Nicotinic acetylcholine receptors reduced in smokers with schizophrenia
MedWire News: Results from a US study show that patients with schizophrenia who are smokers have significantly less β2*-nicotinic acetylcholine receptor availability in the brain than mentally healthy smokers.
Furthermore, Deepak D'Souza (Yale University School of Medicine, New Haven, Connecticut) and team found a negative correlation between β2*-nicotinic acetylcholine receptor availability and negative symptoms.
"Individuals with schizophrenia have high rates of comorbid cigarette smoking and are more dependent on nicotine than other smokers," observe the researchers.
They explain: "Nicotinic acetylcholine receptors containing β2 subunits are abundant in the brain and have the highest affinity for nicotine. They are the most common subtype in striatal reward pathways and are critical in mediating the reinforcing effects of nicotine."
The team compared β2*-nicotinic acetylcholine receptor availability between 11 schizophrenia patients who were smokers and 11 age- and gender-matched mentally healthy smokers.
After refraining from smoking for at least 5 days, the participants underwent brain scans using single-photon emission computed tomography with a β2*-nicotinic acetylcholine receptor agonist radiotracer.
The researchers found that smokers with schizophrenia had significantly lower β2*-nicotinic acetylcholine receptor availability in the parietal cortex (21%), frontal cortex (26%), and thalamus (21%) compared with mentally healthy smokers.
There were no significant between-group differences for β2*-nicotinic acetylcholine receptor availability in the striatum and hippocampus.
They also found significant negative correlations between the availability of β2*-nicotinic acetylcholine receptors in the parietal cortex, frontal cortex, thalamus, striatum, and hippocampus, and negative symptom severity, as measured using the Positive and Negative Syndrome Scale and the Scale for the Assessment of Negative Symptoms.
There were no significant correlations between the number of cigarettes smoked per day and β2*-nicotinic acetylcholine receptor availability in either the smokers with schizophrenia or the mentally healthy smokers, the researchers note.
D'Souza and team conclude in the American Journal of Psychiatry: "This study provides the first in vivo evidence to our knowledge of lower β2*-nicotinic acetylcholine receptor availability and an inverse correlation between receptor availability and negative symptoms in smokers with schizophrenia."
They add: "Given the absence of any effective treatments for negative symptoms, the findings of this study suggest that medications targeting the β 2*-nicotinic acetylcholine receptor system may be effective."
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By Mark Cowen