The impact of amygdala glutamate receptors on cardiovascular function in rats with post-traumatic stress disorder / 生理学报

Post-traumatic stress disorder (PTSD) has been reported to be associated with a higher risk of cardiovascular disease. The amygdala may have an important role in regulating cardiovascular function. This study aims to explore the effect of amygdala glutamate receptors (GluRs) on cardiovascular activity in a rat model of PTSD. A compound stress method combining electrical stimulation and single prolonged stress was used to prepare the PTSD model, and the difference of weight gain before and after modeling and the elevated plus maze were used to assess the PTSD model. In addition, the distribution of retrogradely labeled neurons was observed using the FluoroGold (FG) retrograde tracking technique. Western blot was used to analyze the changes of amygdala GluRs content. To further investigate the effects, artificial cerebrospinal fluid (ACSF), non-selective GluR blocker kynurenic acid (KYN) and AMPA receptor blocker CNQX were microinjected into the central nucleus of the amygdala (CeA) in the PTSD rats, respectively. The changes in various indices following the injection were observed using in vivo multi-channel synchronous recording technology. The results indicated that, compared with the control group, the PTSD group exhibited significantly lower weight gain (P < 0.01) and significantly decreased ratio of open arm time (OT%) (P < 0.05). Retrograde labeling of neurons was observed in the CeA after microinjection of 0.5 µL FG in the rostral ventrolateral medulla (RVLM). The content of AMPA receptor in the PTSD group was lower than that in the control group (P < 0.05), while there was no significant differences in RVLM neuron firing frequency and heart rate (P > 0.05) following ACSF injection. However, increases in RVLM neuron firing frequency and heart rate were observed after the injection of KYN or CNQX into the CeA (P < 0.05) in the PTSD group. These findings suggest that AMPA receptors in the amygdala are engaged in the regulation of cardiovascular activity in PTSD rats, possibly by acting on inhibitory pathways.

Korean red ginseng excitation of paraventricular nucleus neurons via non-N-methyl-D-aspartate glutamate receptor activation in mice

It has been reported that Korean red ginseng (KRG), a valuable and important traditional medicine, has varied effects on the central nervous system, suggesting its activities are complicated. The paraventricular nucleus (PVN) neurons of the hypothalamus has a critical role in stress responses and hormone secretions. Although the action mechanisms of KRG on various cells and systems have been reported, the direct membrane effects of KRG on PVN neurons have not been fully described. In this study, the direct membrane effects of KRG on PVN neuronal activity were investigated by using a perforated patch-clamp in ICR mice. In gramicidin perforated patch-clamp mode, KRG extract (KRGE) induced repeatable depolarization followed by hyperpolarization of PVN neurons. The KRGE-induced responses were concentration-dependent and persisted in the presence of tetrodotoxin, a voltage sensitive Na+ channel blocker. The KRGE-induced responses were suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione (10 µM), a non-N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, but not by picrotoxin, a type A gamma-aminobutyric acid receptor antagonist. The results indicate that KRG activates non-NMDA glutamate receptors of PVN neurons in mice, suggesting that KRG may be a candidate for use in regulation of stress responses by controlling autonomic nervous system and hormone secretion.

Botulinum toxin type A enhances the inhibitory spontaneous postsynaptic currents on the substantia gelatinosa neurons of the subnucleus caudalis in immature mice

Botulinum toxin type A (BoNT/A) has been used therapeutically for various conditions including dystonia, cerebral palsy, wrinkle, hyperhidrosis and pain control. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) receive orofacial nociceptive information from primary afferents and transmit the information to higher brain center. Although many studies have shown the analgesic effects of BoNT/A, the effects of BoNT/A at the central nervous system and the action mechanism are not well understood. Therefore, the effects of BoNT/A on the spontaneous postsynaptic currents (sPSCs) in the SG neurons were investigated. In whole cell voltage clamp mode, the frequency of sPSCs was increased in 18 (37.5%) neurons, decreased in 5 (10.4%) neurons and not affected in 25 (52.1%) of 48 neurons tested by BoNT/A (3 nM). Similar proportions of frequency variation of sPSCs were observed in 1 and 10 nM BoNT/A and no significant differences were observed in the relative mean frequencies of sPSCs among 1–10 nM BoNT/A. BoNT/A-induced frequency increase of sPSCs was not affected by pretreated tetrodotoxin (0.5 µM). In addition, the frequency of sIPSCs in the presence of CNQX (10 µM) and AP5 (20 µM) was increased in 10 (53%) neurons, decreased in 1 (5%) neuron and not affected in 8 (42%) of 19 neurons tested by BoNT/A (3 nM). These results demonstrate that BoNT/A increases the frequency of sIPSCs on SG neurons of the Vc at least partly and can provide an evidence for rapid action of BoNT/A at the central nervous system.

