Abstract
We have developed an in vitro model of chronic epilepsy in order to study the consequences of prolonged periods of epileptic activity. After applying the convulsants bicuculline and/or picrotoxin to mature rat hippocampal slice cultures for 3 days, large numbers of swollen and vacuolated cells were observed throughout all hippocampal subfields. The number of dendritic spines of pyramidal cells was massively reduced. These changes were similar to those observed previously in post-mortem studies of hippocampal tissue from human epilepsy patients. Intracellular recordings from CA3 pyramidal cells revealed that spontaneous synaptic activity was greatly reduced in treated cultures. γ-Aminobutyric acid-mediated inhibition was apparently not affected by sustained convulsant activity, although synaptic excitation was markedly depressed. Acute re-application of bicuculline to treated cultures elicited, upon stimulation of the mossy fibre tract, a typical interictal burst lasting several hundred milliseconds, with a wave form similar to those occurring in untreated cultures, but of a shorter duration. In contrast, ictal bursts (lasting tens of seconds), which always occur spontaneously in control cultures during initial perfusion of bicuculline, were not observed in treated cultures. These pathological changes were reversible when treated cultures were returned to normal medium for 1 week. The surviving cells had a healthy morphology and a normal complement of dendritic spines. Spontaneous synaptic activity was normal, and ictal bursts occurred spontaneously upon perfusion of bicuculline. The findings suggest that the morphological and functional changes are a consequence, rather than a direct cause of epilepsy.
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References
Anderson WW, Lewis DV, Swartzwelder HS, Wilson WA (1986) Magnesium-free medium activates seizure-like events in the rat hippocampal slice. Brain Res 398:215–219
Babb TL, Wilson CL, Isokawa-Akesson M (1987) Firing patterns of human limbic neurons during stereoencephalography (SEEG) and clinical temporal lobe seizures. Electroencephalogr Clin Neurophysiol 66:467–482
Babb TL, Pretorius JK, Kupfer WR, Crandall PH (1989) Glutamate decarboxylase-immunoreactive neurons are preserved in human epileptic hippocampus J Neurosci 9:2562–2574
Caceres A, Steward O (1983) Dendritic reorganization in the denervated dentate gyrus of the rat following entorhinal cortical lesions: a Golgi and electron microscopic analysis. J Comp Neurol 214:387–403
Calverley RKS, Jones DG (1990) Contributions of dendritic spines and perforated synapses to synaptic plasticity. Brain Res Brain Res Rev 15:215–249
Choi DW, Rothman SM (1990) The role of glutamate neurotoxicity in hypoxic-ischemic neuronal death. Annu Rev Neurosci 13:171–182
Corsellis JAN, Bruton CJ (1983) Neuropathology of status epilepticus in humans. Adv Neurol 34:129–139
Davies CH, Davies SN, Collingridge GL (1990) Paired-pulse depression of monosynaptic GABA-mediated inhibitory postsynaptic responses in rat hippocampus. J Physiol (Lond) 424:513–531
Delgado-Escueta AV, Ward AA Jr, Woodbury DM, Porter RJ (1986) New wave of research in the epilepsies. Adv Neurol 44:3–55
Dichter M, Ayala G (1987) Cellular mechanisms of epilepsy: a status report. Science 237:157–164
Engel J Jr (1987) Surgical treatment of the epilepsies. Raven Press, New York
Franck JE, Kunkel DD, Baskin DG, Schwartzkroin PA (1988) Inhibition in kainate-lesioned hyperexcitable hippocampi: physiologic, autoradiographic, and immunocytochemical observations. J Neurosci 8:1991–2002
Frotscher M, Gähwiler BH (1988) Synaptic organization of intracellularly stained CA3 pyramidal neurons in slice cultures of rat hippocampus. Neuroscience 24:541–551
Gähwiler BH (1981) Organotypic monolayer cultures of nervous tissue. J Neurosci Methods 4:329–342
Gähwiler BH (1984) Slice cultures of cerebellar, hippocampal and hypothalamic tissue. Experientia 40:235–243
