Vmax values for 5-HT uptake among genotypes for the 5-HTT. Genotype and Vmax values for 5-HT uptake were determined as described in Methods. Vmax was expressed as fmol 5-HT/min-107 platelets. Mean±S.E.M. of Vmax values for 5-HT uptake for LL, LS, and SS subjects were 409±76 (N=33), 434±57 (N=56), and 390±62 (N=22), respectively. The percentages of Vmax values below 200 fmol/min-107 platelets among the LL, LS, and SS genotypes were 51.5%, 39.3%, and 22.7%, respectively (LL vs. SS, P<0.05).