Growth-associated phosphoprotein expression is increased in the supragranular regions of the dentate gyrus following pilocarpine-induced seizures in rats

Neuroplasticity has been investigated considering the neuronal growth-associated phosphoprotein as a marker of neuronal adaptive capabilities. in the present work, studying the hippocampal reorganization observed in the epilepsy model induced by pilocarpine, we carried out quantitative western blotting associated with immunohistochemistry to determine the distribution of growth-associated phosphoprotein in the hippocampus of rats in acute, silent and chronic periods of this epilepsy model. the fibers and punctate elements from the inner molecular layer of the dentate gyrus were strongly immunostained in animals killed 5 h after status epilepticus, compared with the same region in control animals. Rats presenting partial seizures showed no alterations in the immunostaining pattern compared with saline-treated animals. the hippocampal dentate gyrus of animals during the seizure-free period and presenting spontaneous recurrent seizures was also characterized by strong growth-associated phosphoprotein immunostaining of fibers and punctate elements in the inner molecular layer, contrasting with the control group. As determined by western blotting analysis, growth-associated phosphoprotein levels increased following status epilepticus and remained elevated at the later time-points, both during the silent period and during the period of chronic recurring seizures. Pilocarpine-treated animals, which did not develop status epilepticus, showed no change in growth-associated phosphoprotein levels, indicating that status epilepticus is important to induce growth-associated phosphoprotein overexpression.The measurement of this overexpression could represent one of the early signals of hippocampal reorganization due to status epilepticus-induced damage. (C) 1999 IBRO. Published by Elsevier B.V.Escola Paulista Med, UNIFESP, Disciplina Neurol Expt, BR-04023900 São Paulo, SP, BrazilEscola Paulista Med, UNIFESP, Disciplina Bioquim, BR-04023900 São Paulo, SP, BrazilEscola Paulista Med, UNIFESP, Disciplina Neurol Expt, BR-04023900 São Paulo, SP, BrazilEscola Paulista Med, UNIFESP, Disciplina Bioquim, BR-04023900 São Paulo, SP, BrazilWeb of Scienc

Glucose utilization during interictal intervals in an epilepsy model induced by pilocarpine: A qualitative study

Purpose: Interictal intervals in pilocarpine-induced chronic epilepsy are characterized by apparent normal electrographic activity and longer sleep periods or drowsiness or both. Sparse information exists concerning the neural network activity during these seizure-free intervals. in our research, all [C-14]2-deoxy-D-glucose (2DG) autoradiographic technique was used to investigate interictal changes in the metabolism of the epileptic rat brain.Methods: Epileptic mts were monitored by video-EEG for similar to 120 days, with [C-14]2DG injected after a seizure-free interval of greater than or equal to 24 h.Results: Autoradiographic analysis revealed an increase in glucose utilization by several brain regions; the most consistent increase was found in the lateral posterior thalamic nucleus and prerectal region.Conclusions: These findings suggest that the lateral posterior thalamic nucleus and the prerectal region may be involved in cerebral circuits inhibiting epileptic activity during interictal intervals

Glucose utilization during interictal intervals in an epilepsy model induced by pilocarpine: A qualitative study

Purpose: Interictal intervals in pilocarpine-induced chronic epilepsy are characterized by apparent normal electrographic activity and longer sleep periods or drowsiness or both. Sparse information exists concerning the neural network activity during these seizure-free intervals. in our research, all [C-14]2-deoxy-D-glucose (2DG) autoradiographic technique was used to investigate interictal changes in the metabolism of the epileptic rat brain.Methods: Epileptic mts were monitored by video-EEG for similar to 120 days, with [C-14]2DG injected after a seizure-free interval of greater than or equal to 24 h.Results: Autoradiographic analysis revealed an increase in glucose utilization by several brain regions; the most consistent increase was found in the lateral posterior thalamic nucleus and prerectal region.Conclusions: These findings suggest that the lateral posterior thalamic nucleus and the prerectal region may be involved in cerebral circuits inhibiting epileptic activity during interictal intervals.UNIFESP, EPM, BR-04023900 São Paulo, BrazilUNIFESP, EPM, BR-04023900 São Paulo, BrazilWeb of Scienc

Mitogen-activated protein kinase is increased in the limbic structures of the rat brain during the early stages of status epilepticus

