Clinics in Developmental Medicine

Kindling and status epilepticus models of epilepsy: rewiring the brain.

A group of neurons with the characteristics of dentate gyrus granule cells was found at the hilar/CA3 border several weeks after pilocarpine- or kainic acid-induced status epilepticus. Intracellular recordings from pilocarpine-treated rats showed that these “granule-like” neurons were similar to normal granule cells (i.e., those in the granule cell layer) in membrane properties, firing behavior, morphology, and their mossy fiber axon. However, in contrast to normal granule cells, they were synchronized with spontaneous, rhythmic bursts of area CA3 pyramidal cells that survived status epilepticus. Saline-treated controls lacked the population of granule-like cells at the hilar/CA3 border and CA3 bursts.

In rats that were injected after status epilepticus with bromodeoxyuridine (BrdU) to label newly born cells, and also labeled for calbindin D28K (because it normally stains granule cells), many double-labeled neurons were located at the hilar/CA3 border. Many BrdU-labeled cells at the hilar/CA3 border also were double-labeled with a neuronal marker (NeuN). Taken together with the recent evidence that granule cells that are born after seizures can migrate into the hilus, the results suggest that some newly born granule cells migrate as far as the CA3 cell layer, where they become integrated abnormally into the CA3 network, yet they retain granule cell intrinsic properties. The results provide insight into the physiological properties of newly born granule cells in the adult brain and suggest that relatively rigid developmental programs set the membrane properties of newly born cells, but substantial plasticity is present to influence their place in pre-existing circuitry.

http://cdr.rfmh.org/Publications/PDFs_Scharfman/Scharfman%202000%20J%20Neurosci.pdf

Granule-like neurons at the hilar/CA3 border after status epilepticus and their synchrony with area CA3 pyramidal cells: functional implications of seizure-induced neurogenesis.

Animal models of epilepsy for the development of antiepileptogenic and disease-modifying drugs. A comparison of the pharmacology of kindling and post-status epilepticus models of temporal lobe epilepsy.

Objective: The full anticonvulsant effect of the ketogenic diet (KD) can require weeks to develop in rats, suggesting that altered gene expression is involved. The KD typically is used in pediatric epilepsies, but is effective also in adolescents and adults. Our goal was to use microarray and complementary technologies in adolescent rats to understand its anticonvulsant effect. Methods: Microarrays were used to define patterns of gene expression in the hippocampus of rats fed a KD or control diet for 3 weeks. Hippocampi from control- and KD-fed rats were also compared for the number of mitochondrial profiles in electron micrographs, the levels of selected energy metabolites and enzyme activities, and the effect of low glucose on synaptic transmission. Results: Most striking was a coordinated upregulation of all (n 34) differentially regulated transcripts encoding energy metabolism enzymes and 39 of 42 transcripts encoding mitochondrial proteins, which was accompanied by an increased number of mitochondrial profiles, a higher phosphocreatine/creatine ratio, elevated glutamate levels, and decreased glycogen levels. Consistent with increased energy reserves, synaptic transmission in hippocampal slices from KD-fed animals was resistant to low glucose. Interpretation: These data show that a calorie-restricted KD enhances brain metabolism. We propose an anticonvulsant mechanism of the KD involving mitochondrial biogenesis leading to enhanced alternative energy stores. Ann Neurol 2006;60:223–235

Mitochondrial biogenesis in the anticonvulsant mechanism of the ketogenic diet.

Kainic acid seizures in the developing brain : status epilepticus and spontaneous recurrent seizures

The long-term behavioral and cognitive effects of seizures at different ages were studied using the kainic acid (KA) seizure model. Rats of postnatal (P) ages (in days) 5, 10, 20, 30, and 60 were administered KA intraperitoneally (i.p.), which induced status epilepticus for several hours, or an equivalent volume of saline. Occurrence of spontaneous recurrent seizures (SRS) was then monitored for 3 months by a closed-circuit videotaping system. Rats began behavioral testing on P80; a separate group of rats that received KA on P60 began testing on P120. Behavioral tests included the Morris water maze (visuospatial learning and memory), the open field test (response to a novel environment), and the handling test (emotionality). When tested on P80, KA-treated P5 and P10 rats had no demonstrable deficits on any test as compared with controls. KA-Treated P20 rats differed from controls only on the water maze spatial bias test. KA-Treated P30 rats had deficits in spatial bias, were more active in the open field, and were more aggressive when handled. KA-Treated P60 rats, whether tested on P80 or P120, had deficits in learning platform position and spatial bias in the water maze, were more active in the open field, and were more aggressive when handled. P60 rats with SRS performed poorer in water maze place learning and spatial bias testing, although the number of SRS did not correlate with overall task acquisition. Our findings suggest age-related behavioral and cognitive deficits after KA-induced seizures. Pubescents and adults had alterations in learning, memory, exploratory behavior, and response to handling, whereas younger animals had no obvious behavioral or cognitive deficits.

