training significantly improved 48-h memory retention: the MPD-treated rats had significant longer step-through latency than controls. The present results indicate that action of MPD in the BLA or the ACC produces a beneficial effect on the consolidation of inhibitory avoidance memory.