Dual control of the vestibulosympathetic reflex following hypotension in rats

Orthostatic hypotension (OH) is associated with symptoms including headache, dizziness, and syncope. The incidence of OH increases with age. Attenuation of the vestibulosympathetic reflex (VSR) is also associated with an increased incidence of OH. In order to understand the pathophysiology of OH, we investigated the physiological characteristics of the VSR in the disorder. We applied sodium nitroprusside (SNP) to conscious rats with sinoaortic denervation in order to induce hypotension. Expression of pERK in the intermediolateral cell column (IMC) of the T4~7 thoracic spinal regions, blood epinephrine levels, and blood pressure were evaluated following the administration of glutamate and/or SNP. SNP-induced hypotension led to increased pERK expression in the medial vestibular nucleus (MVN), rostral ventrolateral medullary nucleus (RVLM) and the IMC, as well as increased blood epinephrine levels. We co-administered either a glutamate receptor agonist or a glutamate receptor antagonist to the MVN or the RVLM. The administration of the glutamate receptor agonists, AMPA or NMDA, to the MVN or RVLM led to elevated blood pressure, increased pERK expression in the IMC, and increased blood epinephrine levels. Administration of the glutamate receptor antagonists, CNQX or MK801, to the MVN or RVLM attenuated the increased pERK expression and blood epinephrine levels caused by SNP-induced hypotension. These results suggest that two components of the pathway which maintains blood pressure are involved in the VSR induced by SNP. These are the neurogenic control of blood pressure via the RVLM and the humoral control of blood pressure via epinephrine release from the adrenal medulla.

Activation of group II metabotropic glutamate receptors blocks zinc release from hippocampal mossy fibers

BACKGROUND: The hippocampal CA3 area contains large amounts of vesicular zinc in the mossy fiber terminals which is released during synaptic activity, depending on presynaptic calcium. Another characteristic of these synapses is the presynaptic localization of high concentrations of group II metabotropic glutamate receptors, specifically activated by DCG-IV. Previous work has shown that DCG-IV affects only mossy fiber-evoked responses but not the signals from associational-commissural afferents, blocking mossy fiber synaptic transmission. Since zinc is released from mossy fibers even for single stimuli and it is generally assumed to be co-released with glutamate, the aim of the work was to investigate the effect of DCG-IV on mossy fiber zinc signals. RESULTS: Studies were performed using the membrane-permeant fluorescent zinc probe TSQ, and indicate that DCG-IV almost completely abolishes mossy fiber zinc changes as it does with synaptic transmission. CONCLUSIONS: Zinc signaling is regulated by the activation of type II metabotropic receptors, as it has been previously shown for glutamate, further supporting the corelease of glutamate and zinc from mossy fibers.

Glycine- and GABA-mimetic Actions of Shilajit on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Mice

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated Na+ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a GABAA receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and GABAA receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.

Somatostatin Inhibits Gonadotropin Releasing Hormone Neuronal Activities in Juvenile Mice

BACKGROUND: The gonadotropin releasing hormone (GnRH) neurons perform a pivotal function in the central regulation of fertility. Somatostatin (SST) is an important neuromodulatory peptide in the central nervous system and alters neuronal activities via G protein- coupled SST receptors. A number of studies have shown that SST modulates the reproductive axis at the hypothalamic level. However, the precise action mechanisms of SST and related receptor subtypes have yet to be fully understood. In this study, we evaluated the direct effects of SST on GnRH neurons in juvenile mice. METHODS: Juvenile (postnatal days, < PND 30) GnRH-GFP transgenic mice expressing green fluorescent protein were used in this study. Acute coronal brain slices containing the preoptic area were prepared and all identified GnRH neurons were recorded using the gramicidin perforated-patch clamp technique; type II SST receptor (SSTR2) mRNA expression was evaluated via single cell reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: SST caused membrane hyperpolarization, depolarization, no response, or membrane hyperpolarization with a reduction of action potential. Most (57.7%, 30/52) of the GnRH neurons tested were hyperpolarized by SST and this SST-induced hyperpolarization was found to be concentration-dependent. The percentage of responses, membrane potential changes (MPC), and resting membrane potential (RMP) by SST were not significantly different in juvenile male and female GnRH neurons. The SST-induced hyperpolarization was maintained in the presence of tetrodotoxin (TTX), a sodium channel blocker, and an amino acid blocking cocktail (AABC) containing AP-5 (NMDA receptor antagonist), CNQX (non-NMDA glutamate receptor antagonist), picrotoxin (GABAA receptor antagonist), and strychnine (glycine receptor antagonist). SSTR2 mRNA was expressed on 10 (38%) among 26 GnRH neurons. Seglitide, an SSTR2 agonist, mimicked this SST-induced hyperpolarization (11/23 47.8%) and this response was maintained in the presence of TTX and AABC. CONCLUSION: Our data show that SST can exert potent inhibitory action against GnRH neuronal excitability via SSTR2 activation in juvenile mice.

