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Animal model of methylphenidate's long-term memory-enhancing effects
Stephanie A Carmack1, Kristin K Howell, Kleou Rasaei
1Molecular Cognition Laboratory, Department of Psychology, University of California, San Diego, California 92093-0109, USA.
Learning & Memory (Cold Spring Harbor, N.Y.)
|January 18, 2014
Summary
Methylphenidate (MPH) enhances long-term memory (LTM) at low doses, but impairs it at high doses. This study used fear conditioning to model MPH
Area of Science:
- Neuroscience
- Pharmacology
- Psychiatry
Background:
- Methylphenidate (MPH) is a widely prescribed medication for attention deficit hyperactivity disorder (ADHD).
- While MPH's effects on executive function are well-studied, its impact on long-term memory (LTM) remains less understood, despite LTM improvement being a therapeutic goal in ADHD.
- Pavlovian fear conditioning serves as a key model for investigating memory processes.
Purpose of the Study:
- To investigate the dose-dependent effects of Methylphenidate (MPH) on long-term memory (LTM) using a fear conditioning paradigm.
- To compare MPH's effects with those of other ADHD medications, including atomoxetine, bupropion, and citalopram.
- To explore the neurochemical underpinnings and addictive potential of MPH in relation to its memory effects.
Main Methods:
- Administered a range of MPH doses (0.01-10 mg/kg) to assess fear memory in a validated animal model.
- Compared MPH's effects to those of atomoxetine, bupropion, and citalopram across various doses.
- Evaluated MPH's influence on locomotion and anxiety to rule out confounding factors.
- Assessed the role of dopamine and norepinephrine transporter inhibition in MPH-induced memory enhancement.
- Compared the addictive potential of MPH with amphetamine and cocaine using conditioned place preference and behavioral sensitization.
Main Results:
- Low, clinically relevant doses of MPH enhanced fear memory, while high doses impaired it.
- MPH's memory-enhancing effects were independent of its impact on locomotion and anxiety.
- Dopamine and norepinephrine transporter inhibition were necessary for MPH-induced memory enhancement.
- Memory-enhancing effects of psychostimulants at low doses were distinct from their reinforcing and locomotor-activating effects at high doses.
Conclusions:
- Fear conditioning is a valuable model for studying psychostimulant effects on LTM in drug development.
- MPH exhibits a dose-dependent effect on memory, enhancing it at low doses and impairing it at high doses.
- The findings suggest a dissociation between the therapeutic memory-enhancing effects of psychostimulants and their potential for abuse.
