Hata K, Yamaguchi Y, Tsurita G, Watanabe S, et al. (2005)

The aim of this study was to investigate the effects on melatonin synthesis in rats after short-term exposure to radiofrequency radiation.

Rats were exposed in a carousel type system, in which eight animals could be exposed at one time. The heads were exposed locally to a 1439 MHz TDMA signal (burst trains of pulses at 50 Hz, 1/3 duty ratio. 6.7 ms pulse width). The average specific absorption (SAR) of the brain was 7.5 W/kg, about four times stronger than that seen in mobile phones.

Four different groups of animals were used, with equal number of males and females in each group. The exposure, sham, and cage control groups each had 64 rats, and the light control 16. All animals were acclimatized to a 12-hour light/12 hour dark cycle for at least 2 weeks. The exposure group was exposed for 4 hours on one day during the dark cycle. Those in the sham group were placed in the exposure system but not exposed to RF radiation. Those in the cage control group were not placed in the exposure system. Those in the light control group were exposed to the light condition until measurement.

The rats were sacrificed either at 90 minutes or at 6 hours after the test period. Blood was extracted and the pineal gland removed. The pineal and serum melatonin levels were measured, as well as the pineal serotonin level. Melatonin is synthesized from melatonin in the pineal gland.

Both the pineal and serum melatonin levels were unchanged at the two time points investigated, except in the light control group, which showed a significant decrease in melatonin levels. The results from the latter group supported the accuracy of measurement. The pineal serotonin level, as expected, increased in the light control group, but it remained unchanged in the other 3 groups.

The authors acknowledge the need for studies that will examine the effect of long term exposure to RF radiation.