As it has been shown that the inducedanalgesia can be attenuated or abolished by simultaneous light exposure (Koziak et al. 2006), care was taken to eliminate light intensity and wavelength as confounders (dark conditions). Four experiments were performed: 1) to study the threshold for attenuation at 30 Hz (n=120 mice in six groups), 2) to study the attenuation/abolishment for 120 Hz (n=120 mice in six groups), 3) to evaluate the attenuation of 10, 60, 100, and 240 Hz (n=60 mice in six groups), and 4) to evaluate if the effect changed if the product of amplitude and frequency remained constant but the amplitude and frequency were varied (n=180 mice in six groups).
120 mice were treated in six groups (each group n=20): i) sham exposure (fiberglass box, no shielding) ii) positive control (0 nT, mu-metal box providing static and EMF field shielding) iii) EMF with 25 nT (shielding plus reintroduced fields) iv) EMF with 50 nT v) EMF with 100 nT vi) EMF with 500 nT
33 cm x 38 cm x 20 cm mu-metal box made of 1.6 mm thick mu-metal with magnetically shielded holes of 2.5 cm diameter at each of the four corners on the top and bottom surface; 2.5 cm high mu-metal cylinders surrounding each hole for shielding of the ambient magnetic field and light; box laminated on the inside with black opaque polyethylene
Setup
four coils in a Merrit-like configuration, spaced 9.7 cm apart, for a total length of 29 cm, placed inside the mu-metal box; coils made of 150 turns of AWG#28 magnetic wire (0.32 mm diameter with a thin enamel insulation) wound on 30 cm x 17.8 cm plastic formers; coils connected in parallel pairs and electrically shielded with conductive silver paint and copper foil; mice placed individually in a 26 cm x 16 cm x 12 cm transparent polycarbonate cage covered by a clear polycarbonate top with ventilation holes; cage inserted into the mu-metal box
60 mice were treated in six groups (each group n=10): i) sham exposure (fiberglass box, no shielding) ii) positive control (0 nT, mu-metal box providing static and EMF field shielding) iii) exposure with 60 Hz, 300 nT (shielding plus reintroduced fields) iv) exposure with 240 Hz, 300 nT v) exposure with 10 Hz, 500 nT vi) exposure with 100 Hz, 500 nT
180 mice were treated in six groups (each group n=30): i) sham exposure (fiberglass box, no shielding) ii) positive control (0 nT, mu-metal box providing static and EMF field shielding) iii) exposure with 50 Hz, 120 nT (shielding plus reintroduced fields) iv) exposure with 100 Hz, 60 nT v) exposure with 25 Hz, 240 nT vi) exposure with 12.5 Hz, 480 nT for groups iii) to vi) the product of frequency and magnetic flux density was kept constant (6000 nT Hz)
