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, 100 mg/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 effects of ethanol intake and withdrawal on penicillin-induced epileptiform activity in rats

Previous experiments have shown that ethanol may have either pro-convulsive or anti-convulsive effects on epileptic activity in different experimental epilepsy models. In this study, the effect of low dose ethanol and its withdrawal on penicillin-induced epileptiform activity in rat was investigated. Eight groups of adult, male Wistar rats were studied: (1) control, (2) penicillin pretreated (500 units), (3) alpha-tocopherol (500 mg/kg, i.m.), (4) penicillin pretreated+alpha-tocopherol, (5) ethanol-treated (3g/kg, per day, for 15 days, intragastrically)+penicillin, (6) ethanol-treated+penicillin+alpha-tocopherol, (7) ethanol withdrawal+penicillin, (8) ethanol withdrawal+penicillin+alpha-tocopherol. Each animal group was composed of seven rats. The epileptiform activity was verified by electrocorticographic (ECoG) recordings. The epileptiform activity was induced by microinjection of penicillin into the left sensorimotor cortex. Administration of ethanol (3g/kg, per day, for 15 days, intragastrically) did not change either frequency or amplitude of penicillin-induced epileptiform activity. The frequency and amplitude of epileptiform activity were evaluated 40 h after the last ethanol administration in withdrawal groups. There was no significant change in the mean frequency and amplitude of epileptiform activity compared with penicillin pretreated and ethanol-treated groups. The effective dose of alpha-tocopherol (500 mg/kg, i.m.) significantly decreased the mean frequency of epileptiform activity in the 60, 70, and 120 min after alpha-tocopherol injection in penicillin pretreated, ethanol-treated, ethanol withdrawal groups, respectively. However, alpha-tocopherol did not affect the amplitude of epileptiform activity in all groups. In conclusion, the present results indicate that low dose of ethanol does not have either anticonvulsive or proconvulsive effect on penicillin-induced epileptiform activity. alpha-Tocopherol has anti-convulsive effect on penicillin-induced epileptiform activity in effective dose.     

The influence of ethanol intake and its withdrawal on the anticonvulsant effect of alpha-tocopherol in the penicillin-induced epileptiform activity in rats

Previous studies proposed the existence of a relationship between epilepsy and ethanol. Ethanol may have either proconvulsive or anticonvulsive effects on epileptic activity in different experimental epilepsy models. The influence of high dose ethanol intake and its withdrawal on the anticonvulsant effect of alpha-tocopherol was examined after intracortical injection of penicillin (500 units) to induce epileptiform activity. Thirty minutes after penicillin injection, the most effective dose of alpha-tocopherol (500 mg/kg) was administrated intramuscularly (i.m.). Ethanol-treated rats received a daily dose of 9.0 g/kg of 30% ethanol solution via an oesophageal probe for 15 days. All rats in the withdrawal group were anesthetized for induction of penicillin-induced epileptiform activity 28 h after the last ethanol administration. The epileptiform activity was verified by electrocorticographic (ECoG) recordings. Ethanol, in a dose of 9 g/kg, significantly decreased the mean frequency of penicillin-induced epileptiform ECoG activity without changing the amplitude. The mean frequency of ECoG activity was decreased in the 60 and 70 min period from penicillin injection in the ethanol-treated+alpha-tocopherol and ethanol withdrawal+alpha-tocopherol groups compared with the penicillin-injected (500 units, i.c.) group, respectively. alpha-Tocopherol was more effective in decreasing the mean frequency of epileptiform activity in the ethanol+alpha-tocopherol group than in other alpha-tocopherol administrated groups. Ethanol withdrawal caused an increase in frequency of epileptiform activity in the withdrawal+alpha-tocopherol group compared with other alpha-tocopherol administrated groups. alpha-Tocopherol did not affect the amplitude of epileptiform activity in any group. Possible mechanisms of ethanol influence on the neuroprotective actions of alpha-tocopherol are still a crucial issue associated with epilepsy.     

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

A variety of animal seizure models exist which help to document the effects of alpha-tocopherol (Vitamin E) and specify its action. In the present study, we provide further evidence for the functional involvement of NO in the anticonvulsant effects of alpha-tocopherol on penicillin-induced epileptiform electrocorticographical (ECoG) activity in rats. The epileptiform ECoG activity was induced by microinjection of penicillin into the left sensorimotor cortex. Thirty minutes after penicillin injection, the most effective dose of alpha-tocopherol (500 mg/kg) was administrated intramuscularly (i.m.). Alpha-tocopherol decreased the frequency of penicillin-induced epileptiform ECoG activity without changing the amplitude. The effect of systemic administration of nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) and NO substrates, L-arginine and sodium nitro prusside (SNP) on anticonvulsive effects of alpha-tocopherol was investigated. The administration of L-NAME (60 mg/kg, i.p.) did not influence the frequency of epileptiform ECoG activity while administration of L-arginine (500 mg/kg, i.p.) and SNP (6 mg/kg, i.p.) significantly decreased in the penicillin-treated group. The administration of L-NAME (60 mg/kg, i.p.) 10 min after alpha-tocopherol (500 mg/kg, i.m.) application reversed the anticonvulsant effects of alpha-tocopherol. The administration of L-arginine (500 mg/kg, i.p.) and SNP (6 mg/kg, i.p.) did not affect the frequency of epileptiform ECoG activity in alpha-tocopherol supplemented group. L-arginine and SNP did not provide an additional anticonvulsant effect in alpha-tocopherol supplemented group. These results support the involvement of the nitric oxide pathway in the anticonvulsant effect of alpha-tocopherol on the penicillin-induced epileptiform ECoG activity.     

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.     

The effect of co-administration of the NMDA blocker with agonist and antagonist of CB1-receptor on penicillin-induced epileptiform activity in rats

Although the activation of CB1-receptor by cannabinoids and block of NMDA receptors are known to decrease seizure severity in epilepsy models, the interaction between these systems remain elusive. Therefore, the present study was initiated to evaluate the possible interactions between cannabinoid compounds and NMDA receptor antagonist in the penicillin-induced epileptiform activity in rat. In the first set of experiments, 30 min after intracortical injection of penicillin, five different doses of memantine (3,5-dimethyl-1-adamantanamine hydrochloride, 1, 2.5, 5, 10 or 20mg/kg) were administered intraperitoneally (i.p.). In the second set of experiments, intracerebroventricular (i.c.v.) AM-251 [N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide], (0.25 μg) a CB1-receptor antagonist and ACEA (arachidonyl-2-chloroethylamide), (7.5 μg) a CB1-receptor agonist, were administered 15 min after memantine (i.p.) application. Memantine, NMDA receptor antagonist, at doses of 2.5 and 5mg/kg (i.p.) decreased the mean frequency of penicillin-induced epileptiform activity with a maximal effect at 5mg/kg. Memantine, at the lowest dose (1mg/kg, i.p.) and highest doses (10 and 20mg/kg, i.p.) did not change the frequency of epileptiform activity. ACEA, at a dose of 7.5 μg, also decreased the frequency of epileptiform activity, whereas AM-251, at a dose of 0.25 μg increased the frequency by causing status epilepticus-like activity. The best and earlier anti-epileptiform effects appeared in both the presence of memantine (5mg/kg, i.p.) and ACEA (7.5 μg, i.c.v.), which was blocked by CB1-receptor antagonist, AM-251. The results of the present study provide electrophysiologic evidence for an interaction between cannabinoid system and NMDA receptors, probably via NMDA-mediated Ca(2+) influx in the penicillin-induced epilepsy.     

The effect of leptin on penicillin-induced epileptiform activity in rats

Leptin is an adipose tissue-derived peptide hormone, which acts as a satiety factor to reduce appetite by interactions with hypothalamic neurons. The other possible physiological functions of leptin are still unclear. In this study, we have evaluated dose-dependent effect of leptin on penicillin-induced epileptiform activity, analyzed by electrocorticogram (ECoG). The epileptiform activity was induced by microinjection of penicillin into the left sensorymotor cortex. Thirty minutes after penicillin injection, 1, 2 or 10 microg of leptin was administrated intracerebroventricularly (i.c.v.). Leptin (1, 2 or 10 microg) alone did not significantly change the spike amplitudes in non-penicillin pretreated control animals. One or two micrograms of leptin significantly increased the frequency of epileptiform activity in the penicillin-pretreated animals. The high dose of leptin (10 microg) did not significantly change either amplitude or frequency of epileptiform activity. One microgram i.c.v. leptin was the most effective dose in changing of frequency on penicillin-induced epileptiform activity. The proconvulsant effects of leptin appeared 90 min after leptin (1 and 2 microg) injection. These data indicate that leptin increases the frequency of penicillin-induced epileptic activity. We speculate that this action of leptin might suggest that leptin may be a proconvulsant substance.     

The effect of serotonin on penicillin-induced epileptiform activity

Objective: This study was aimed at examining the epileptiform activity of the 5-HT₂ serotonin receptor agonist and antagonist, and 5-hydroxytryptophan (5-HTP) in penicillin-induced epilepsy in albino Wistar rats.

Methods: For this purpose, 90 albino male Wistar rats were used in this study. Epileptiform activity was induced by an injection of penicillin, an agonist of GABAA receptor, (500?IU, i.c.) into the somatomotor cortex. Thirty minutes after the injection of penicillin, 2,5-dimethoxy-4-iodoamphetamine (DOI, an agonist of 5-HT₂ receptor) (0.5, 1, 2 and 4?mg/kg, i.p.), methysergide, an antagonist of 5-HT₂ receptor, (1, 10, 20, 50 and 100?µM, i.c.v.) and 5-HTP, precursor of 5-HT, (25, 50, 75 and 100?mg/kg, i.p.) were administered, respectively.

Results: DOI, at the doses of 1 and 2?mg/kg, significantly decreased penicillin-induced epileptiform activity (p?<?0.05). Methysergide, at the doses of 20, 50 and 100?µM, significantly increased the mean spike frequency of penicillin-induced epileptiform activity (p?<?0.05). The doses of 50, 75 and 100?mg/kg of 5-HTP decreased the mean spike frequency of penicillin-induced epileptiform activity (p?<?0.05). The mean of amplitude of penicillin-induced epileptiform activity did not significantly change in any of the groups (p?>?0.05).

Conclusion: The electrophysiological data from the present study suggest that serotonin 5-HT₂ receptors have an important role in controlling penicillin-induced epileptiform activity in the rat.     

The effect of duloxetine on penicillin-induced epileptiform activity in rats

ABSTRACT

Aim: Previous studies showed the existence of a relationship between epilepsy and depression. Duloxetine is a potent and selective inhibitor of serotonin and norepinephrine reuptake (SNRI) used in the treatment of the major depressive disorder. The aim of the present study was to investigate the effect of duloxetine on penicillin-induced epileptiform activity in an experimental rat model of acute partial epilepsy.

Method: In this study, 35 male rats weighing 200–240 g were used. Under urethane anesthesia, tripolar electrodes were placed for electrocorticography (ECoG) recording. Duloxetine, at 1, 5, 10 or 30 mg/kg rates, was administered intraperitoneally 30 minutes after intracortical penicillin (500 IU) injection.

Results: Duloxetine administrations of 1, 5, 10 and 30 mg/kg increased the mean frequency of epileptiform activity 10 minutes after Duloxetine injection compared to the control group (p < 0.05) without changing amplitude in all groups (p > 0.05).

Conclusion: The results showed proconvulsant effect of duloxetine in penicillin-induced epileptiform activity and indicated that it could pose complications risk for people with partial epilepsy.     

Penicillin induced epileptiform activity and EEG spectrum analysis of BDNF heterozygous mice: an in vivo electrophysiological study

Brain-derived neurotrophic factor (BDNF) heterozygous mice (BDNF (+/-)) kindle slowly and have a higher seizure threshold. However, BDNF (+/-) mice exhibit reduced cortical inhibition and disrupted balance of excitation/inhibition synaptic transmission. We investigated penicillin-induced focal cortical epileptiform activity and electroencephalogram (EEG) spectral power of BDNF (+/-) mice, by using electrocorticogram (ECoG) recordings. BDNF (+/-) mice (n=10) and wild type littermates (n=9) were anesthetized with i.p. urethane (1.750g/kg). The recordings of ECoG were carried out by using a data acquisition system and 100IU penicillin was administered intracortically to induce epileptiform activity. The latencies for the onset of spikes and the amplitude of the spikes showed no differences. However the frequency of the spikes was significantly lower in BDNF (+/-) mice at 40th and 45th min following penicillin injection. Additionally, the EEG power for both BDNF (+/-) and wild type mice reduced after penicillin injection and enhanced during epileptiform activity. The spectral power analysis also revealed that the absolute Gamma power of BDNF (+/-) was significantly smaller than wild types. The results of the present study provide the first in vivo electrophysiological evidence that BDNF heterozygous mice exhibited suppressed epileptiform activity. Moreover, reduced levels of BDNF led to a reduction of absolute Gamma band power.