Serotonin (5-HT)-stimulated intracellular Ca 2+ concentration change was studied in the platelets of healthy subjects, using fluorescent Ca indicator fura- 2. 5-HT increased the Ca 2+ response in a concentration- dependent manner. 10 μM of 5-HT induced the maximal response and its EC 5 0 value was 0.4 μM. This response was potently inhibited by selective 5-HT 2 antagonists, suggesting that 5-HT-induced Ca 2+ mobilization in human platelets is mediated by 5-HT 2 receptors. This 5-HT 2- mediated Ca 2+ response was not significantly affected by the time of blood sampling, gender, meal or exercise. However, this response declined with time after blood drawing, suggesting that it must be measured as soon as possible after sampling. These results indicate that 5-HT-stimulated Ca 2+ response in human platelets is a stable parameter and that it will be suitable for assessing 5-HT 2 receptor function in depressed patients.
Read full abstract