Effects of long-stimulus intervals and scopolamine administration on hippocampal kindling

Using the low-frequency kindling procedure, we studied the effects of periodic 2-week stimulus-free intervals and chronic scopolamine administration on hippocampal kindling seizure development. In Experiment 1, rats were divided into two groups, interval group and no-interval group. In the interval group a 2-week stimulus interval was set after every five consecutive daily stimulations until the 21st stimulation. The number of stimulating pulses required for the triggering of epileptic afterdischarge, pulse-number threshold (PNT), was used as an indicator of the seizure thershold. PNT, afterdischarge duration (ADD) and behavioral seizure stage (BSS) of each induced seizure in the initial stage of kindling, kindling rate, seizure parameters at the completion of kindling were recorded and compared to the values of the no-interval, control group. Our result showed that PNT at the 6th stimulation, the first stimulation after the first 2-week stimulus interval increased significantly compared to control. Other seizure parameters did not differ significantly between the two groups. In Experiment 2 scopolamine hydrobromide, 0.5 and 1.0 mg/kg i.p., was administered 1 h before each electrical stimulation until each rat showed the stage-3 seizure. PNT, ADD and BSS in the initial stage of kindling, kindling rate for the stage-3 and -5 seizures, seizure parameters at the first stage-3 and -5 were recorded and compared to the values of saline-treated, control group. Although scopolamine 1.0 mg/kg increased PNT at the 5th stimulation compared to control, no other significant changes of the seizure parameters were found by scopolamine. Together with our previous studies, these results support our finding that physiological and pharmacological characteristics of the reduction of seizure threshold, but not of the development of induced seizures in the hippocampal kindling process are quite similar to those of long-term potentiation. Clinically our present findings suggest that occurrence of the first several seizures causes a long-lasting reduction of seizure threshold which should make the disease more intractable against treatment.     

Two types of neuroplasticities in the kindling phenomenon: effects of chronic MK-801 and methamphetamine

Using the low-frequency kindling technique, we studied the effects of chronic MK-801 and chronic methamphetamine (MAP) administration on hippocampal kindling seizure development. In experiment 1, MK-801 (0.05, 0.1 mg/kg i.p.) was administered 2 h before each electrical stimulation until kindling developed into stage-3 seizure. In experiment 2, we started daily electrical stimulations two weeks after the last injection of chronic MAP administration (6 mg/kg/day, 14 days). The number of stimulating pulses required for the triggering of epileptic afterdischarge (pulse-number threshold, PNT) was used as an indicator of the seizure threshold. PNT, afterdischarge duration (ADD) and behavioral seizure stage (BSS) of each induced seizure in the initial stage of kindling; the kindling rates for stage 3 and stage 5 seizures; seizure parameters at the completion of kindling of the drug-treated groups were recorded and compared to the values of each saline-treated control group. Our result showed that MK-801 administration prior to each electrical stimulation selectively and significantly increased PNT in the initial stage of kindling without affecting other seizure parameters. Chronic pretreatment of MAP caused a selective and significant decrease of PNT of the first two stimulations in the kindling process. Taken together with the previous studies, these results suggest that long-term potentiation plays an important role in the development of the excitability of seizure focus but not of the induced seizure's propagation in the hippocampal kindling phenomenon. Clinically MK-801 seems to be a more efficacious drug in preventing the induction of seizures than in suppressing the acquired seizures.     

Effects of phenobarbital and phenytoin on hippocampus generating seizures

We have recently reported some pharmacological studies using a kindling model of epilepsy induced with 1-3 HZ electrical stimulations, referred to as the low-frequency kindling. Since a previous study showed that the effects of psychotropic drugs on limbic seizures were dependent on the location of epileptic focus, we decided to study acute and chronic effects of anticonvulsants on the hippocampus generating seizures to compare with the results of a previous study of the amygdala generating seizures, which was done under the same conditions with this study. The number of stimulating pulses required for the triggering of epileptic afterdischarge (pulse-number threshold) was used as the indicator for the seizure threshold. Duration of after discharge (ADD), ictal and interictal behaviors of the subjected 7 cats, and serum drug levels were also recorded. A dose-dependent increase of serum drug levels was confirmed in each drug, and the values were well comparable with the optimal range in clinical use. In acute experiment PB 5 mg/kg p.o. produced no significant effect on PNT and ADD. PB 10 mg/kg increased PNT significantly (p less than 0.02) at 2 hrs after administration without affecting ADD, but 4 cats presented the seizure-stage regressions. PB 20 mg/kg increased PNT (p less than 0.02) and decreased ADD (p less than 0.02) with the seizure-stage regressions of all the tested cats at 2 hrs after administration, and increased PNT (p less than 0.05) without affecting ADD and seizure stage at 96 hrs after administration. PHT 5, 10, 20 mg/kg decreased PNT (p less than 0.05, 0.02, 0.02, respectively) without affecting ADD at 2 hrs after administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Positive transfer of audiogenic kindling to electrical hippocampal kindling in rats.

