Decreased reuptake of serotonin in human platelets after surgery

We have documented earlier a decrease in platelet serotonin and a concurren t increase in plasma serotonin, 5-hydroxytryptamin (5-HT) after various for ms of stress, suggesting a disturbed platelet 5-HT reuptake mechanism follo wing stress. In order to further elucidate these findings, we have studied platelet 5-HT reuptake kinetics (V-max and K-m) in nine patients before and 4 days after major, uncomplicated abdominal surgery. We found a significan t decrease in the maximal 5-HT reuptake velocity (V-max) after surgery and changes in K-m, verifying alterations in the affinity of the platelet 5-HT transport system. The present results thus confirm the hypothesis that 5-HT reuptake kinetics are altered following adrenergic hyperactivity. A decrea se in platelet 5-HT reuptake may bear implications for our understanding of poststress adaptive changes in the cardiovascular system as well as in the central nervous system (CNS) serotonergic neurones following stressful sti mulation.