The present study was designed to investigate the involvement of the
nitric oxide (NO)/cyclic guanylate monophosphate pathway in
pilocarpine-induced
seizures in mice. Male Swiss mice (26-32 g) were used as the in vivo model. The following pharmacological tools were utilized: the non-selective
NO synthase (NOS) inhibitor
L-NAME (10 mg/kg, i.p.), a preferential inducible NOS (iNOS) inhibitor
aminoguanidine (25 mg/kg, i.p.), a highly specific iNOS inhibitor 1400W (2.5 mg/kg, i.p.), the NO donor
L-arginine (150 mg/kg, i.p.), and the
soluble guanylyl cyclase inhibitor ODQ (10 mg/kg, i.p.). The animals were divided into groups (n = 8) and pretreated for 30 min before receiving
pilocarpine (400 mg/kg, i.p.), while the control group received only
pilocarpine. They were observed for 60 min to measure initial seizure latency, latency till death, and mortality. An administration of
L-NAME or ODQ delayed the onset of initial seizure, increased latency till death, and produced a 25% survival rate.
Aminoguanidine increased the initial seizure and latency until death, and administration of 1400W did not have an effect. Incremental increases of NO by
L-arginine were capable of decreasing the seizure and death latency. These results support the idea that the constitutive NOS, probably neuronal NOS, followed by
soluble guanylyl cyclase activation is involved in the convulsive responses caused by
pilocarpine administration.