Audiogenic seizures in genetically susceptible rodents are provoked by intense acoustic stimulations which result in a tonic seizure associated with a short flattening of the EEG. These seizures have been shown to involve primarily brainstem structures. Daily exposure to sound for 30-40 days produced a permanent change in the evoked seizure with development of facial myoclonias, rearing and falling, or of tonic-clonic seizures accompanied by high amplitude cortical spike-and-wave discharges. Kindled audiogenic seizures appear similar to seizures kindled from amygdala or hippocampus, suggesting that repeated auditory stimulations cause a progressive propagation of the epileptic discharge toward limbic structures. To verify this hypothesis, the behavioral and EEG development of electrical hippocampal kindling has been studied in 7 non epileptic controls (NE), 8 acoustic susceptible (AS), and 8 audiogenic kindled rats (KAS). The behavioral and EEG development of the electrical hippocampal kindling was similar in the AS and the NE rats. However, 2 animals in the AS group but no controls exhibited behavioral running and bouncing during the course of hippocampal kindling. In the KAS group, the hippocampal kindling was clearly facilitated as compared to NE and AS: behavioral stage greater than or equal to 5 was reached in a mean of 4 stimulations in KAS versus 30 and 22 stimulations respectively in NE and AS groups. This positive transfer phenomenon suggests that during kindling of audiogenic seizures, epileptic discharge spreads from the brainstem to the forebrain and progressively involves the hippocampus.     

A biphasic changes in the seizure-threshold in kindling seizure development induced with low-frequency electrical stimulations

Seven cats were stimulated once a day with low-frequency electrical stimulations to assess the serial changes of development. Each animal had been implanted stereotaxically with a stimulating electrode into the left-side ventral hippocampus and with recording electrodes into the right-side ventral hippocampus, the bilateral dorsal hippocampus. We applied the stimulations at 10:00 AM, bipolarly with 2 mA-biphasic square-wave pulses (1 msec durations). The pulse-interval was set at 300 msec. If epileptic afterdischarge could not be triggered on EEG with this pulse-interval, a 100msec-interval stimulation was applied after 15 min-rest period. The number of stimulating pulses required for a triggering of afterdischarge was defined as pulse-number threshold (PNT) which was used as an indicator of the seizure-threshold. The duration of each seizure on EEG (afterdischarge duration, ADD) was also recorded and the seizure-related behaviors were classified into 5 stages as follows: 1, staring or immobility; 2 appearance of facial twitching or head nodding ; 3, tonic convulsions of the right-side fore-paw or a head turning toward the right-side; 4, generalized clonic convulsions; 5, generalized convulsions with a falling down. The kindling procedure completed within a mean of 36.5 days, and all the animals presented stage-5 seizures. At the completion of kindling, PNT was determined at 10.5 +/- 1.8 (mean +/- SE). During the kindling process PNT showed a sudden decrease in the initial part of stage-1 (within a mean of 3.8 days) and a gradual increase from stage-3 to stage-5. ADD showed a simple increasing function of the development of seizure-stage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute Effect of Anticonvulsants on Amygdaloid Kindled Seizures Induced with Low-Frequency Stimulations

Acute effects of several antiepileptic drugs on low-frequency amygdaloid-kindled seizures were assessed. The number of stimulating pulses required for the provocation of epileptic afterdischarge (pulse-number threshold, PNT) was used as an indicator for the seizure-generating threshold. The duration of epileptic afterdischarge (AD duration) was used as an indicator for the severity of the induced seizures. Phenytoin (PHT) and carbamazepine (CBZ) reduced AD duration more than did elevating PNT. Conversely, phenobarbital (PB) and diazepam (DZP) elevated PNT more than did reducing AD duration. Weak effects on the two indicators, valproic acid (VPA) and ethosuximide (ESM), were observed. Low-frequency kindling may be a useful experimental model of epilepsy in drug-assessments.     

