Proconvulsant effects of central and peripheral administration of L-name on penicillin-induced epilepsy in rats

The effects of bacterial endotoxin LPS on synaptic transmission at the neuromuscular junction

The direct action of bacterial lipopolysaccharides (LPS) endotoxin was shown to enhance synaptic transmission and hyperpolarize the membrane potential at low doses, but block glutamatergic receptors and decrease observable spontaneous events at a high dosage. The dosage effects are LPS type specific. The hyperpolarization is not due to voltage-gated potassium channels or to activation of nitric oxide synthase (NOS). The effects are induced directly by LPS, independent of an immune response.

Anticonvulsant effects of focal and intracerebroventricular adenosine on penicillin-induced epileptiform activity in rats

Adenosine has potent anticonvulsant effects on various models of experimental epilepsy. In the present study, we examined the effects of focal and intracerebroventricular (i.c.v.) adenosine on penicillin-induced epileptiform activity in Wistar rats. The effects of theophylline, a non-selective adenosine receptor antagonist, were also researched. The recordings of electrocorticogram (ECoG) were carried out by using a data acquisition system, under urethane anesthesia. Adenosine was given in doses of 1, 10 and 100 microg/rat via focal and i.c.v. 30 min after penicillin administration. Theophylline was injected in doses of 1, 10 and 100 microg/rat by i.c.v. too. Adenosine administration significantly decreased the spike frequency while theophylline increased. Focal adenosine is more effective than i.c.v. adenosine. 100 microg adenosine is an effective dose that causes a decrease in epileptiform activity during experiments. We also demonstrated that 100 microg theophylline significantly increased epileptiform activity. Our findings suggest that focal adenosine is more effective than i.c.v. adenosine on epileptiform activity.

Effects of L-arginine on penicillin-induced epileptiform activity in rats

It has been suggested that nitric oxide (NO) is involved in the pathophysiology of epilepsy. Data are, however controversial because it is not clear whether NO has pro- or anticonvulsant effects. The aim of this study was to investigate the effects of NO on penicillin G-induced epileptiform activity. The left cerebral cortex was exposed by craniotomy in urethane-anesthetized Wistar rats. The epileptic activity was produced by intraperitoneal injection of penicillin G (3 million U/kg, i.p.). The ECoG (electrocorticogram) activity was displayed on a four-channel recorder. At 39.7 +/- 5.4 min after penicillin administration, large amplitude sharp waves appeared in the ECoG. Mean spike frequency and mean spike amplitude were calculated as 29.5 +/- 3.2/min and 865 +/- 91 microV, respectively, at the 55th min. 7-Nitroindazole (60 mg/kg, i.p.) injection 30 min before penicillin G administration significantly reduced the latency of epileptiform activity. Intracerebroventricular administration of L-arginine (300 microg/2 microl, i.c.v.) and sodium nitroprusside (100 microg/2 microl, i.c.v.) suppressed epileptiform activity. Saline (2 microl) and D-arginine (300 microg/2 microl, i.c.v.) administration into the cerebral ventricle were completely ineffective on epileptiform activity (P<0.01). These findings suggest that NO may be an endogenous antiepileptic substance.