The authors removed pineal glands from euthanized hamsters. The glands were exposed for 7 hours to a 1800 MHz continuous wave (CW) or pulsed GSM electromagnetic field at SARs of 8, 80, 800, and 2700 mW/kg. The glands were perfused during the experiment with a buffer solution. Perfusion samples were collected every hour, and melatonin concentrations were measured by a specific immunoassay.

Both types of signal significantly enhanced melatonin release at 800 mW/kg SAR. At 2700 mW/kg SAR melatonin levels were elevated in the CW, but suppressed in the pulsed GSM group. However, at 2700 mW/kg SAR there was a 1.2°C rise in the experimental system, which supports a thermal explanation for the effects at this level.