Effects of chronic treatment with haloperidol and methamphetamine on hippocampal kindled seizures in the cat

We assessed the effects of chronic treatment with haloperidol (0.5-2 mg/kg/day, p.o., 17 days) and methamphetamine (1-2 mg/kg/day, p.o., 17 days; 4 mg/kg/day, p.o. 9 days) on hippocampal kindled seizures using a kindling procedure with low-frequency (about 3 Hz) electrical stimulation in cats. The number of stimulating pulses required to trigger epileptic afterdischarge (pulse-number threshold, PNT) was considered an indicator of seizure threshold. Haloperidol, 0.5 and 1.0 mg/kg, reduced the duration of epileptic afterdischarge (afterdischarge duration, ADD) without affecting PNT, and 2.0 mg/kg strongly reduced PNT and ADD. Methamphetamine, 2.0 mg/kg, reduced PNT and ADD, and 4.0 mg/kg preferentially reduced PNT. The effects of the two drugs on hippocampal kindled seizures were found to be partially opposite to those on amygdala kindled seizures, suggesting the different response of these limbic structures to dopamine receptor manipulation.     

Acute effect of TRH, flunarizine, lithium and zotepine on amygdaloid kindled seizures induced with low-frequency stimulation

We assessed the acute effects of various drugs on amygdaloid kindled seizures induced with low-frequency stimulations. We used the number of stimulating pulses required for the induction of epileptic afterdischarge (pulse-number threshold; PNT) as an indicator of the seizure generating threshold and the duration of induced seizures (AD duration; ADD) as an indicator of the seizures. TRH increased the PNT without affecting the ADD at a high dose (1.2 mg/kg). Flunarizine decreased the PNT and ADD simultaneously at a high dose (50 mg/kg). Lithium increased the PNT without affecting the ADD at two doses (100 mg/kg, 200 mg/kg). Zotepine decreased the PNT without affecting the ADD at two doses (8 mg/kg, 16 mg/kg). We propose that the technique of low-frequency kindling is a useful experimental model in assessing the effects of antipsychotic or antiepileptic drugs on the excitability of the limbic regions.     

Acute Effect of TRH, Fhmarizine, Lithium and Zotepine on Amygdaloid Kindled Seizures Induced with Low-Frequency Stimulation

Abstract: We assessed the acute effects of various drugs on amygdaloid kindled seizures induced with low-frequency stimulations. We used the number of stimulating pulses required for the induction of epileptic afterdischarge (pulse-number threshold; PNT) as an indicator of the seizure generating threshold and the duration of induced seizures (AD duration; ADD) as an indicator of the seizures. TRH increased the PNT without affecting the ADD at a high dose (1.2 mg/kg). Flunarizine decreased the PNT and ADD simultaneously at a high dose (50 mg/kg). Lithium increased the PNT without affecting the ADD at two doses (100 mg/kg, 200 mg/kg). Zotepine decreased the PNT without affecting the ADD at two doses (8 mg/kg, 16 mg/kg). We propose that the technique of low-frequency kindling is a useful experimental model in assessing the effects of antipsychotic or antiepileptic drugs on the excitability of the limbic regions.     

Deep brain stimulation of the substantia nigra pars reticulata exerts long lasting suppression of amygdala-kindled seizures

Deep brain stimulation (DBS) has been used to treat a variety of neurological disorders including epilepsy. However, we have limited knowledge about effective target areas, optimal stimulation parameters, and long-term effect of DBS on epileptic seizures. Here we examined the effects of DBS of the substantia nigra pars reticulata (SNr) on amygdala-kindled seizures. Microwire electrodes were implanted into the SNr and amygdala of adult male rats. When stage 5-kindled seizures were achieved by daily amygdala kindling, high frequency stimulation was delivered to the SNr bilaterally 1 s after cessation of kindling. Our DBS protocol completely blocked kindled seizures in 10 out of 23 (43.5%) rats studied. Furthermore, when the same amygdala kindling procedure was performed 24 h later without DBS, the kindling failed to elicit any seizure signs in 6 of these 10 rats. Some of the post-DBS period of seizure suppression lasted for up to 4 days. In other 3 rats, only mild stage 1 to 2 seizures appeared following amygdala kindling. Only 1 of the 10 rats for which DBS had blocked kindled seizures exhibited full-scale 5 stage-kindled seizures 24 h after DBS. These results suggest that highly plastic neural networks are involved in amygdala-kindled seizures and that DBS, if well timed with the onset of amygdala kindling, may exert long lasting effects on the networks that may prevent the recurrence of kindled seizures.     

