Novel anticonvulsant action of chronic melatonin in gerbils

MELATONIN, a hormone from the pineal gland, was tested for its anticonvulsant effects in male gerbils. Daily administration of melatonin (25 μg injection, s.c.) for ten weeks reduced the number and severity of seizures (total convulsion score7.67 ± 1.83 in controls vs 2.47 ± 0.90 in melatonin-injected animals, p < 0.05) associated with the injection of the convulsant, pentylenetetrazol (PTZ, 60 mg kg, s.c.). However, neither 12 weeks of short photoperiod exposure (LD 10:14) nor biweekly administration of melatonin pellets altered PTZ-induced convulsions. Overall, melatonin-injected gerbils were better able to survive and respond to seizures than control animals. No melatonin-injected gerbils died during seizure induction (0/31) while 5 out of 33 control gerbils died after PTZ injection. The mechanism for melatoninʼs anticonvulsant effects could be due to a direct inhibitory action on neural activity or a conversion of melatonin to an anticonvulsant compound that resembles the kynurenines.