title: The separate and combined effects of monoamine oxidase inhibition and nicotine on P50 sensory gating.
abstract: BACKGROUND
  The cognitive effects of nicotine in humans remain a topic of great interest, due to the continued prevalence of cigarette smoking in society as well as the hypothesis that cognitively impaired populations such as schizophrenia patients use nicotine as a means of self-medicating against deficits of sensory gating. However, chronic smoking can predispose individuals to robust monoamine oxidase (MAO) inhibition, and thus far, the effect of MAO inhibition on human sensory gating is unknown.
  
  
  METHODS
  In this study, we investigated the effects of both nicotine (6-mg gum) and pharmacologically induced MAO-A inhibition via moclobemide (75 mg) on P50 event-related potential-indexed sensory gating in a sample of 24 healthy non-smoking males.
  
  
  RESULTS
  Ratio score (rP50) measured gating revealed significant improvement in auditory stimulus suppression after combined nicotine and MAO-A inhibition compared to placebo and to the nicotine-alone condition. This nicotine + MAO-A inhibition-induced efficient gating was consistent regardless of participants' baseline (placebo) gating efficiency, despite the observation that nicotine in the absence of MAO-A inhibition exhibited a detrimental effect on gating in participants with high baseline suppression ratios.
  
  
  CONCLUSIONS
  Nicotine and monoamine oxidase-inhibiting agents in tobacco smoke appear to exert a synergistic effect on sensory gating, which may contribute to the elevated dependence rates seen in populations with cognitive deficits such as schizophrenia.
authors.affiliation: University of Ottawa Institute of Mental Health Research, 1145 Carling Ave., Ottawa, ON, Canada, K1Z 7K4, dylan.m.smith@gmail.com.
authors.forename: Dylan M
authors.initials: DM
authors.lastname: Smith
authors.forename: Derek
authors.initials: D
authors.lastname: Fisher
authors.forename: Pierre
authors.initials: P
authors.lastname: Blier
authors.forename: Vadim
authors.initials: V
authors.lastname: Illivitsky
authors.forename: Verner
authors.initials: V
authors.lastname: Knott
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D020912:Moclobemide / Q000494:pharmacology*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D009538:Nicotine / Q000494:pharmacology*; D012559:Schizophrenia / Q000503:physiopathology; D055139:Sensory Gating / Q000187:drug effects*; D012907:Smoking / Q000235:genetics; D061485:Tobacco Use Cessation Devices
chemical_list: D008996:Monoamine Oxidase Inhibitors; D009538:Nicotine; D020912:Moclobemide