Systemic administration of pilocarpine (PILO) in adult rat produces acute limbic seizures leading to states epilepticus. Recent studies have shown the activation of mitogen-activated protein kinase (MAPK) cascades during experimentally induced seizures. MAPK activation may be triggered by glutamatergic stimulation and may play a key role in signal transduction pathways, in the present study, immunocytochemistry was used to analyze the spatiotemporal distribution pattern of the MARK protein and its active form (A-MAPK) following PILO-induced status epilepticus, MAPK and A-MARK immunoreactivities exhibited different patterns of distribution in the brain of normal and epileptic rats. the saline-treated rats, as well as the animals that received PILO but did not evolve to status epilepticus, showed a weak but selective MAPK immunoreactivity, detected in the hippocampal pyramidal neurons, dentate gyrus, hilus, CA3, CA1, and entorhinal, piriform, and cingulate cortices. A-MARK immunoreactivity was instead observed only in neurites of the CA3 and hilus and in cells of the entorhinal and piriform cortices, in PILO-treated rats, between 30 and 60 min after states epilepticus there was an increase of the immunoreactivity to both antibodies, which were differently distributed throughout several structures of the limbic system. the immunostaining showed a slight decrease after 5 h of states epilepticus, However, MARK and A-MARK immunopositivities decreased markedly after 12 h of states epilepticus, returning almost to the basal expression. These findings are consistent with a spatial and time-dependent MAPK expression in selected limbic structures, and its activation could represent an initial trigger for neuronal modifications that may take part in the mechanism underlying acute epileptogenesis and in longlasting neuropathological changes of the PILO model of epilepsy. (C) 1998 Elsevier Science Inc.UNIFESP, EPM, Dept Expt Neurol, São Paulo, BrazilUNIFESP, EPM, Dept Biochem, São Paulo, BrazilUNIFESP, EPM, Dept Expt Neurol, São Paulo, BrazilUNIFESP, EPM, Dept Biochem, São Paulo, BrazilWeb of Scienc

Disruption of light-induced c-Fos immunoreactivity in the suprachiasmatic nuclei of chronic epileptic rats

Photic stimulation during specific day periods may induce Fos oncoprotein expression within the ventrolateral part of the suprachiasmatic nucleus (SCN) in the hypothalamus of rodents. This phenomenon appears to be a major molecular mechanism for environmental light/dark cycle entrainment of the mammalian circadian clock. Light-dependent synchronization of circadian rhythmicity may be disrupted in epilepsy, a chronic neurological disorder often associated with chronobiological features such as seizure periodicity and disruption of endogenous biological rhythms. the present work examined the light-induced Fos protein expression on the SCN in the pilocarpine model of chronic epilepsy. Fos-like immunoreactivity was significantly reduced in the SCN of chronic epileptic rats after photic stimulation during the subjective night. These results indicate an altered Fos protein expression in the SCN of chronic epileptic rats. the present findings reveal that pathological neural events underlying epileptogenesis may disturb circadian rhythm regulation. the experimental study of circadian clock activity in the SCN may clarify the molecular bases of chronobiological disturbances in epilepsy.Universidade Federal de São Paulo,ESCOLA PAULISTA MED,LAB NEUROL EXPT,BR-04023900 São Paulo,BRAZILUniversidade Federal de São Paulo,ESCOLA PAULISTA MED,LAB NEUROL EXPT,BR-04023900 São Paulo,BRAZILWeb of Scienc

Multiple pilocarpine-induced status epilepticus in developing rats: A long-term behavioral and electrophysiological study

Purpose: Animal models are useful for the study of status epilepticus (SE)-induced epileptogenesis and neurological sequelae, especially during early brain development. Here. we show several permanent abnormalities in animals subjected to multiple SE during early development.Methods: Wistar pup rats (7 to 9 days old) were subjected to three consecutive episodes of SE induced by systemic pilocarpine injections. To study the long-lasting consequences of early-induced SE, chronic electroencephalographic recordings were made from the hippocampus and cortex and several behavioral tests (inhibitory step-down avoidance, rota-rod, open field, elevated plus-maze, and Skinner box) were performed at postnatal days 30 to 90. We also investigated in vitro electrophysiological responses of the CA1 area using extracellular recordings in hippocampal slices. A histological analysis was done using cresyl violet staining 24 hours and several months after SE induction. Apoptotic cell death was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL staining) 24 hours after the last SE episode.Results: Electloencephalographic recordings from 30- to 90-day-old rats that had been subjected to multiple SE episodes in early life showed marked changes compared with those from nontreated controls. These included frequent episodes of continuous complex spiking activity and high-voltage ictal discharges, with a small percentage of these rats presenting spontaneous behavioral seizures. These animals also presented evidence of severe cognitive deficit in adulthood. in vitro, a persistent hyperexcitability of the CAI area was detected in experimental animals. Histological analysis of the brains did not reveal any major long-term pathological changes. Nevertheless, an increased number of TUNEL-positive nuclei were present in some animals in both the hippocampus and the thalamus.Conclusions: These data show persistent abnormalities in animals subjected to multiple SE episodes during early postnatal development. SE may result in important plastic changes in critical periods of brain maturation leading to long-lasting epileptogenesis, as manifested by electrogaphic epileptiform discharges, behavioral deficits, and in vitro hyperexcitability of hippocampal networks.Universidade Federal de São Paulo, Escola Paulista Med, Lab Neurol Expt, BR-04023900 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Lab Neurol Expt, BR-04023900 São Paulo, BrazilWeb of Scienc