An ontogenetic study of kindling using rapidly recurring hippocampal seizures

The present study investigated the acquisition and retention of kindling in immature rats. Postnatal (PN) 7-28-day-old rats were electrically kindled in the ventral hippocampus. Ten-second, 20-Hz stimulus trains were delivered every 5 min for 6 h on one day (short interval rapidly recurring hippocampal seizures, RRHS) or every 30 min for 9 h on each of two consecutive days (long interval RRHS). Afterdischarge durations (ADD) and behavioral seizure scores (BSS) were recorded following each stimulation. Animals of all ages kindled with both short and long interval RRHS, as manifested by lengthening of ADD and increasing BSS. With short interval RRHS, the course of kindling was erratic; with long interval RRHS, kindling proceeded smoothly over both test days. In PN 14-28 rats, the degree of kindling obtained on the first day of long interval RRHS was retained at the start of the second experimental day. In contrast, PN 7 rats showed a transient decrease in ADD and BSS from day 1 to day 2. Afterdischarge thresholds declined with maturation. Among the PN 14-28 animals, younger rats exhibited longer seizures at the outset of kindling and proceeded through kindling faster. Once established, kindled motor seizures also occurred with 2-s, 50-Hz stimulus trains. We conclude that rapid kindling occurs at all ages; however, PN 7 rats are less capable of retaining the kindling effect than are older rats.     

Antiepileptic Effects of MK-801, a Noncompetitive NMDA-Receptor Antagonist, in the Low-Frequency Kindling Model of Epilepsy

Abstract: We assessed the acute effect of MK-801 (0.05–0.7 mg/kg), a noncompetitive NMDA-receptor antagonist, on hippocampus-kindled seizures induced with low-frequency (2 Hz) electrical stimulations. MK-801 dose-dependently increased the seizure threshold (PNT, the number of stimulating pulses required for the triggering of epileptic dterdischarge), whereas most of the previous studies which assessed the effect of MK-801 on kindled seizures could not detect the elevation of seizure threshold by MK-801. In addition MK-801 decreased the severity of induced seizures at low doses at which previous studies could not detect the antiepileptic effect of MK-801, suggesting that the low-frequency kindling technique might be a more sensitive and reliable model of epilepsy than the conventional high-frequency kindling technique.     

Effects of Chronic Treatment of Methamphetamine and Imipramine on Amygdaloid Seizure's Generation

Abstract: We assessed the effects of chronic treatment of methamphetamine (1–2 mg/kg/day, i.p., 17 days) and imipramine (2–8 mg/kg/day, P.o., 17 days) on amygdala-generating seizures using the kindling method induced by low-frequency electrical stimulations. The number of stimulating pulses required for the triggering of epileptic after-discharge (pulse-number threshold: PNT) is the indicator of seizure generating threshold. A PNT elevation followed by its reduction occurred, compared to the pretreatment level, during a 2 mg/kg/day chronic methamphetamine treatment. A reduction in the PNT and triggered afterdischarge durations occurred during a chronic imipramine treatment. These results indicate that both methamphetamine and imipramine reduced the seizure generating threshold by repeated applications. It is suggested that this finding might be related to the psychoactive potency and associated neurochemical changes which are known to be caused by these drugs.     

Effects of chronic treatment of methamphetamine and imipramine on amygdaloid seizure's generation

We assessed the effects of chronic treatment of methamphetamine (1-2 mg/kg/day, i.p., 17 days) and imipramine (2-8 mg/kg/day, p.o., 17 days) on amygdala-generating seizures using the kindling method induced by low-frequency electrical stimulations. The number of stimulating pulses required for the triggering of epileptic afterdischarge (pulse-number threshold: PNT) is the indicator of seizure generating threshold. A PNT elevation followed by its reduction occurred, compared to the pretreatment level, during a 2 mg/kg/day chronic methamphetamine treatment. A reduction in the PNT and triggered afterdischarge durations occurred during a chronic imipramine treatment. These results indicate that both methamphetamine and imipramine reduced the seizure generating threshold by repeated applications. It is suggested that this finding might be related to the psychoactive potency and associated neurochemical changes which are known to be caused by these drugs.     

