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Anticonvulsant and proconvulsant roles of nitric oxide in experimental epilepsy models
E A Del-Bel1, P R Oliveira, J A Oliveira
1Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, SP, Brasil.
Abstract:
The effect of acute (120 mg/kg) and chronic (25 mg/kg, twice a day, for 4 days) intraperitonial injection of the nitric oxide (NO) synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG) was evaluated on seizure induction by drugs such as pilocarpine and pentylenetetrazole (PTZ) and by sound stimulation of audiogenic seizure-resistant (R) and audiogenic seizure-susceptible (S) rats. Seizures were elicited by a subconvulsant dose of pilocarpine (100 mg/kg) only after NOS inhibition. NOS inhibition also simultaneously potentiated the severity of PTZ-induced limbic seizures (60 mg/kg) and protected against PTZ-induced tonic seizures (80 mg/kg). The audiogenic seizure susceptibility of S or R rats did not change after similar treatments. In conclusion, proconvulsant effects of NOS inhibition are suggested to occur in the pilocarpine model and in the limbic components of PTZ-induced seizures, while an anticonvulsant role is suggested for the tonic seizures induced by higher doses of PTZ, revealing inhibitor-specific interactions with convulsant dose and also confirming the hypothesis that the effects of NOS inhibitors vary with the model of seizure.
Insights
Nitric oxide synthase (NOS) inhibition affects seizure susceptibility differently depending on the drug and seizure type. NOS inhibition promoted pilocarpine seizures but had mixed effects on pentylenetetrazole seizures.
Area of Science:
- Neuroscience
- Pharmacology
- Biochemistry
Background:
- Nitric oxide (NO) plays a complex role in the central nervous system.
- Nitric oxide synthase (NOS) is the enzyme responsible for NO production.
- Understanding NOS inhibition's effect on seizures is crucial for neurological research.
Purpose of the Study:
- To investigate the impact of NG-nitro-L-arginine (L-NOARG), a NOS inhibitor, on seizure induction.
- To determine if NOS inhibition influences seizure susceptibility in different animal models and seizure types.
Main Methods:
- Administered acute and chronic intraperitoneal injections of L-NOARG to rats.
- Induced seizures using pilocarpine, pentylenetetrazole (PTZ), and sound stimulation.
- Evaluated seizure severity and susceptibility in audiogenic seizure-resistant (R) and susceptible (S) rats.
Main Results:
- NOS inhibition elicited seizures with a subconvulsant dose of pilocarpine.
- NOS inhibition potentiated limbic seizures induced by a lower PTZ dose (60 mg/kg) but protected against tonic seizures induced by a higher PTZ dose (80 mg/kg).
- Audiogenic seizure susceptibility in R and S rats remained unchanged after NOS inhibition.
Conclusions:
- NOS inhibition exhibits proconvulsant effects in the pilocarpine model and for limbic seizures induced by PTZ.
- NOS inhibition demonstrates anticonvulsant properties against tonic seizures induced by higher PTZ doses.
- The effects of NOS inhibitors on seizures are model-specific and dose-dependent, highlighting complex interactions within the seizure pathways.