Serotonin transport kinetics correlated between human platelets and brain synaptosomes

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Blood platelets have been used extensively as a model system for investigating the role of the serotonin transporter (SERT) in various psychiatric disorders, especially depression. However, to date, it is not known whether platelet serotonin (5-HT) transport would be related to that in brain. We examined 5-HT transport kinetics simultaneously in human blood platelets and human cortical brain synaptosomes to determine whether they were correlated. Blood platelets and synaptosomes were obtained from 25 patients undergoing epileptic surgery. Synaptosomes were obtained from normal margins of surgical neuropathology specimens of anterotemporal cortex. Platelet SERT V(max) was significantly correlated with brain SERT V(max) on linear regression (r=0.58, p<0.005), after controlling for the confounding effects of gender (t=-2.4, p=0.025) and time of day (t=2.1, p<0.05). Consistent with previous observations, there was a negative correlation between the maximum velocity (V(max)) of platelet 5-HT transport and pO2 (r=-0.52, p<0.01). Females had a significantly higher pO2 than males (F=4.9, p<0.05). After accounting for gender differences, addition of pO2 did not add further strength to the regression, given the aforementioned gender differences in pO2. The correlation between unadjusted values for platelet vs brain SERT V(max) was r=0.3, p=0.06. These results suggest that a relationship may exist between 5-HT transport in platelets and cortical synaptosomes, when appropriate controls for confounding factors are employed.