The involvement of nitric oxide in the anticonvulsant effects of α-tocopherol on penicillin-induced epileptiform activity in rats

The effects of regular swimming exercise during sodium valproate treatment on seizure behaviors and EEG recordings in pentylenetetrazole-kindled rats

We investigated the effects of alone/combined regular swimming exercise and sodium valproate on epileptic seizure behaviors and EEG recordings, anti-oxidative mechanism, learning, and memory in pentylenetetrazole (PTZ)-kindled rats. Forty-eight healthy rats were randomly divided into eight equal groups as control (CONT), swimming exercise (EX), sodium valproate (SV), SV+EX, PTZ, EX+PTZ, SV+PTZ and SV+EX+PTZ. The rats were forced to regular swimming exercise for 60 min every other day, 13 doses of PTZ (40 mg/kg) were given to induce epileptic seizures and 200 mg/kg SV was given for 28 days. Epileptic seizures were evaluated by visual observation and EEG recordings (total spike numbers and number of epileptiform discharges). Memory and learning skills were assessed with passive avoidance test. According to our visual seizure observations, seizure latency was prolonged only in SV+EX+PTZ (p < 0.001) group, seizure severity score decreased in SV+PTZ (p < 0.05) and SV+EX+PTZ (p < 0.001) groups and seizure frequency was reduced in SV+PTZ (p < 0,001), EX+PTZ (p < 0,001), and SV+EX+PTZ (p < 0,001) groups. Total spike numbers and number of epileptiform discharges highly increased in PTZ group, whereas they decreased in swimming exercise and/or SV treatment groups. The most effective result was seen in the combined therapy group. Memory deficit was observed in PTZ -kindling group, but it didn't change with exercise or SV. Based on our results, regular swimming exercise had positive effects on PTZ-induced seizure frequency, and combined therapy of regular swimming exercise and SV is the most effective way to ameliorate visual seizure behaviors and decrease spike numbers and number of epileptiform discharges according to EEG recordings. Regular swimming exercise could be an alternative option to reduce the dose of SV and the side effects of SV can be avoided in clinical aspects.

Long-term monotherapy treatment with vitamin E reduces oxidative stress, but not seizure frequency in rats submitted to the pilocarpine model of epilepsy

The imbalance between antioxidant system and reactive oxygen species (ROS) generation is related to epileptogenesis, neuronal death, and seizure frequency. Treatment with vitamin E has been associated with neuroprotection and control of seizures. In most experimental studies, vitamin E treatment has short duration. Therefore, the aim of this study was to verify the role of long-term treatment with vitamin E in rats submitted to the pilocarpine model of epilepsy. Rats were divided into two main groups: control (Ctr) and pilocarpine (Pilo). Each one was subdivided according to treatment: vehicle (Ctr V and Pilo V) or vitamin E at dosages of 6 IU/kg/day (Ctr E6 and Pilo E6) or 60 IU/kg/day (Ctr E60 and Pilo E60). Treatment lasted 120 days from status epilepticus (SE). There were no statistical differences concerning treatment in the Ctr group for all variables, so the data were grouped. Carbonyl content in the hippocampus of Pilo V and Pilo E6 was higher compared with that of the Ctr group (8 ± 1.5, 7.1 ± 1, and 3.1 ± 0.3 nmol carbonyl/mg protein, respectively for Pilo V, Pilo E6, and Ctr; p < 0.05). Carbonyl content was restored to control values in Pilo E60 rats (4.2 ± 1.1 and 3.1 ± 0.3 nmol carbonyl/mg protein, respectively for Pilo E60 and Ctr; p > 0.05). The volume of the hippocampal formation (6.5 ± 0.3, 6.6 ± 0.4, 6.3 ± 0.3, and 7.4 ± 0.2, respectively for Pilo V, Pilo E6, Pilo E60, and Ctr) and subfields CA1 (1.6 ± 0.1, 1.4 ± 0.2, 1.5 ± 0.1, and 2 ± 0.05, respectively for Pilo V, Pilo E6, Pilo E60, and Ctr) and CA3 (1.7 ± 0.1, 1.5 ± 0.2, 1.4 ± 0.1, and 2 ± 0.1, respectively for Pilo V, Pilo E6, Pilo E60, and Ctr) was reduced in the Pilo group regardless of treatment. Parvalbumin immunostaining was increased in the hilus of the Pilo E60 group compared with that in the Ctr group (26 ± 2 and 39.6 ± 8.3 neurons, respectively for Ctr and Pilo E60). No difference was found in seizure frequency and Neo-Timm staining. Therefore, long-term treatment with 60 IU/kg/day of vitamin E prevented oxidative damage in the hippocampus and increased hilar parvalbumin expression in rats with epilepsy without a reduction in seizure frequency.

