Interaction of serotonin and melatonin with sodium, potassium, calcium, lithium and aluminium

In the present study, we investigated the ability of serotonin and melatoni n to bind metals that occur naturally in the brain. An electrochemical tech nique called adsorptive cathodic stripping voltammetry (AdCSV) was employed to study the metal-serotonin or metal-melatonin interactions. The results show that both serotonin and melatonin form stable complexes with lithium a nd potassium, with serotonin favouring lithium over potassium, and melatoni n favouring potassium over lithium. Coordination between either serotonin o r melatonin and calcium was not favoured. The stability of the complexes fo rmed between serotonin and the metals decreased with the metals as follows: Li+ > K+ > Al3+ > Na+ > Ca2+. The trend for melatonin-metal complexes was K+ > Li+ > Na+ > Al3+ > Ca2+. The binding and stable complex formation betw een both ligands, serotonin and melatonin with lithium, potassium and sodiu m is of biological importance. The binding of serotonin to lithium could pr ovide an explanation for the therapeutic effects of lithium in depression t reatment, whereas the binding of aluminium by melatonin could provide insig ht into the role of this element in the aetiology of Alzheimer's disease.