Effects of monoaminergic drugs on training -induced motor cortex plasticity in older adults

• Type of Material: Article
• Authors: Trisha M. Kesar, Emory University; Samir R Belagaje, Emory University; Paola Pergami, West Virginia University; Marc W. Haut, West Virginia University; Gerald Hobbs, West Virginia University; Cathrin Buetefisch, Emory University
• Language: English
• Date: 2017-09-01
• Publisher: Elsevier: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2017 Elsevier B.V.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.brainres.2017.06.015
• Title of Journal or Parent Work: Brain Research
• ISSN: 0006-8993
• Volume: 1670
• Start Page: 106
• End Page: 117
• Grant/Funding Information: Dr. Kesar was supported by National Institutes of Health award number K01HD079584.; The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.; Research reported in this publication was supported by the National Institute of Neurological Disorders And Stroke of the National Institutes of Health under Award Number R01NS060830, R56NS070879, R21HD067906, R01NS090677.
• Keywords: RECOVERY; Neurosciences; DOUBLE-BLIND; D-AMPHETAMINE; Life Sciences & Biomedicine; LONG-TERM POTENTIATION; Transcranial magnetic stimulation; Science & Technology; AGE-RELATED-CHANGES; Neurosciences & Neurology; Monoaminergic drugs; USE-DEPENDENT PLASTICITY; TRANSCRANIAL MAGNETIC STIMULATION; CHRONIC STROKE; Motor evoked potential; PAIRED ASSOCIATIVE STIMULATION; Motor cortex; PREFRONTAL CORTEX
• Research Categories: Health Sciences, Radiology; Health Sciences, Medicine and Surgery

Abstract

Primary motor cortex (M1) plasticity is involved in motor learning and stroke motor recovery, and enhanced by increasing monoaminergic transmission. Age impacts these processes but there is a paucity of systematic studies on the effects of monoaminergic drugs in older adults. Here, in ten older adults (age 61 + 4 years, 4 males), we determine the effects of a single oral dose of carbidopa/levodopa (DOPA), D-amphetamine (AMPH), methylphenidate (MEPH) and placebo (PLAC) on M1 excitability and motor training-induced M1 plasticity. M1 plasticity is defined as training related long lasting changes in M1 excitability and kinematics of the trained movement. At peak plasma level of the drugs, subjects trained wrist extension movements for 30 min. Outcome measures were motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation at increasing intensity (stimulus response curve, SRC) and peak acceleration of the trained wrist extension movements. Measures were obtained before and after completion of training. The curve parameters plateau (MEPmax), inflection point, and slope were extracted from SRC. At baseline drugs had a differential effect on curve parameters, while kinematics remained unchanged. Training alone (PLAC) increased MEPmax but did not improve kinematics. Drugs affected training-related changes of the curve parameters differently, but did not enhance them or kinematics when compared to PLAC. The results demonstrate that in the older adults, MEPH, DOPA, or AMPH have differential effects on baseline M1 excitability and training-related M1 plasticity but fail to enhance them above the naïve level.