Differences in platelet serotonin transporter sites between African-American tobacco smokers and non-smokers

The serotonin transporter (5HTT) regulates the magnitude and duration of serotonergic neurotransmission. Although nicotine and other constituents of tobacco smoke may influence serotonin turnover among animals, few studies have examined whether smoking is associated with alteration in 5HTT in humans.

We investigated whether tobacco smokers and non-smokers differed in platelet tritiated paroxetine binding, a measure of 5HTT sites, and whether severity of nicotine dependence (ND) was related to 5HTT measures.

Tritiated paroxetine binding sites on platelets were assayed in 26 African-American smokers and 30 non-smokers. Severity of smoking was assessed using the Fagerstrom Test for Nicotine Dependence (FTND). Relationships between FTND scores and maximum number of transporter sites (B(max)) and affinity constant (K(d)) of paroxetine binding were determined.

B(max) values showed a significant negative correlation with FTND scores (rho=-0.28, P<0.01). Notably, smokers with higher ND had significantly lower B(max) compared to those with lower ND and non-smokers; the latter two groups did not differ in B(max) ( F=3.92, P<0.05). Smokers scored higher on impulsivity than non-smokers, however, behavioral variables did not influence the relationship of smoking with B(max). Age, gender and K(d) values were not associated with smoking or B(max).

Smoking, in particular higher nicotine dependence, appears to be correlated with decreased density of platelet 5HTT sites in African-Americans. The nature of the relationship and whether similar changes occur in the brain merit further investigation.