The Neuroprotective Effects of 6-cyano-7-nitroquinoxalin-2,3-dione (CNQX) Via Mediation of Nitric Oxide Synthase on Hypoxic-ischemic Brain Injury in Neonatal Rats

PURPOSE: Current studies have demonstrated the neuroprotective effects of 6-cyano-7-nitroquinoxalin-2,3-dione (CNQX) in many animal models of brain injury, including hypoxic-ischemic (HI) encephlopathy, trauma and excitotoxicity, but limited data are available for those during the neonatal periods. Here we investigated whether CNQX can protect the developing rat brain from HI injury via mediation of nitric oxide synthase. METHODS: In an in vivo model, left carotid artery ligation was done in 7-day-old Sprague-Dawley (SD) rat pups. The animals were divided into six groups; normoxia (N), hypoxia (H), hypoxia with sham-operation (HS), hypoxia with operation (HO), HO treated with vehicle (HV), and HO treated with CNQX at a dose of 10 mg/kg (HC). Hypoxia was made by exposure to a 2 hr period in the hypoxic chamber (92% N2, 8% O2). In an in vitro model, embryonic cortical neuronal cell culture of SD rats at 18-day gestation was done. The cultured cells were divided into three groups: normoxia (N), hypoxia (H), and hypoxia treated with CNQX (HC). The N group was prepared in 5% CO2 incubators and the other groups were placed in 1% O2 incubators (94% N2, 5% CO2) for 16 hr. RESULTS: In the in vitvo and in vivo models, the expressions of iNOS and eNOS were reduced in the hypoxia group when compared to the normoxia group, whereas they were increased in the CNQX-treated group compared to the hypoxia group. In contrast, the expression of nNOS was showed reversely. CONCLUSION: CNQX has neuroprotective property over perinatal HI brain injury via mediation of nitric oxide synthase.

Effects and mechanisms of L-glutamate microinjected into nucleus ambiguus on gastric motility in rats / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>L-glutamate (L-GLU) is a major neurotransmitter in the nucleus ambiguus (NA), which can modulate respiration, arterial pressure, heart rate, etc. This study investigated the effects and mechanisms of L-GLU microinjected into NA on gastric motility in rats.</p><p><b>METHODS</b>A latex balloon connected with a pressure transducer was inserted into the pylorus through the forestomach for continuous recording of the gastric motility. The total amplitude, total duration, and motility index of gastric contraction waves within 5 minutes before microinjection and after microinjection were measured.</p><p><b>RESULTS</b>L-GLU (5 nmol, 10 nmol and 20 nmol in 50 nl normal saline (PS) respectively) microinjected into the right NA significantly inhibited gastric motility, while microinjection of physiological saline at the same position and the same volume did not change the gastric motility. The inhibitory effect was blocked by D-2-amino-5-phophonovalerate (D-AP5, 5 nmol, in 50 nl PS), the specific N-methyl-D-aspartic acid (NMDA) receptor antagonist, but was not influenced by 6-cyaon-7-nitroquinoxaline-2,3-(1H,4H)-dione (CNQX) (5 nmol, in 50 nl PS), the non-NMDA ionotropic receptor antagonist. Bilateral subdiaphragmatic vagotomy abolished the inhibitory effect by microinjection of L-GLU into NA.</p><p><b>CONCLUSIONS</b>Microinjection of L-GLU into NA inhibits the gastric motility through specific NMDA receptor activity, not non-NMDA receptor activity, and the efferent pathway is the vagal nerves.</p>

