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.
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.