Correlations for serotonin levels and measures of mood in a nonclinical sample.

The Beck Depression Inventory is frequently used to detect depression and its severity because depression is a prevalent mood disorder and is commonly treated by prescription of selective serotonin-reuptake inhibitors such as Prozac. The importance of serotonin (5-HT) in the treatment of major depression is evident but the nature of this involvement is unclear. In this study, the characteristics of platelets are employed as a peripheral model of the neuron to estimate central serotonergic activity, which is a consequence of numerous factors including 5-HT2 receptor sensitivity. The greater the sensitivity of the platelet serotonin receptors, the lower the concentration of serotonin required to mobilise a particular amount of calcium from internal stores through serotonin stimulation. Hence, Platelet 5-HT2 receptor sensitivity is inferred from the concentration of serotonin that is required to produce half maximal intracellular calcium mobilisation (EC50). In the present study, the correlation of -.422 between scores on the Beck Depression Inventory and EC50 in a sample of 49 university students was significant, implying that mood is significantly related to 5-HT2 receptor sensitivity, such that increases in depressed mood are accompanied by increases in 5-HT2 receptor sensitivity.

Relationship between serotonin and the temperament and character inventory.

The unified biosocial theory of personality, proposed by Cloninger, conceptualises personality as a combination of heritable, neurobiologically based traits (temperament dimensions), and traits reflecting sociocultural learning (character dimensions). The temperament dimensions are thought to be related to activity in specific central neurotransmitter systems. The relationship of the dimensions of the Temperament and Character Inventory, particularly harm avoidance (HA), and platelet 5-HT2 receptor sensitivity was investigated in a sample of undergraduate student volunteers (N = 49). Serotonin-receptor binding results in Ca2+ release from intracellular stores. The concentration of serotonin required to produce half maximal Ca2+ response (EC50) is indicative of 5-HT2 receptor sensitivity such that the lower the EC50 serotonin concentration, the greater the 5-HT2 receptor sensitivity. A significant inverse correlation was found between HA and EC50 (r = -0.644, P < 0.001). Self-directedness was also significantly correlated with EC50 (r = 0.391, P = 0.005). Novelty seeking, a personality trait similar to sensation seeking, was not significantly correlated with serotonin.