Background:Our previous studies have demonstrated that the levels of 5-hydroxytryptamine (5-HT) and 5-HT 2A receptor (5-HT2AR) in serum and platelet were associated with depression and myocardial infarction (MI),and pretreatment with ginseng fruit saponins (GFS) before MI and depression had an effect on the 5-HT system.In this study,the effects of GFS on the 5-HT system in the Sprague-Dawley (SD) rats with MI,depression,and MI + depression were evaluated.Methods:A total of eighty SD rats were allocated to four groups:MI,depression,MI + depression,and control groups (n =20 in each group).Each group included two subgroups (n =10 in each subgroup):Saline treatment subgroup and GFS treatment subgroup.The levels of5-HT,5-HT2AR,and serotonin transporter (SERT) were quantified in serum,platelet lysate,and brain tissue through the enzyme-linked immunosorbent assay method,respectively.Results:Compared with those in the saline treatment subgroups,the levels of 5-HT in serum and platelet lysate statistically significantly increased in the GFS treatment subgroups of MI,depression,and MI + depression groups (serum:all P =0.000;platelet lysate:P =0.002,0.000,0.000,respectively).However,the 5-HT levels in brain homogenate significantly decreased in the GFS treatment subgroups compared with those in the saline treatment subgroups in MI and depression groups (P =0.025 and 0.044 respectively),and no significant difference was observed between saline and GFS treatment subgroups in MI + depression group (P =0.663).Compared with that in GFS treatment subgroup of control group,the 5-HT2AR levels in the platelet lysate significantly decreased in GFS treatment subgroups of MI,depression,and MI + depression groups (all P=0.000).Compared to those in the saline treatment subgroups,the serum SERT levels significantly decreased in the GFS treatment subgroups in MI,depression,and MI + depression groups (P =0.009,0.038,and P=0.001,respectively),while the SERT levels ofplatelet lysate significantly decreased in GFS treatment subgroup of MI group (P =0.000),significantly increased in GFS treatment subgroup of depression group (P =0.019),and slightly changed in GFS treatment subgroup ofMI + depression group (P =0.219).No significant changes for SERT levels in brain homogenate could be found between the saline and GFS treatment subgroups in MI,depression,and MI + depression groups (P =0.421,0.076 and P =0.642).Conclusions:This study indicated that GFS might inhibit the reuptake of 5-HT from serum to platelet according to decreased 5-HT2AR in platelet and SERT in serum and platelet.The change of 5-HT in serum after GFS treatment was inconsistent with that in the brain.It seemed that GFS could not pass through the blood-brain barrier to affect the central serotonergic system.