Electrophysiological Characterization of AMPA and NMDA Receptors in Rat Dorsal Striatum

The striatum receives glutamatergic afferents from the cortex and thalamus, and these synaptic transmissions are mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors. The purpose of this study was to characterize glutamate receptors by analyzing NMDA/AMPA ratio and rectification of AMPA and NMDA excitatory postsynaptic currents (EPSCs) using a whole-cell voltage-clamp method in the dorsal striatum. Receptor antagonists were used to isolate receptor or subunit specific EPSC, such as (DL)-2-amino-5-phosphonovaleric acid (APV), an NMDA receptor antagonist, ifenprodil, an NR2B antagonist, CNQX, an AMPA receptor antagonist and IEM-1460, a GluR2-lacking AMPA receptor blocker. AMPA and NMDA EPSCs were recorded at -70 and +40 mV, respectively. Rectification index was calculated by current ratio of EPSCs between +50 and -50 mV. NMDA/AMPA ratio was 0.20+/-0.05, AMPA receptor ratio of GluR2-lacking/GluR2-containing subunit was 0.26+/-0.05 and NMDA receptor ratio of NR2B/NR2A subunit was 0.32+/-0.03. The rectification index (control 2.39+/-0.27) was decreased in the presence of both APV and combination of APV and IEM-1460 (1.02+/-0.11 and 0.93+/-0.09, respectively). These results suggest that the major components of the striatal glutamate receptors are GluR2-containing AMPA receptors and NR2A-containing NMDA receptors. Our results may provide useful information for corticostriatal synaptic transmission and plasticity studies.

Effect of antagonism of glutamate receptors in the PVN region on baroreflex in conscious rats / 中国应用生理学杂志

<p><b>AIM</b>To investigate the possible involvement of glutamate(Glu) in the paraventricular nucleus (PVN) in the central regulation of baroreflex.</p><p><b>METHODS</b>The baroreflex was induced by intravenous injection of phenylephrine in conscious rats, and the extracellular concentration of Glu in the PVN region was measured by microdialysis and high performance liquid chromatography (HPLC) techniques. To determine whether the observed Glu release was involved in the baroreflex, NMDA and non-NMDA receptor antagonists, MK-801 and CNQX, were perfused in the PVN region during baroreflex.</p><p><b>RESULTS</b>During baroreflex, the Glu concentration in the PVN region immediately increased to 384.82% +/- 91.77% of basal level (P < 0.01). (2) During baroreflex, direct perfusion of MK-801 and CNQX in the PVN were attenuated the increase of blood pressure and enhanced the decrease of HR (P < 0.01),resulting a significant increase in baroreflex sensitivity (P < 0.01).</p><p><b>CONCLUSION</b>Glutamate in PVN is involved in central regulation of baroreflex, which may inhibit baroreflex via ionothopic glutamate receptors.</p>

Combined Application of Bicuculline and 4-Aminopyridine-Induced Epileptiform Activity are Resistant to Conventional Anticonvulsants and AMPA in Young Rat Visual Cortex / 대한간질학회지

PURPOSE: The goal of the present study was to find out whether blockade of GABAergic synaptic transmission by bicuculline (BIC) in the presence of 4-aminopyridine (4-AP) would lead to expression or suppression of epileptiform activity in the immature brain and to observe the effect of commonly used anticonvulsants (valproic acid (VPA), carbamazepine (CBZP)) and 6-cyano-7-nitroquinoxalinedione (CNQX) on that epileptiform activity. METHODS: The visual cortex slices were obtained from 14-18 day-old Sprague-Dawley rats. Extracellular cellular recording was performed to observe the induction of epileptiform activity perfused by artificial CSF (ACSF) with combined application of BIC and 4-AP and the effect of VPA, CBZP and CNQX on that epileptiform activity for at least 1 hour. RESULTS: Epileptiform activity perfused by ACSF with combined application of BIC and 4-AP was insensitive to commonly used anticonvulsants (VPA, CBZP) and sensitive to CNQX. CONCLUSION: This study suggests that the epileptiform activity induced by combined application of BIC and 4-AP is present even in immature visual cortex slices. And, the blockade of GABAergic inhibition by BIC under 4-AP showed the increase of immature brain excitability as mature brain. The attenuation of that epileptiform activity by a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonist (CNQX) showed that AMPA receptor had relevance to the induction of that epileptiform activity.