Leptin: role over central nervous system in epilepsy

Adipose tissue is a dynamic organ with different effects on the body. Many of these effects are mediated by leptin, a hormone strongly involved in regulation of feeding and energy metabolism. It has an important role as a mediator of neuronal excitatory activity and higher brain functions. The aim of this study was to review the association between leptin and cerebral neuronal function, in particular its anticonvulsant or convulsant effects and the possible therapeutic role for treating epilepsy. For this purpose, the databases Pubmed, Science Direct, Elsevier, ResearchGate and Scielo were searched to identify experimental studies, reviews and systematic review articles, published in English, Spanish or Portuguese. Experimental studies and the presence of leptin receptors in nervous system sites other than the hypothalamus suggest an influence on higher brain functions. Indeed several animal studies have demonstrated a role of these channels in epileptiform activity as both anticonvulsive and convulsive effects have been found. The reason for these discrepancies is unclear but provides clear evidence of a potential role of leptin and leptin therapy in epileptiform activity. The association between leptin and brain function demonstrates the importance of peripheral metabolic hormones on central nervous system and opens a new way for the development of novel therapeutic interventions in diseases like epilepsy. Nevertheless further investigations are important to clarify the dynamics and diverse actions of leptin on excitatory regulation in the brain.

Antioxidants as a preventive treatment for epileptic process: a review of the current status

Epilepsy is known as one of the most frequent neurological diseases, characterized by an enduring predisposition to generate epileptic seizures. Oxidative stress is believed to directly participate in pathways leading to neurodegeneration, which serves as the most important propagating factor, leading to the epileptic condition and cognitive decline. Moreover, there is also a growing body of evidence showing the disturbance of antioxidant system balance and consequently increased production of reactive species in patients with epilepsy. A meta-analysis, conducted in the present review confirms an association between epilepsy and increased lipid peroxidation. Furthermore, it was also shown that some of the antiepileptic drugs could potentially be responsible for additionally increased lipid peroxidation. Therefore, it is reasonable to propose that during the epileptic process neuroprotective treatment with antioxidants could lead to less sever structural damages, reduced epileptogenesis and milder cognitive deterioration. To evaluate this hypothesis studies investigating the neuroprotective therapeutic potential of various antioxidants in cells, animal seizure models and patients with epilepsy have been reviewed. Numerous beneficial effects of antioxidants on oxidative stress markers and in some cases also neuroprotective effects were observed in animal seizure models. However, despite these encouraging results, till now only a few antioxidants have been further applied to patients with epilepsy as an add-on therapy. Based on the several positive findings in animal models, a strong need for more carefully planned, randomized, double-blind, cross-over, placebo-controlled clinical trials for the evaluation of antioxidants efficacy in patients with epilepsy is warranted.

Homocysteine thiolactone-induced seizures in adult rats are aggravated by inhibition of inducible nitric oxide synthase

Homocysteine and its metabolites (homocysteine thiolactone (HT)) induce seizures via different but still not well-known mechanisms. The role of nitric oxide (NO) in epileptogenesis is highly contradictory and depends on, among other factors, the source of NO production. The aim of the present study was to examine the effects of aminoguanidine, selective inhibitor of inducible NO synthase (iNOS), on HT-induced seizures. Aminoguanidine (50, 75, and 100 mg/kg, intraperitoneally (i.p.)) was injected to rats 30 min prior to inducing HT (5.5 mmol/kg, i.p.). Seizure behavior was assessed by seizure incidence, latency time to first seizure onset, number of seizure episodes, and their severity during observational period of 90 min. Number and duration of spike and wave discharges (SWDs) were determined in electroencephalogram (EEG). Seizure latency time was significantly shortened, while seizure incidence, number, and duration of HT-induced SWD in EEG significantly increased in rats receiving aminoguanidine 100 mg/kg before subconvulsive dose of HT. Aminoguanidine in a dose-dependent manner also significantly increased the number of seizure episodes induced by HT and their severity. It could be concluded that iNOS inhibitor (aminoguanidine) markedly aggravates behavioral and EEG manifestations of HT-induced seizures in rats, showing functional involvement of iNOS in homocysteine convulsive mechanisms.