Suppression of limbic motor seizures by electrical stimulation in thalamic reticular nucleus

Kindling is a model of temporal lobe epilepsy in which repeated electrical stimulations in limbic areas lead to progressive increase of seizure susceptibility, culminating in generalized convulsions and the establishment of a permanent epileptic syndrome. We studied here the effect of stimulations in the thalamic reticular nucleus (TRN) on the development of seizures and hippocampal hyperexcitability in kindling elicited from the ventral hippocampus in rats. Animals given 12 kindling stimulations per day with 30-min intervals for 4 consecutive days developed generalized convulsions on day 4. Stimulations in TRN delivered simultaneously with those in the hippocampus induced marked suppression of seizure generalization. Similarly, the number of generalized seizures and the duration of behavioral convulsions were reduced when rats subjected to 40 kindling stimulations with 5-min intervals during about 3 h were costimulated in the TRN. The anticonvulsant effect of TRN costimulation was detected also when rats were test-stimulated in the hippocampus at 24 h and 2 and 4 weeks after the initial 40 hippocampal stimulations. Our data provide the first evidence that TRN stimulations can act to suppress limbic motor seizures in hippocampal kindling and suggest a new approach for seizure control in temporal lobe epilepsy.     

Experimental Models of Temporal Lobe Epilepsy: New Insights from the Study of Kindling and Synaptic Reorganization

Summary: Temporal lobe epilepsy is a common localization-related epileptic syndrome characterized by complex partial seizures, ictal and interictal epileptic discharges arising from limbic structures of the temporal lobe, and association with hippocampal sclerosis. Temporal lobe epilepsy may follow perinatal injury and febrile convulsions, may be progressive, and frequently becomes refractory to standard antiepileptic therapy. The neurobiology that underlies these features of temporal lobe epilepsy is not known. Recent studies in experimental models have provided new insights that may help clarify the relationship of seizures, hippocampal sclerosis, and temporal lobe epilepsy. Observations from the study of the hippocampus with kainic acid-induced lesions, the kindling model, and other experimental models of epilepsy have demonstrated that seizures induce structural and electrophysiologic alterations in hippocampal pathways that may lead to increased excitability and could play a role in the development and progression of temporal lobe epilepsy. These alterations include mossy fiber synaptic reorganization, induction of NMDA-mediated synaptic transmission, and progressive hippocampal neuronal loss induced by brief kindled seizures. Some of the structural alterations induced by kindling have also been observed in the human epileptic temporal lobe, raising the possibility that mechanisms operative in kindling may play a role in the pathogenesis of hippocampal sclerosis and in the syndrome of human temporal lobe epilepsy.     

Increased susceptibility to hippocampal and amygdala kindling following intrahippocampal kainic acid

The effects of unilateral intrahippocampal injection of kainic acid, a potent neuroexcitant and neurotoxin, on subsequent susceptibility to kindling of the contralateral hippocampus or contralateral amygdala were investigated in albino rats. At the chosen doses (0.20 to 1.25 micrograms dissolved in physiologic saline), the kainic acid-induced lesion was confined to the injected hippocampus and in two cases the ipsilateral entorhinal cortex; never were there contralateral lesions. Approximately 2 to 6 weeks post-injection, each animal received daily afterdischarge-producing electrical stimulations until stage 5 kindled limbic seizures occurred. Kindling in pretreated animals was significantly accelerated compared with controls; the hippocampal kindling rate decreased from 13.2 stimulations to 3.7, the amygdala kindling rate from 7.8 stimulations to 3.0. Many treated animals had first-stimulation stage 5 seizures, compared with none for controls. Importantly, this facilitation of kindling was not reversed by suppression of the acute, induced seizures with the anticonvulsants, diazepam and phenobarbital, which have repeatedly been demonstrated to effectively suppress limbic kindling. Such results, considered together with findings from the literature, suggest that partial kindling does not occur during kainic acid-induced seizures, and that the observed susceptibility to kindling and other epileptogenic agents subsequent to kainic acid treatment may in fact be related to neurophysiologic and neurochemical consequences of kainic acid-induced lesions.     