Effect of Potassium, Bicuculline and CNQX on Epileptiform Activity Induced by Pilocarpine in the Rat Visual Cortex Slice

BACKGROUND: The purpose of this study was to investigate the effect of potassium, bicuculline (BIC) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) on epileptiform activity induced by pilocarpine in the rat visual cortex slices. METHODS: In the rat visual cortex slices, we observed the change of pilocarpine-induced epileptiform discharges using extracellular recordings during perfusion of artificial cerebro-spinal fluid (ACSF) with various potassium concentrations ([K+], 2.5, 5, 7.5 and 10 mM) and ACSF with 10 micrometer BIC and 20 micrometer CNQX under 7.5 mM [K+]. RESULTS: Spontaneous interictal epileptiform activity induced by pilocarpine was observed in 5 mM or higher [K+] and ictal discharge was only detected in 7.5 mM [K+]. Increase of [K+] from 2.5 to 7.5 mM not only resulted in the increase of frequency and amplitude of epileptiform activity but also favored the transformation of pilocarpine-induced interictal activity into ictal activity in the rat visual cortex. However, in 10 mM [K+], the ictal discharge was unprovoked and interictal activity was provoked with decreased frequency and amplitude. The spontaneous ictal discharge was blocked but interictal activity was maintained with increased frequency and amplitude by BIC. Interictal and ictal activities were completely blocked by CNQX. CONCLUSIONS: These results suggested that the extracellular potassium concentration, GABA system, and non-NMDA mechanism seemed to be involved in the development and maintenance of pilocarpine-induced epileptiform activity in the rat visual cortex.

High K-induced Epileptiform Activity under GABA Antagonist and Carbamazepine in the Rat Visual Cortex / 대한소아신경학회지

PURPOSE: The goal of this study was to investigate the effect of increase of K on the excitability of the visual cortex under GABA antagonist, carbamazepine(CBZP), 6-cyano-7-nitroquinoxaline-dione disodium(CNQX) and D-(-)-2-amino-5-phosphonopentanoic acid(D-AP5) on the increase of K-induced epileptiform activity. METHODS: The visual cortex slices were obtained from Sprague-Dawley rats. Extracellular recordings were performed to observe the induction of epileptiform discharges perfused by artificial CSF(ACSF) with an increase of K and the effect of 0.5 and 1 mM CBZP, 10 micrometer CNQX and 50 micrometer D-AP5 on the increase of K-induced epileptiform activity. RESULTS: Spontaneous epileptiform activities were increased by ACSF with 10 mM K under bicuculline compared to 4 mM K. CBZP blocked and 10 micrometer CNQX and 50 micrometer D-AP5 decreased the 10 mM K-induced spontaneous epileptiform activity. CONCLUSION: An increase of K augmented spontaneous epileptiform activity. This experimental model increased the excitability of the brain, which may be influenced by GABA. CBZP blocked the increase of K-induced epileptiform activity, which showed the increase of excitability. An increase of K-induced epileptiform activity was decreased by CNQX and D-AP5, which may show the attenuation of voltage-dependent low magnesium effect and decrease the excitability in terms of synapse induction.

N-methyl-D-aspartate (NMDA) and Non-NMDA Receptors are Involved in the Production and Maintenance of Nociceptive Responses by Intraplantar Injection of Bee Venom and Melittin in the Rat

Whole bee venom (WBV) and its major component, melittin, have been reported to induce long-lasting spontaneous flinchings and hyperalgesia. The current study was designed to elucidate the peripheral and spinal mechanisms of N-methyl-D-aspartate (NMDA) and non-NMDA receptors by which intraplantar (i.pl.) injection of WBV and melittin induced nociceptive responses. Changes in mechanical threshold and flinching behaviors were measured after the injection of WBV (0.04 mg or 0.1 mg/paw) and melittin (0.02 mg or 0.05 mg/paw) into the mid-plantar area of a rat hindpaw. MK-801 and CNQX (6-cyano-7-nitroquinoxaline-2, 3-dione disodium) were administered intrathecally (i.t. 10microgram) or i.pl. (15microgram) 15 min before or i.t. 60 min after i.pl. WBV and melittin injection. Intrathecal pre- and post- administration of MK-801 and CNQX significantly attenuated the ability of high dose WBV and melittin to reduce paw withdrawal threshold (PWT). In the rat injected with low dose, but not high dose, of WBV and melittin, i.pl. injection of MK-801 effectively suppressed the decrease of PWTs only at the later time-points, but the inhibitory effect of CNQX (i.pl.) was significant at all time-point after the injection of low dose melittin. High dose WBV- and melittin-induced spontaneous flinchings were significantly suppressed by i.t. administration of MK-801 and CNQX, and low dose WBV- and melittin-induced flinchings were significantly reduced only by intraplantarly administered CNQX, but not by MK-801. These experimental flinchings suggest that spinal, and partial peripheral mechanisms of NMDA and non-NMDA receptors are involved in the development and maintenance of WBV- and melittin-induced nociceptive responses.

