Effects of d-penicillamine on pentylenetetrazole-induced seizures in mice: Involvement of nitric oxide/NMDA pathways

Besides the clinical applications of penicillamine, some reports show that use of d-penicillamine (d-pen) has been associated with adverse effects such as seizures. So, the purpose of this study was to evaluate the effects of d-pen on pentylenetetrazole (PTZ)-induced seizures in male NMRI mice. It also examined whether N-methyl-d-aspartate (NMDA) receptor/nitrergic system blockage was able to alter the probable effects of d-pen.Different doses of d-pen (0.1, 0.5, 1, 10, 100, 150, and 250 mg/kg) were administered intraperitoneally (i.p.) 90 min prior to induction of seizures. d-Penicillamine at a low dose (0.5 mg/kg, i.p.) had anticonvulsant effects, whereas at a high dose (250 mg/kg, i.p.), it was proconvulsant. Both anti- and proconvulsant effects of d-pen were blocked by a single dose of a nonspecific inhibitor of nitric oxide synthase (NOS), l-NAME (10 mg/kg, i.p.), and a single dose of a specific inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitroindazole (30 mg/kg, i.p.). A selective inhibitor of iNOS, aminoguanidine (100 mg/kg, i.p.), had no effect on these activities. An NMDA receptor antagonist, MK-801 (0.05 mg/kg, i.p.), alters the anti- and proconvulsant effects of d-pen.The results of the present study showed that the nitric oxide system and NMDA receptors may contribute to the biphasic effects of d-pen, which remain to be clarified further.