Objective: To examine the effects of melatonin on the dynamic changes in the concentration of intracellular free Ca2+ ([Ca2+]i) in single intact cultured cortical neurons isolated from fetal rats, in order to explore the possible antiaging mechanisms of melatonin (MT).
Methods: Using the highly fluorescent Ca(2+)-sensitive indicator Fluo-3/AM, cortical neurons cultured in a 35 mm Tissue Culture Dish were in incubated for 45 min at room temperature with 5 mumol/L Fluo-3/AM, resulting in proper intracellular dye concentration to provide adequate signal strength for detection and excellent Laser Scanning Confocal Microscopy (LSCM) imaging of [Ca2+]i while not disturbing normal intracellular physiology. The changes in fluorescent intensity were monitored by LSCM.
Results: Bay K8644 (10(-6) mol/L), KCl (20 mmol/L), sodium L-glutamate (Glu, 50 mumol/L) caused a rapid increase of [Ca2+]i in cortical neurons, and this increase could be significantly attenuated by 10(-6) and 10(-7) mol/L MT.
Conclusions: MT could antagonize the extracellular Ca2+ influx, reduce Ca2+ overload, and have a protective effect on neurons. This may be one of the important antiaging mechanisms of MT.