In Vitro Effect of Carbamazepine, D-(-)-2-Amino-5-Phosphonopentanoic Acid and 6-Cyano-7-Nitroquinoxaline-Dione on Pentylenetetrazole-Induced Epileptiform Activity in Young Rat Visual Cortex / 대한간질학회지

PURPOSE: Carbamazepine (CBZ) has little untoward effect in behavior, cognition and psychosocial aspects and commonly used in children. But, CBZ can sometimes worsen tonic-clonic seizures. The goal of the present study was to investigate the effect of CBZ, D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5) and 6-cyano-7-nitroquinoxaline-dione (CNQX) on pentylenetetrazole (PTZ)-induced epileptiform activity in young rat visual cortex. METHODS: The visual cortex slices were obtained from 14-18 day-old Sprague-Dawley rats. We observed the effect of CBZ, D-AP5 and CNQX on PTZ-induced epileptiform activity from visual cortex slices in vitro. RESULTS: The latency of PTZ-induced epileptiform activity was prolonged by 0.5 and 1 mM CBZ, the duration and frequency were decreased by 1 mM CBZ and amplitude was decreased by 0.5 and 1 mM CBZ. 3 mM CBZ and 20 micrometer CNQX blocked PTZ-induced epileptiform activity and 50 micrometer D-AP5 attenuated. CONCLUSION: This study suggest that CBZ may have more effect on epileptiform activity originated from visual cortex and differential effect according to brain region in young rat. Also, NMDA and AMPA mechanism may involve in PTZ-induced epileptiform activity originated from young rat visual cortex.

Tetraethylammonium-induced Epileptiform Activity and its Modification by GABAA Antagonist in the Rat Visual Cortex / 대한소아신경학회지

PURPOSE: The goal of this study was to investigate the effect of tetraethylammonium (TEA) on the excitability of visual cortex, and observe the induction of epileptiform activity. Also, it was aimed to define the characteristics of spontaneous activity and observe the effect of GABAA antagonist, NMDA antagonist and non-NMDA antagonist on the TEA-induced epileptiform activity. METHODS: The visual cortex slices in this study were obtained from 19 to 23 day-old Sprague-Dawley rats. Extracellular cellular recording was performed to observe the induction of epileptiform discharge perfused by artificial CSF containing 1, 5 and 10 mM TEA and the effect of 10 ?M 6-cyano-7-nitroquinoxaline-dione disodium(CNQX) and 50 microM D-(-)-2-amino-5-phosphonopentanoic acid(D-AP5) on the 10 mM TEA-induced epileptiform activity. RESULTS: Spontaneous epileptiform activities were observed in 5 and 10 mM TEA groups. The addition of 5 ?M BIC blocked the TEA-induced spontaneous ictal epileptiform activity but didn't block the TEA-induced spontaneous interictal epileptiform activity. The addition of 10 ?M CNQX shortened duration, decreased frequency and amplitude of the TEA-induced spontaneous epileptiform activity. The addition of 50 microM D-AP5 blocked the TEA-induced spontaneous ictal and interictal epileptiform activity. CONCLUSION: TEA induced the increased excitability in the visual cortex and spontaneous epileptiform activity. 5 ?M BIC blocked the TEA-induced spontaneous ictal epileptiform activity and GABAA antagonist BIC plays a role in limiting the epileptiform discharge. The TEA-induced spontaneous epileptiform activity induction was decreased by CNQX and blocked by D-AP5. NMDA and non-NMDA are required to modify the TEA-induced spontaneous epileptiform activity.

Properties of Low Magnesium Induced Epileptiform Activity in Rat Visual Cortex Slices / 대한간질학회지

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.

Bicuculline Induced Epileptiform Activity / 대한소아신경학회지

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.

4 Aminopyridine Induced Epileptiform Activity / 대한소아신경학회지

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.