Age‐Dependent Cognitive and Behavioral Deficits After Kainic Acid Seizures

Summary: Purpose: Despite use of the ketogenic diet (KD) for >75 years its effectiveness or mechanism of action has been examined in few animal studies. Using the kindling model of epilepsy, we tested the anticonvulsant effectiveness and behavioral consequences of an experimental KD in adult rats.



Methods: Rats fully kindled from the amygdala were divided into KD-fed or standard rat diet-fed groups; diet treatment continued for 5 weeks. The KD approximated at 4:l (“classic”) ketogenic diet and consisted (by weight) of 70% fat, 14% protein, no carbohydrate, and appropriate vitamins, minerals and fiber; 92% of energy provided was contributed by fat and 8% was contributed by protein. Afterdischarge threshold and duration (ADT, ADD) and stage 5 seizure threshold and duration (ST, SD) were assessed weekly for 5 weeks. During week 3, learning and memory were tested by the water maze and the behavioral response to a novel environment was assessed by the open field test.



Results: Rats receiving the KD became ketonemic and had weight gains similar to those of control rats. As compared with rats receiving a standard diet, those fed the KD had an elevated ADT and ST for the first 2 weeks of treatment. The control and KD-fed groups did not differ with regard to ADD or SD at any time during the study, and both groups performed similarly in the water maze and open field test.



Conclusions: In the kindling model, the KD afforded transient protection against the focal generation of kindled seizures but not seizure spread. Rats that received the KD did not perform differently from control-fed rats on spatial learning or exploratory behavior tasks. Our results provide a promising model for study of the anticonvulsant mechanisms of ketosis.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1528-1157.1997.tb01461.x

Ketogenic diet : Effects on expression of kindled seizures and behavior in adult rats

To investigate the potential role of drug therapy in preventing or exacerbating seizure-related brain injury in the prepubescent brain, we administered kainic acid to rats at postnatal day 35. Therapy with daily phenobarbital was started directly before or 1 day after kainic acid was administered, and was continued through postnatal day 153. Rats receiving phenobarbital had therapeutic concentrations during most of the 24-hour dosing period, but also experienced supratherapeutic peak concentrations. The animals were subsequently tested using the water maze (a measure of visuospatial memory), open field (a measure of activity level), and handling tests (a measure of emotionality). The frequency of spontaneous recurrent seizures was monitored during and after phenobarbital therapy. Kainic acid resulted in status epilepticus on postnatal day 35 in all the rats that received it but those receiving phenobarbital first manifested a shorter and less severe status epilepticus as compared to the rats given kainic acid alone. Rats starting phenobarbital immediately before kainic acid was administered did not differ from control rats on behavioral testing and had no subsequent spontaneous recurrent seizures and no histological lesions. Rats receiving kainic acid alone performed significantly poorer than did control rats in the water maze, were more aggressive, had histological lesions, and manifested spontaneous recurrent seizures. As compared to the group treated only with kainic acid, rats receiving kainic acid followed by phenobarbital at postnatal days 36 to 153 manifested similar aggressiveness and histological lesions, similar frequency of spontaneous recurrent seizures after phenobarbital taper, and even greater disturbances in memory, learning, and activity level.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenobarbital modifies seizure‐related brain injury in the developing brain

The high fat, low carbohydrate, low protein ketogenic diet (KD) has been used to control refractory epilepsy in children since 1920, although its mechanism of action is unknown. Previous animal studies have shown that the KD can increase acute seizure threshold, but the effect of the KD on the process of epileptogenesis has not been studied. We tested the effect of an experimental KD on epileptogenesis in adult rats using the kainic acid (KA) model. P54 rats underwent KA-induced status epilepticus, followed by assignment to a control diet or a KD consisting of (by weight), 14% protein, 70% fat and no carbohydrate. KD-fed animals tolerated the diet and maintained ketosis. KD-fed rats had significantly fewer and briefer spontaneous recurrent seizures and less supragranular mossy fiber sprouting, although the degree of hippocampal pyramidal cell damage was similar in both groups. These results provide the first evidence that the KD retards epileptogenesis in an experimental model.

Carl E. Stafstrom

Papers

Kainic acid seizures in the developing brain : status epilepticus and spontaneous recurrent seizures

Age‐Dependent Cognitive and Behavioral Deficits After Kainic Acid Seizures

Ketogenic diet : Effects on expression of kindled seizures and behavior in adult rats

Phenobarbital modifies seizure‐related brain injury in the developing brain

Ketogenic diet reduces spontaneous seizures and mossy fiber sprouting in the kainic acid model.