Medical/biological study (experimental study)

The influences of extremely low frequency magnetic fields on clonidine-induced sleep in 2-day-old chicks med./bio.

By: Min YS, Jeong JH, Choi YM, Lee BC, Huh IH, Lee SY, Sohn UD

Published in: J Auton Pharmacol 2001; 21 (4): 197-203

To investigate whether magnetic fields modulate clonidine-induced sleep in 2-day-old chicks.

Effects of magnetic fields on clonidine-induced sleep might be related to central alpha-adrenergic receptors. Central alpha-adrenergic receptors inhibit presynaptic release of noradrenaline in the CNS.
Two-day-old chicks were given clonidine (selective alpha-adrenergic receptors agonist) and exposed. In addition, to determine whether the GABA/benzodiazepine receptor system is involved in in clonidine-induced sleep, the respective antagonists bicuculline (0.1 mg/kg) or flumazenil (0.5 mg/kg) were injected 10 min before clonidine with or without magnetic field exposure.
Eight to ten chicken were used in each group.

effects on the neurological system: levels of noradrenaline, tyrosine, GABA in the brain
sleep: sleep duration and onset time

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: 3 h, 6 h, 9 h or 12 h	magnetic flux density: 0.54 mT effective value magnetic flux density: 1 mT effective value magnetic flux density: 2 mT effective value

Exposure source	Helmholtz coils
Setup	2 pairs of vertically oriented Helmholtz coils each consisting of 3 coils in a wooden frame

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.54 mT	effective value	measured	-	-
magnetic flux density	1 mT	effective value	measured	-	-
magnetic flux density	2 mT	effective value	measured	-	-

Exposed system:

effects on the neurological system: levels of noradrenaline, tyrosine, GABA in the brain: high performance liquid chromatography with electro-chemical detection
sleep: sleep duration (time interval duration when the chicks lost and regained the righting reflex) and onset time (seconds from the administration of clonidine to the loss of righting reflex)

Investigated system:

Investigated organ system:

Time of investigation:

Clonidine produced a dose-related increase of the sleeping time and a decrease of the onset time. The clonidine-induced sleep time increased with the intensity and duration of the magnetic field exposure. The onset time of clonidine-induced sleep was not altered by magnetic fields.
Clonidine reduced noradrenaline or tyrosine in the brain independent of the magnetic field exposure, confirming that central alpha-adrenergic receptors inhibit presynaptic release of noradrenaline in the CNS.
Bicuculline and flumazenil inhibited the increase of clonidine-induced sleep time by magnetic fields. The onset time was not altered by magnetic fields after pretreatment with bicuculline and flumazenil. Clonidine, magnetic fields or both in combination did not change GABA levels in the brain.
Magnetic fields increase sleep time induced by clonidine. These effects might be related to both the noradrenaline and GABA systems.

Study character:

Akerstedt T et al. (1999): A 50-Hz electromagnetic field impairs sleep
Blackwell RP et al. (1985): Effects of electric field exposure on some indices of CNS arousal in the mouse