Objective To investigate the effects of 900 MHz microwave radiation on circadian rhythm of locomotor activities and plasma melatonin levels in rats.
Methods Locomotor activities of 30 rats were measured over a 24 h period, and 24 rats fitting phase response curves (PRCs) of circadian rhythm were selected and randomly divided into control, light, ZT3, and ZT15 groups (6 rats for each group). The group ZT3 and group ZT15 were exposed to 40 μW/cm2, 900 MHz microwave radiation at trough time (ZT3) and peak time (ZT15) of PRCs, respectively, 1 h/d for 14 d. The group light was exposed to 300 lx visible light at peak time (ZT15), 1 h/d for 14 d. Blood was collected from heart within 48 h after microwave or light exposure (i.e. the first 24 h:ZT3, ZT11, and ZT19; the second 24 h:ZT7, ZT15, and ZT23). Locomotor activities and plasma melatonin concentrations were analyzed with cosine model.
Results The mesors and amplitudes of locomotor activity curves in group light, group ZT3, and group ZT15 decreased significantly after the exposures (P < 0.05), and the acrophases were delayed (P < 0.05). For group light and group ZT3, the mesors and amplitudes of plasma melatonin concentrations were reduced significantly after the radiation (P < 0.05), and the acrophases were delayed (P < 0.05). Compared with the controls, the amplitude of plasma melatonin concentrations of group ZT15 was lowered obviously after radiation, and the acrophase was delayed (P < 0.05).
Conclusion Exposure to 40 μW/cm2, 900MHz microwave at trough time and peak time can affect the circadian rhythm of locomotor activity and plasma melatonin level in rats.
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