Inhibition of monoamine oxidase B in the brains of smokers

Abstract

The massive health problem associated with cigarette smoking is exacerbated by the addictive properties of tobacco smoke and the limited success of current approaches to cessation of smoking. Yet little is known about the neuropharmacological actions of cigarette smoke that contribute to smoking behaviour, or why smoking is so prevalent in psychiatric disorders and is associated with a decreased risk of Parkinson's disease. Here we report that brains of living smokers show a 40% decrease in the level of monoamine oxidase B (MAO B; EC 1.4.3.4) relative to non-smokers or former smokers. MAO B is involved in the breakdown of dopamine, a neurotransmitter implicated in reinforcing and motivating behaviours as well as movement. MAO B inhibition is therefore associated with enhanced activity of dopamine, as well as with decreased production of hydrogen peroxide, a source of reactive oxygen species. We propose that reduction of MAO B activity may synergize with nicotine to produce the diverse behavioural and epidemiological effects of smoking.

Functional brain imaging of tobacco use and dependence

“…Fowler and colleagues have performed a series of elegant studies demonstrating decreases in monoamine oxidase (MAO) A and B activity in cigarette smokers using the PET tracers [ 11 C] clorgyline (Fowler et al, 1996b) and ([ 11 C]L-deprenyl-D2) (Fowler et al, 1996a(Fowler et al, , 1998b, respectively. When compared to former smokers and non-smokers, average reductions for current smokers are 30% and 40% for MAO A and B (Fowler et al, 2003a).…”

Long-term Effects of Adolescent Smoking on Depression and Socioeconomic Status in Adulthood in an Urban African American Cohort

“…Lastly, it may also be that the potentially drug-induced negative effect of nicotine on mood regulation was mediated or mitigated by unhealthy behaviors, such as smoking itself or using other substances and overeating. [14][15][16][17] Other research has hypothesized that engaging in unhealthy behaviors, such as smoking and overeating, may be one of the coping methods for African Americans in response to day-to-day stressful conditions, such as poverty or crime. 64 Yet, we need future research to examine the role of stress and unhealthy behaviors as coping mechanisms in the pathways of smoking and depression in this population.…”

“…This alteration of neurochemicals may in turn affect mood regulation and may be an etiology for major depression. [14][15][16][17] Another potential mechanism that may explain the causal effect of cigarette smoking on depression is via psychosocial factors such as rebelliousness. Albers and Biener tested rebelliousness in the pathway and found rebelliousness-measured by several domains related to adolescent problem behaviors-accounted for the association between smoking and depressive symptoms.…”

Brazilian plants with possible action on the central nervous system—A study of historical sources from the 16th to 19th century

“…neuroprotective (Qiao et al, 2005); improves cognition (Maskos et al, 2005), increases sensibility of behavioral effects of alcohol (Bowers et al, 2005); decreases sensibility to metanphetamine (Kuribara, 1999); increases dopaminergic activity (Pidoplichko et al, 1997); act on cholinergic receptors (Kobayashi et al, 1999); inhibits MAO B (Fowler et al, 1996); psychoactive (Cassels et al, 2005 stimulant, tonic (Dr. Duke, 2010) tonic (Mendes & Carlini, 2007). antioxidant (Basile et al, 2005), psychostimulant (Otobone et al, 2007).…”