Stimulation of neurite outgrowth in PC12D cells by ELF magnetic field and suppression by melatonin

Abstract

PC12D cells pertain to the subline of rat pheochromocytoma cells and are differentiated into nerve-like cells by NGF (nerve growth factor) or forskolin. In order to clarify the effect of magnetic fields at extremely low frequency (ELF) on nervous system in vitro, we observed neurite outgrowth in PC12D, which was induced for 22 h culture by 10 μM forskolin in both a pair of Helmholtz coils and a magnetically shielded box. Under the magnetic fields of 33.3 μT in vertical at 60 Hz and of geomagnetism, the neurite factor F was increased 1.3 times greater than that in the shielded box; F=( f− f 0)/( f R− f 0), where f= n +/ n T, n + is the number of neurite-bearing cells for the total number n T of cells ( n T∼180) counted under microscope and the subscripts R and 0 denote f's of cells with 10 μM and no forskolin, respectively. Furthermore we observed the influence of melatonin, since melatonin is expected to protect the electromagnetic damage to living organisms. F decreased at the three concentrations of 0.11, 5.3 and 260 nM melatonin significantly as compared with that at no melatonin under the magnetic fields, although F was not significantly varied under no magnetic fields except that at 260 nM melatonin. It is concluded that ELF magnetic field stimulated neurite outgrowth in PC12D cells induced by forskolin and melatonin suppressed its effect at low concentration corresponding to physiological level of melatonin. It is discussed on the relation between neurite outgrowth and Ca 2+ influx through membrane.