title: Neuroplasticity in cigarette smokers is altered under withdrawal and partially restituted by nicotine exposition.
abstract: Nicotine improves cognitive functions by modulating neuroplasticity and cortical excitability in nonsmoking subjects. As shown recently, the positive effect of nicotine on cognition might at least partially be caused by a focusing effect of nicotine on neuroplasticity in these subjects. Concordant to this, smokers under nicotine withdrawal show reduced cognitive abilities, which are at least partially restituted by nicotine consumption. We aimed to explore the neurophysiological foundation of these effects by exploring nonfocal and focal plasticity-inducing protocols in human smokers under nicotine withdrawal and exposition. Focal, synapse-specific plasticity was induced by paired associative stimulation (PAS), while nonfocal plasticity was induced by transcranial direct current stimulation (tDCS). Each subject (12) received placebo and nicotine patches combined with one of the stimulation protocols to the primary motor cortex. Corticospinal excitability was monitored by transcranial magnetic stimulation-induced motor-evoked potential amplitudes. In smokers during nicotine withdrawal, facilitatory plasticity induced by tDCS and PAS was abolished, but restituted by nicotine. In contrast, excitability-diminishing plasticity was not affected by nicotine withdrawal. Under nicotine, the inhibitory aftereffects of PAS were delayed and prolonged, while the tDCS-generated excitability reduction was abolished. Thus, absent facilitatory plasticity in smokers during nicotine withdrawal is restituted by nicotine, favoring the deficit-compensating hypothesis of nicotine consumption. These results might shed further light on the proposed mechanism of nicotine on cognition and attention, which might be connected to nicotine addiction and probability of relapse in smokers.
authors.affiliation: Georg-August University, Department of Clinical Neurophysiology, Göttingen, Germany. jgrundey@med.uni-goettingen.de
authors.forename: Jessica
authors.initials: J
authors.lastname: Grundey
authors.forename: Nivethida
authors.initials: N
authors.lastname: Thirugnanasambandam
authors.forename: Kim
authors.initials: K
authors.lastname: Kaminsky
authors.forename: Anne
authors.initials: A
authors.lastname: Drees
authors.forename: Angela C
authors.initials: AC
authors.lastname: Skwirba
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lang
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
authors.forename: Michael A
authors.initials: MA
authors.lastname: Nitsche
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004311:Double-Blind Method; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology*; D009473:Neuronal Plasticity / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D012907:Smoking / Q000473:pathology* / Q000628:therapy; D061485:Tobacco Use Cessation Devices; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine