ABSTRACT
PURPOSE: The goal of the present study was to investigate the effect of low magnesium on the excitability of visual cortex, observe the induction of epileptiform activity, and define the characteristics of spontaneous activity. METHODS: We divided 19-23 days-old Sprague-Dawley rats into three groups; they were divided by the concentration of Mg, 1 (n=10), 0.5 (n=13), and 0 (n=14) mM. The visual cortex slices from brain were incubated in artificial CSF for one hour, and then extracellular recordings were performed. RESULTS: The latency of interictal epileptiform activity in 0.5 and 0 mM Mg was 26.9+/-11.7 and 13.3+/-2.7 min, the frequency was 1.1+/-0.7 and 5.7+/-0.7 min-1, the amplitude was 1.0+/-0.3 and 1.4+/-0.4 mV, the duration was 15.1+/-15.4 and 587.4+/-398.0 ms. The latency of ictal epileptiform activity in 0 mM Mg was 15.5+/-8.0 min, the frequency was 53.8+/-16.3 /event, the amplitude was 2.9+/-0.7 mV, the duration was 25.2+/-6.0 s. CONCLUSIONS: Low Mg showed the increased excitability in the visual cortex and induced the interictal and ictal spontaneous epileptiform activity. This induction was abolished by D-AP5 and decreased by CNQX. This result may provide insights into the events underlying the epileptogenesis.
Subject(s)
Animals , Rats , 6-Cyano-7-nitroquinoxaline-2,3-dione , Brain , Magnesium , Rats, Sprague-Dawley , Visual CortexABSTRACT
PURPOSE: The goal of this study was to investigate the effects of bicuculline(BIC) on the excitability of visual cortex, observe the induction of epileptiform activity and define the characteristics of spontaneous activity. METHODS: We divided 19 to 23-day-old Sprague-Dawley rats into 3 groups by the concentration of BIC:5(n=10), 20(n=12), and 40(n=10) microM. The slices from the rats were incubated in artificial CSF for 1 hour, and then extracellular recordings were performed. RESULTS: Spontaneous epileptiform activities were observed in all of the BIC groups. The latencies of 5, 20, and 40 microM BIC were 31.6+/-13.0, 34.0+/-11.9, and 6.3+/-3.2 min. The frequencies of 5, 20, and 40 microM BIC were 1.1+/-0.5, 2.7+/-1.8, and 19.1+/-23.3 min-1. The amplitudes of 5, 20, and 40 microM BIC were 5.4+/-1.4, 6.9+/-0.9, 11.1+/-1.3 mV. The durations of 5, 20, and 40 microM BIC were 444.6+/-169.1, 865.2+/-151.2, and 1,014.7+/-613.8 ms. CONCLUSION: BIC is associated with increased excitability in the visual cortex and induces spontaneous epileptiform activities. This induction was decreased by D-AP5 or CNQX.
Subject(s)
Animals , Rats , 6-Cyano-7-nitroquinoxaline-2,3-dione , Bicuculline , Rats, Sprague-Dawley , Visual CortexABSTRACT
PURPOSE: The goal of the present study was to investigate the effects of 4-aminopyridine(4-AP) on the excitability of visual cortex, observe the induction of epileptiform activity and define the characteristics of spontaneous activity. METHODS: We divided 19 to 23-day-old Sprague-Dawley rats into 3 groups by the concentration of 4-AP:5(n=10), 50(n=11), and 100(n=12) microM. The slices from their brains were incubated in artificial CSF for 1 hour, and then extracellular recordings were performed. RESULTS: Spontaneous epileptiform activities were observed in 50 and 100 microM 4-AP groups. The latencies of interictal epileptiform activity were 7.8+/-1.1 and 5.8+/-0.9 min, the frequencies 1.8+/-0.2 and 24.1+/-6.6 min-1, the amplitudes 0.7+/-0.1 and 2.8+/-0.5 mV, and the durations 238.0+/-57.8 and 242.2+/-70.0 ms in 50 and 100 microM 4-AP groups respectively. The latencies of ictal epileptiform activity were 21.0+/-9.8 and 6.7+/-2.3 min, the frequencies 116.2+/-46.7 and 193.7+/-26.4/event, the amplitudes 3.1+/-0.8 and 2.8+/-0.9 mV, and the durations 26.9+/-27.6, 35.2+/-12.6 s in 50 and 100 microM 4-AP groups respectively. CONCLUSION: 4-AP showed increased excitability in the visual cortex and induced interictal and ictal spontaneous epileptiform activity. This induction was decreased by D- AP5 or CNQX. Those results suggest that both types of inotropic excitatory amino acid receptors are overactivated and contribute to seizure initiation and propagation.
Subject(s)
4-Aminopyridine , 6-Cyano-7-nitroquinoxaline-2,3-dione , Brain , Rats, Sprague-Dawley , Receptors, Glutamate , Seizures , Visual CortexABSTRACT
The effect of GABA ergic system in the brain in mediating convulsions induced by quinolinic acid (QA) was studied. Muscimol,an agonist of GABAA-receptor, and aminooxyacetic acid (AOAA),an inhibitor of GABA transami-nase(GABA-T) ,and alprazolam which increased the affinity of GABA-receptor as it binds with benzodiazepine-receptor, were used to increase GABAergic function in the brain. Results showed that the above substances antagonized QA-induced convulsions. In contrast, bicu-culline,an antagonist of GABAA-receptor, and 3-mercaptopropionic acid (3-MP), an inhibitor of both GABA synthesis and its release, were used to decrease GABA ergic function in the CNS. They were found to potentiate QA-induced seizures. All these results suggest that GABA ergic system in brain plays an important role in modulating QA-induced convulsions.
ABSTRACT
Cis-3, 4-dichloro -a-chloro-cinnamoyl-sec.-butylamine (8601), a new compound of cinnamamides, has potent antagonistic effect on experimental epilepsy. 8601 is significantly more effective against MES in mice than Antiepilepsirine. It has also been found effective against convulsion induced by icv. injection of sodium glu-tamate and zinc sulfate.The mechanisms of anti-MES of 8601 is related to content of 5 HT in the whole brain of mice. Increased cerebral 5 HT with L-tyrosine potentiated the effect of anti-MES of 8601,while the opposite was obtained using reserpine or pCPA which decreased the concentration of cerebral 5 HT. The increase of cerebral 5 HT is correlated with the effect of anti-MES of 8601 with a correlation coefficient of 0.926 ( P