Isolated crawfish mechanoreceptor neuron response to weak extremely low frequency magnetic fields

Responses of single neurons to weak extremely low frequency magnetic fields were studied over the wide ranges of frequencies (from 0.001 to 100 Ilz), and amplitudes (from 1 to 400 mu T). Neuron firing shifts were usually weak and variable: firing frequency increased or decreased slowly. Inhibitory n euron responses were observed more often than excitatory ones. Frequency an d amplitude <<action spectra>>, P(F) and P(B), included several bands: P(F) was maximal at: 0,001; 0,3; 3, and: 60 Hz, and P(B) has maximal at 5; 20; 50 and 300 mu T. Geomagnetic field variations influenced crawfish neuron se nsitivity to extremely low frequency magnetic fields. Dependences P(A(p)) a nd P(K-p) were also nonlinear; P(K-p) was maximal at K-p = 0 and 5-6, and P (A(p)) was maximal at 3; 14, and 18 nT. Neuron sensitivity to extremely fre quency magnetic fields increased almost; monotonically from March to Octobe r showing the dependence on season changes in neuron metabolic state. The p ossible explanation of these data on the base of cyclotron or parametric re sonance theories is discussed.