Involvement of nitric oxide pathway in the acute anticonvulsant effect of melatonin in mice.
Melatonin, the major hormone produced by the pineal gland, is shown to have anticonvulsant effects. Nitric oxide (NO) is a known mediator in seizure susceptibility modulation. In the present study, the involvement of NO pathway in the anticonvulsant effect of melatonin in pentylenetetrazole (PTZ)-induced clonic seizures was investigated in mice. Acute intraperitoneal administration of melatonin (40 and 80 mg/kg) significantly increased the clonic seizure threshold induced by intravenous administration of PTZ. This effect was observed as soon as 1 min after injection and lasted for 30 min with a peak effect at 3 min after melatonin administration. Combination of per se non-effective doses of melatonin (10 and 20 mg/kg) and nitric oxide synthase (NOS) substrate L-arginine (30, 60 mg/kg) showed a significant anticonvulsant activity. This effect was reversed by NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg), implying an NO-dependent mechanism for melatonin effect. Pretreatment with L-NAME (30 mg/kg) and N(G)-nitro-L-arginine (L-NNA, 10 mg/kg) inhibited the anticonvulsant property of melatonin (40 and 80 mg/kg) and melatonin 40 mg/kg, respectively. Specific inducible NOS (iNOS) inhibitor aminoguanidine (100 and 300 mg/kg) did not affect the anticonvulsant effect of melatonin, excluding the role of iNOS in this phenomenon, while pretreatment of with 7-NI (50 mg/kg), a preferential neuronal NOS inhibitor, reversed this effect. The present data show an anticonvulsant effect for melatonin in i.v. PTZ seizure paradigm, which may be mediated via NO/L-arginine pathway by constitutively expressed NOS.
Yahyavi-Firouz-Abadi
Noushin
N
Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.
Tahsili-Fahadan
Pouya
P
Riazi
Kiarash
K
Ghahremani
Mohammad Hossein
MH
Dehpour
Ahmad Reza
AR
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology* / Q000627:therapeutic use; D001120:Arginine / Q000494:pharmacology; D003292:Convulsants; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D007191:Indazoles / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007696:Kindling, Neurologic / Q000187:drug effects*; D008297:Male; D008550:Melatonin / Q000494:pharmacology* / Q000627:therapeutic use; D051379:Mice; D008815:Mice, Inbred Strains; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II / Q000494:pharmacology; D019335:Nitroarginine / Q000494:pharmacology; D010433:Pentylenetetrazole; D012640:Seizures / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology
D000927:Anticonvulsants; D003292:Convulsants; D004791:Enzyme Inhibitors; D006146:Guanidines; D007191:Indazoles; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D008550:Melatonin; C004479:pimagedine; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester; D010433:Pentylenetetrazole