Thalamic glutamate decreases with cigarette smoking

Rationale Findings from animal studies and human PET imaging indicate that nicotine and cigarette smoking affect glutamate (Glu) and related neurochemical markers in the brain and imply that smoking reduces extracellular Glu. As Glu release is mediated by nicotinic acetylcholine receptors (nAChRs), which are present at high concentrations in the thalamus, we examined the effects of smoking on thalamic Glu. Objective To determine the effects of tobacco smoking on thalamic glutamate levels. Methods Thalamic Glu levels were measured in vivo in 18 smokers and 16 nonsmokers using proton magnetic resonance spectroscopic imaging ( 1 H MRSI) at 1.5 T. Results Mean Glu levels did not differ significantly between the subject groups. However, within smokers, Glu levels were negatively correlated with self-reports of both cigarettes/day over the last 30 days ( r = −0.64, p = 0.006) and pack-years of smoking ( r = −0.66, p = 0.005). Conclusions Consistent with expectations based on preclinical studies, within smokers, cigarettes/day and pack-years are associated with reduced Glu in thalamus, a brain region rich in nAchRs. These results encourage work on candidate glutamatergic therapies for smoking cessation and suggest a noninvasive metric for their action in the brain.