Inhibitory action of antioxidants (ascorbic acid or α-tocopherol) on seizures and brain damage induced by pilocarpine in rats

Temporal lobe epilepsy is the most common form of epilepsy in humans. Oxidative stress is a mechanism of cell death induced by seizures. Antioxidant compounds have neuroprotective effects due to their ability to inhibit free radical production. The objectives of this work were to comparatively study the inhibitory action of antioxidants (ascorbic acid or α-tocopherol) on behavioral changes and brain damage induced by high doses of pilocarpine, aiming to further clarify the mechanism of action of these antioxidant compounds. In order to determinate neuroprotective effects, we studied the effects of ascorbic acid (250 or 500 mg/kg, i.p.) and α-tocopherol (200 or 400 mg/kg, i.p.) on the behavior and brain lesions observed after seizures induced by pilocarpine (400 mg/kg, i.p., P400 model) in rats. Ascorbic acid or α-tocopherol injections prior to pilocarpine suppressed behavioral seizure episodes. These findings suggested that free radicals can be produced during brain damage induced by seizures. In the P400 model, ascorbic acid and α-tocopherol significantly decreased cerebral damage percentage. Antioxidant compounds can exert neuroprotective effects associated with inhibition of free radical production. These results highlighted the promising therapeutic potential of ascorbic acid and α-tocopherol in treatments for neurodegenerative diseases.

Interaction of leptin and nitric oxide pathway on penicillin-induced epileptiform activity in rats

The aim of the present study was to investigate the role of NO as a mediator of leptin action at the penicillin-induced epileptiform activity in rat. Thirty minutes after penicillin injection, leptin, at a dose of 1 microg, significantly increased the mean frequency of epileptiform activity without changing the amplitude. The effects of systemic administration of nitric oxide synthase (NOS) inhibitors, non-selective NG-nitro-L-arginine methyl ester (L-NAME), selective neuronal NOS inhibitor, 7-nitroindazole (7-NI) and NO precursor, L-arginine on the effects of leptin were investigated. The occurrence of anticonvulsant activity of 7-NI (40 mg/kg, i.p.) was significantly delayed in the presence of leptin (1 microg). The administration of L-NAME (60 mg/kg, i.p.), 30 min before leptin (1 microg) application, did not influence proconvulsant activity of leptin. The administration of L-arginine (1000 mg/kg, i.p.) 30 min before the effective dose of leptin (1 microg, i.c.v.) reversed the proconvulsant effects of leptin whereas the same dose of its inactive enantiomer, D-arginine (1000 mg/kg, i.p.) failed to influence the proconvulsant effect of leptin. The electrophysiological evidence of the present study suggests that neuronal NOS/NO pathway is involved in mediating leptin effects on penicillin-induced epileptiform activity.

Endothelial nitric oxide synthase activity involves in the protective effect of ascorbic acid against penicillin-induced epileptiform activity

Ascorbic acid and nitric oxide are known to play important roles in epilepsy. The aim of present study was to identify the involvement of nitric oxide (NO) in the anticonvulsant effects of ascorbic acid on penicillin-induced epileptiform activity in rats. Intracortical injection of penicillin (500, International Units (IU)) into the left sensorimotor cortex induced epileptiform activity within 2-5 min. Thirty minutes after penicillin injection, nitric oxide synthase (NOS) inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME, 100mg/kg), neuronal nitric oxide synthase (nNOS) inhibitor 7-nitroindazole (7-NI, 40 mg/kg), NO substrate, l-arginine (500 mg/kg) were administered with the most effective dose of ascorbic acid (100 mg/kg) intraperitoneally (i.p.). The administration of l-arginine significantly decreased the frequency of epileptiform activity while administration of l-NAME did not influence the mean frequency of epileptiform activity. Injection of 7-NI decreased the mean frequency of epileptiform activity but did not influence amplitude. Ascorbic acid decreased both the mean frequency and amplitude of penicillin-induced epileptiform activity in rats. The application of l-NAME partially and temporarily reversed the anticonvulsant effects of ascorbic acid. The results support the hypothesis of neuro-protective role for NO and ascorbic acid. The protective effect of ascorbic acid against epileptiform activity was partially and temporarily reversed by nonspecific nitric oxide synthase inhibitor l-NAME, but not selective neuronal nitric oxide synthase inhibitor 7-NI, indicating that ascorbic acid needs endothelial-NOS/NO route to decrease penicillin-induced epileptiform activity.

