Melatonin and petit-mal epilepsy: an hypothesis.

Intraventricular administration of the opioid peptide leucine-enkephalin has been reported to induce petit-mal-like seizures in rats. These seizures have been found to be an age-dependent phenomenon. In rats, the full manifestation of these seizures develops after 4 weeks of age during which time ethosuximide was effective in aborting these seizures, while phenytoin and phenobarbital were ineffective. The period associated with the development of enkephalin-induced seizures in rats coincides with an important milestone in pineal chronobiology. In rats, melatonin plasma levels peak at 3 weeks of age, a period which also corresponds with the emergence of melatonin circadian rhythms. It is proposed that melatonin mediates the anticonvulsant action of drugs effective for petit-mal (absence) epilepsy and that the pineal gland is implicated in the pathogenesis of this form of childhood epilepsy.