MAGNETIC-FIELDS AT RESONANT CONDITIONS FOR THE HYDROGEN-ION AFFECT NEURITE OUTGROWTH IN PC-12 CELLS - A TEST OF THE ION PARAMETRIC RESONANCE MODEL

PC-12 cells primed with nerve growth factor (NGF) were exposed to sinu soidal extremely-low-frequency (ELF) magnetic fields (MFs) selected to test the predictions of the ion parametric resonance (IPR) model unde r resonance conditions fora single ion (hydrogen). We examined the fie ld effects on the neurite outgrowth (NO) induced by NGF using three di fferent combinations of flux densities of the parallel components of t he AC MF (B-ac) and the static MF (B-dc). The first test examined the NO response in cells exposed to 45 Hz at a B-dc of 2.96 mu T with reso nant conditions for H+ according to the model. The B-ac values ranged from 0.29 to 4.11 mu T root-mean-square (rms). In the second test, the MF effects at off-resonance conditions (i.e., no biologically signifi cant ion at resonance) were examined using the frequency of 45 Hz with a B-dc of 1.97 mu T and covering a B-ac range between 0.79 and 2.05 m u T rms. In the third test, the AC frequency was changed to 30 Hz with the subsequent change in B-dc to 1.97 mu T to tune for H+ as in the f irst test. The B-ac values ranged from 0.79 to 2.05 mu T rms. After a 23 h incubation and exposure to the MF in the presence of NGF (5 ng/ml ), the NO was analyzed using a stereoscopic microscope. The results sh owed that the NGF stimulation of neurite ourgrowth (NSNO) was affected by MF combinations over most of the B-ac exposure range generally con sistent with the predictions of the IPR model. However, for a distinct range of B-ac where the IPR model predicted maximal ionic influence, the observed pattern of NSNO contrasted sharply with those predictions . The symmetry of this response suggests that values of B-ac within th is distinct range may trigger alternate or additional cellular mechani sms that lead to an apparent lack of response to the MF stimulus. (C) 1996 Wiley-Liss, lnc.