The effect of L-arginine and L-NAME on pentylenetetrazole induced seizures in ovariectomized rats, an in vivo study

The role of ovarian hormones and nitric oxide (NO) on seizure and their interaction have been widely investigated. The present study carried out to evaluate the effect of chronic administration of L-arginine (LA) and L-NAME (LN) on pentylenetetrazole (PTZ) induced epilepsy in ovariectomized (OVX) and naïve female rats. Fourty-eight female rats were randomly divided into six groups (n=8) as follows: (1) sham, (2) ovarectomized (OVX), (3) sham-LA, (4) sham-LN, (5) OVX-LA, and (6) OVX-LN. The animals of sham-LA and OVX-LA received daily injection of 500 mg/kg L-arginine (i.p.) during 4 weeks. Sham-LN and OVX-LN were treated by 10 mg/kg L-NAME (i.p.) daily for 4 weeks. The animals of sham and OVX groups received 1 ml/kg saline (i.p.) instead of L-arginine and L-NAME. The latencies to minimal clonic seizures (MCS) and generalized tonic-clonic seizures (GTCS) after intraperitoneal injection of penetylenetetrazole (PTZ, 90 mg/kg) was recorded and compared between groups. A significant increase in the GTCS, but not MCS, latency was seen in OVX rats in comparison with sham-operated animals. Pretreatment of animals with L-NAME resulted in a significant increase in the GTCS and MCS latencies in sham group while no significant effects were seen in OVX rats. On the contrary, while pretreatment with L-arginine had no effects on MCS and GTCS latencies in sham group, a significant decrease in GTCS latency was observed in OVX rats. It is concluded that ovarian sex hormones affect seizure thresholds induced by PTZ and NO has a role on seizures susceptibility following PTZ administration. This NO effect might be differing in the presence or absence of ovarian hormones, but further investigations need to be done.

Effects of penicillin on procaine-elicited bursts of potential in central neuron of snail, Achatina fulica

Effects of penicillin on changes in procaine-elicited bursts of potential (BoP) were studied in a central neuron (RP4) of snail, Achatina fulica Ferussac. Procaine elicited BoP in the RP4 neuron while penicillin elicited depolarization of the neuron. Penicillin decreased the BoP elicited by procaine in a concentration-dependent manner. The effect of penicillin on the procaine-elicited BoP was not altered in the preparations treated with ascorbate or L-NAME (N-nitro-L-arginine methyl ester). However, the inhibitory effect of penicillin on the procaine-elicited BoP was enhanced with a decrease in extracellular sodium ion. Sodium ion was one of the important ions contributing to the action potential of the neuron. Two-electrode voltage-clamp studies revealed that penicillin decreased the fast sodium inward current of the neuron. It is concluded that penicillin inhibited the BoP elicited by procaine and sodium ion altered the effect of penicillin on procaine-elicited BoP.

The role of nitric oxide in the anticonvulsant effects of pyridoxine on penicillin-induced epileptiform activity in rats

The present study was conducted to identify the role of nitric oxide (NO) in the anticonvulsant effects of pyridoxine hydrochloride on penicillin-induced epileptiform activity in rats. A single microinjection of penicillin (500 units) into the left sensorimotor cortex induced epileptiform activity within 2-4 min, progressing to full seizure activity lasting about 3-5h. Thirty minutes after penicillin injection, 20, 40, 80, and 160 mg/kg of pyridoxine hydrochloride was administered intraperitoneally (i.p.). Pyridoxine significantly reduced the frequency of penicillin-induced epileptiform activity. A low dose of pyridoxine (40 mg/kg) was the most effective in reducing both the frequency and amplitude of epileptiform activity. The effect of systemic administration of nitric oxide synthase (NOS) inhibitors, non-selective N(G)-nitro-L-arginine methyl ester (L-NAME), selective neuronal NOS inhibitor, 7-nitroindazole (7-NI) and NO substrate, L-arginine on anticonvulsive effects of pyridoxine was investigated. The administration of L-arginine (500 mg/kg, i.p.) and 7-NI (25 and 50 mg/kg, i.p.) significantly decreased the frequency of epileptiform electrocorticographical (ECoG) activity while administration of L-NAME (60 mg/kg, i.p.) and the inactive form of arginine (D-arginine) did not influence it. The administration of L-NAME (60 mg/kg, i.p.) 15 min before pyridoxine (40 mg/kg i.p.) application reversed the anticonvulsant effects of pyridoxine whereas 7-NI (25 and 50 mg/kg, i.p.) did not influence it. The same dose of its inactive enantiomer N(G)-nitro-D-arginine methyl ester (d-NAME) failed to reverse the anticonvulsant effects of pyridoxine. The administration of L-arginine (500 mg/kg, i.p.) did not affect the frequency of epileptiform ECoG activity in the pyridoxine administered group. L-arginine did not reverse the anticonvulsant effect of 7-NI in the penicillin and pyridoxine administered groups. The results of present study indicate that the inhibitory effect on the anticonvulsant activity of pyridoxine against penicillin-induced epileptiform activity was produced by L-NAME, not by 7-NI, and is probably not related to the decrease of NOS activity in the brain.