title: Glycogen synthase kinase-3β inhibition in the medial prefrontal cortex mediates paradoxical amphetamine action in a mouse model of ADHD.
abstract: Psychostimulants show therapeutic efficacy in the treatment of attention-deficit hyperactivity disorder (ADHD). It is generally assumed that they ameliorate ADHD symptoms via interfering with monoaminergic signaling. We combined behavioral pharmacology, neurochemistry and molecular analyses to identify mechanisms underlying the paradoxical calming effect of amphetamine in low trait anxiety behavior (LAB) mice, a novel multigenetic animal model of ADHD. Amphetamine (1 mg/kg) and methylphenidate (10 mg/kg) elicited similar dopamine and norepinephrine release in the medial prefrontal cortex (mPFC) and in the striatum of LAB mice. In contrast, amphetamine decreased, while methylphenidate increased locomotor activity. This argues against changes in dopamine and/or norepinephrine release as mediators of amphetamine paradoxical effects. Instead, the calming activity of amphetamine corresponded to the inhibition of glycogen synthase kinase 3β (GSK3β) activity, specifically in the mPFC. Accordingly, not only systemic administration of the GSK3β inhibitor TDZD-8 (20 mg/kg), but also local microinjections of TDZD-8 and amphetamine into the mPFC, but not into the striatum, decreased locomotor activity in LAB mice. Amphetamine effects seem to depend on NMDA receptor signaling, since pre- or co-treatment with MK-801 (0.3 mg/kg) abolished the effects of amphetamine (1 mg/kg) on the locomotion and on the phosphorylation of GSK3β at the level of the mPFC. Taken together, the paradoxical calming effect of amphetamine in hyperactive LAB mice concurs with a decreased GSK3β activity in the mPFC. This effect appears to be independent of dopamine or norepinephrine release, but contingent on NMDA receptor signaling.
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Yi-Chun
authors: YC
authors: Yen
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Nils C
authors: NC
authors: Gassen
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Andreas
authors: A
authors: Zellner
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Theo
authors: T
authors: Rein
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Rainer
authors: R
authors: Landgraf
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Carsten T
authors: CT
authors: Wotjak
authors: Max Planck Institute of Psychiatry Munich, Germany.
authors: Elmira
authors: E
authors: Anderzhanova
keywords: ADHD; GSK3β; NMDA receptor; amphetamine; dopamine; mouse models; prefrontal cortex