Thermal balneotherapy induces changes of the platelet serotonin transporter in healthy subjects

Although the beneficial effects of balneotherapy have been recognized since a long time, a few information is available on the biological mechanisms underlying them and the subjective feelings of increased well-being and mood. The links between the serotonin (5-HT) system and mood prompted us to investigate the 5-HT platelet transporter (SERT), which is considered a reliable, peripheral marker of the same structure present in presynaptic neurons, in 20 healthy volunteers before (t0) and 30 min after (t1) thermal balneotherapy with ozonized water of Montecatini spa, as compared with a similar group who underwent a bath in non-mineral water. The SERT was evaluated by means of the specific binding of (3)H-paroxetine ((3)H-Par) to platelet membranes. Equilibrium-saturation binding data, the maximal binding capacity (Bmax) and the dissociation constant (Kd), were obtained by means of the Scatchard analysis. The results showed that, while Bmax values did not change in both groups, the Kd values decreased significantly at t1 only in those subjects who bathed in ozonized water. The results of this study, while showing a decrease of the dissociation constant (Kd) which is the inverse of affinity constant, of (3)H-Par binding to SERT in all subjects after balneotherapy and not in those bathing in normal water, suggest that SERT modifications may be related to a specific effect of ozonized water and, perhaps, also to the increased sense of well-being.