Geinisman Y, Morrell F, Toldo-Morrell L de (1990) Increase in the relative proportion of perforated axospinous synapses following hippocampal kindling is specific for the synaptic field of stimulated axons. Brain Res 507:325–331
Green RC, Blume HW, Kupferschmid SB (1989) Alterations of hippocampal acetylcholinesterase in human temporal lobe epilepsy. Ann Neurol 26:347–351
Holmes GL (1991) Do seizures cause brain damage? Epilepsia 37:S14-S28
Isokawa M, Levesque F (1991) Increased NMDA responses and dendritic degeneration in human epileptic hippocampal neurons in slices. Neurosci Lett 132:212–216
Isokawa-Akesson M, Wilson CL, Babb TL (1989) Inhibition in synchronously firing human hippocampal neurons. Epilepsy Res 3:236–247
Kamphuis W, Wadman WJ, Buijs RM, Lopes da Suva FH (1986) Decrease in number of hippocampal gamma-aminobutyric acid (GABA) immunoreactive cells in the rat kindling model of epilepsy. Exp Brain Res 64:491–495
Kapur J, Stringer JL, Lothman EW (1989) Evidence that repetitive seizures in the hippocampus cause a lasting reduction of GABAergic inhibition. J Neurophysiol 61:417–426
Lloyd KGH, Bossi L, Morselli PL, Munari C, Rougier M, Loiseau H (1986) Alterations of GABA-mediated synaptic transmission in human epilepsy. Adv Neurol 44:1033–1044
Mattson MP, Dou P, Kater SB (1988) Outgrowth-regulating actions of glutamate in isolated hippocampal pyramidal neurons. J Neurosci 8:2087–2100
McDonald JW, Garofalo EA, Hood T, Sackellares JC, Gilman S, McKeever PE, Troncoso JC, Johnston MV (1991) Altered excitatory and inhibitory amino acid receptor binding in hippocampus of patients with temporal lobe epilepsy. Ann Neurol 29:529–541
Meldrum BS (1985) Possible therapeutic applications of antagonists of excitatory amino acid neurotransmitters. Clin Sci 68:113–122
Meldrum BS, Corsellis JAN (1984) Epilepsy. In: Adams JH, Corsellis JAN, Duchen LW (eds) Greenfield's neuropathology. Wiley, New York, pp 921–950
Müller M, Gähwiler BH, Rietschin L, Thompson SM (1993) Reversible loss of dendritic spines and altered excitability following chronic epilepsy in hippocampal slice cultures. Proc Natl Acad Sci USA (in press)
Paul LA, Scheibel AB (1986) Structural substrate of epilepsy. Adv Neurol 44:775–786
Popov VI, Bocharova LS, Bragin AG (1992) Repeated changes of dendritic morphology in the hippocampus of ground squirrels in the course of hibernation. Neuroscience 48:45–51
Ribak CE, Bradburne RM, Harris AB (1982) A preferential loss of GABAergic symmetric synapses in epileptic foci: a quantitative ultrastructural analysis of monkey neocortex. J Neurosci 2:1725–1735
Scheibel ME, Crandall PH, Scheibel AB (1974) The hippocampal-dentate complex in temporal lobe epilepsy. Epilepsia 15:55–80
Sherwin AL, Gelder MN van (1986) Amino acid and catecholamine markers of metabolic abnormalities in human focal epilepsy. Adv Neurol 4:1011–1032
Sloviter RS (1987) Decreased hippocampal inhibition and a selective loss of interneurons in experimental epilepsy. Science 235:73–76
Sloviter RS (1991) Permanently altered hippocampal structure, excitability, and inhibition after experimental status epilepticus in the rat: the “dormant basket cell” hypothesis and its possible relevance to temporal lobe epilepsy. Hippocampus 1:41–66
Stelzer A, Slater NT, Bruggencate G ten (1987) Activation of NMDA receptors blocks GABAergic inhibition in an in vitro model of epilepsy. Nature 326:698–701
Streit P, Thompson SM, Gähwiler BH (1989) Anatomical and physiological properties of GABAergic neurotransmission in organotypic slice cultures of rat hippocampus. Eur J Neurosci 1:603–615
Thompson SM, Gähwiler BH (1992) Comparison of the actions of baclofen at pre- and postsynaptic receptors in the rat hippocampus in vitro. J Physiol (Lond) 451:329–345
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Müller, M. Morphological and functional consequences of chronic epilepsy in rat hippocampal slice cultures. Pflügers Arch. 422, 418–423 (1993). https://doi.org/10.1007/BF00374304
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DOI: https://doi.org/10.1007/BF00374304