Posted on behalf of Neloy Kumar Chakroborty
Summary: Prefrontal cortex (PFC) is known to be an important area regulating the extinction of fear. Psychostimulants that can increase the extracellular levels of dopamine (DA) in the PFC were reported to be involved in the fear extinction, although the reports were dilemmatic. Methylphenidate hydrochloride (MPH) or Ritalin (trade name) was known to increase the extracellular levels of the DA and norepinephrine (NA) in the PFC and has been approved for the therapy of attention deficit hyperactivity disorder (ADHD). The authors in this article were trying to investigate the effect of the systemic injection of Ritalin both during the pre and post-session of the contextual fear extinction to the development and consolidation of the extinction memory in the mouse model. They found that pre-session injection of MPH had promoted the extinction learning during the training and test trials after 1 day, although the drug had an immediate effect of increasing the overall locomotor activity of animals. Administration of MPH immediately after the extinction session had enhanced the extinction effect over a period of 3 days of retention tests. However, this effect was most obvious with the dosage of 20 mg/kg, although the other doses (both higher and lower) had revealed the enhancement of the fear extinction. The enhancement of fear extinction was neither observer while the drug was applied 4 hours later than the extinction session nor while the time session of the extinction learning trial was shortened which was followed by the MPH injection. The authors had concluded that MPH can enhance the extinction of fear and that this effect was found to be sensitive to dose, time of injection, and duration of the extinction session. Because MPH is widely used in clinical treatments, these experiments had suggested that potential use of the drug in combination with the behavioral therapies for patients with fear disorders.
Reference:
Abraham AD, Cunningham CL, & Lattal KM (2012). Methylphenidate enhances extinction of contextual fear. Learning & memory (Cold Spring Harbor, N.Y.), 19 (2), 67-72 PMID: 22251891
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