Kindling in developing animals: expression of severe seizures and enhanced development of bilateral foci

In adult rats, alternating stimulations between two limbic sites can result in one site kindling normally, while the other is retarded in an early non-generalized kindling stage. This phenomenon has been named kindling antagonism. In this report, we present data indicating that kindling antagonism does not occur in 16-day-old rats. Instead, 16-day-old rats receiving alternating stimulations in the amygdala and hippocampus develop progressively more severe seizures. Kindling with alternate stimulations is elicited at a much faster rate at the two foci compared to kindling from a single site, either the hippocampus or amygdala. All groups develop generalized seizures including seizure stages 6 and 7, consisting of wild jumping, running with vocalizations and tonus. These seizures appear after relatively few stimulations in the pup, in comparison to the adult. The results indicate that the immature brain is less able to suppress the generalization of seizures than the adult. The age-specific enhanced development of bilateral foci may be due to underdeveloped inhibitory systems and may underlie the propensity of the immature CNS to develop multifocal seizures.     

Temporal sequence of ictal discharges propagation in the corticolimbic basal ganglia system during amygdala kindled seizures in freely moving rats

We used a multiple channel, single unit recording technique to investigate the neural activity in different corticolimbic and basal ganglia regions in freely moving rats before and during generalized amygdala kindled seizures. Neural activity was recorded simultaneously in the sensorimotor cortex (Ctx), hippocampus, amygdala, substantia nigra pars reticulata (SNr) and the subthalamic nucleus (STN). We observed massive synchronized activity among neurons of different brain regions during seizure episodes. Neurons in the kindled amygdala led other regions in synchronized firing, revealed by time lags of neurons in other regions in crosscorrelogram analysis. While there was no obvious time lag between Ctx and SNr, the STN and hippocampus did lag behind the Ctx and SNr in correlated firing. Activity in the amygdala and SNr contralateral to the kindling stimulation site lagged behind their ipsilateral counterparts. However, no time lag was found between the kindling and contralateral sides of Ctx, hippocampus and STN. Our data confirm that the amygdala is an epileptic focus that emits ictal discharges to other brain regions. The observed temporal pattern indicates that ictal discharges from the amygdala arrive first at Ctx and SNr, and then spread to the hippocampus and STN. The simultaneous activation of both sides of the Ctx suggests that the neocortex participates in kindled seizures as a unisonant entity to provoke the clonic motor seizures. Early activation of the SNr (before the STN and hippocampus) points to an important role of the SNr in amygdala kindled seizures and supports the view that different SNr manipulations may be effective ways to control seizures.     

Expression of connexin 30 and connexin 32 in hippocampus of rat during epileptogenesis in a kindling model of epilepsy

Objective Understanding the molecular and cellular mechanisms underlying epileptogenesis yields new insights into potential therapies that may ultimately prevent epilepsy.Gap junctions(GJs) create direct intercellular conduits between adjacent cells and are formed by hexameric protein subunits called connexins(Cxs).Changes in the expression of Cxs affect GJ communication and thereby could modulate the dissemination of electrical discharges.The hippocampus is one of the main regions involved in epileptogenesis and has a wide network of GJs between different cell types where Cx30 is expressed in astrocytes and Cx32 exists in neurons and oligodendrocytes.In the present study,we evaluated the changes of Cx30 and Cx32 expression in rat hippocampus during kindling epileptogenesis.Methods Rats were stereotaxically implanted with stimulating and recording electrodes in the basolateral amygdala,which was electrically stimulated once daily at afterdischarge threshold.Expression of Cx30 and Cx32,at both the mRNA and protein levels, was measured in the hippocampus at the beginning,in the middle(after acquisition of focal seizures),and at the end(after establishment of generalized seizures) of the kindling process,by real-time PCR and Western blot.Results Cx30 mRNA expression was upregulated at the beginning of kindling and after acquisition of focal seizures.Then it was downregulated when the animals acquired generalized seizures.Overexpression of Cx30 mRNA at the start of kindling was consistent with the respective initial protein increase.Thereafter,no change was found in protein abundance during kindling.Regarding Cx32,mRNA expression decreased after acquisition of generalized seizures and no other significant change was detected in mRNA and protein abundance during kindling.Conclusion We speculate that Cx32 GJ communication in the hippocampus does not contribute to kindling epileptogenesis.The Cx30 astrocytic network localized to perivascular regions in the hippocampus is,however,overexpressed at the initiation of kindling to clear excitotoxic molecules from the milieu.