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Neuropathological changes in the rat brain cortex in vitro effects of kainic acid and of ion substitutions



Neuropathological changes in the rat brain cortex in vitro effects of kainic acid and of ion substitutions



Brain Research 423(1-2): 213-220



The ionic mechanisms that may contribute to the neurotoxicity of kainic acid, were studied in a system of rat thin neocortical slices superfused in vitro. Slices superfused for 3 h under control conditions showed an essentially normal aspect when studied by light microscopy. Presence of 30 .mu.M kainate in the superfusion fluid induced neuronal swelling, nuclear condensation and signs of necrosis in some cells, while other neurons, especially in deeper layers, appeared dark and condensed, with microvacuolation. The neuropil presented numerous profiles of swollen dendrites. When the slices were superfused with chloride-free medium, a large number of pyknotic neurons was seen. This was further enhanced by 30 .mu.M kainate, which produced no swelling in this medium. These effects of Cl-free medium were almost entirely prevented in Cl-free medium without calcium and with 0.1 mM of EGTA. Sodium-free medium induced a marked neuronal swelling that was not much changed by kainate. When calcium in an otherwise normal superfusion fluid was reduced to 0.1 mM, a large number of pyknotic neurons, some with incrustations, were seen. Kainate (30 .mu.M) in this low calcium medium led to a very large swelling and destruction of neurons, and to a spongy neuropil. These effects of kainate were greatly intensified in calcium-free-EGTA (0.1 mM) medium. Ca-free-EGTA medium by itself induced considerable neuronal and neuropil swelling. It is concluded that kainate induces neuronal swelling by a sodium- and chloride-dependent mechanism, and the enhancement of swelling in low calcium is due to an increased sodium uptake. Neuronal pyknosis, on the other hand, is induced by seizure-inducing conditions such as Cl-free medium, kainate, 0.1 mM calcium, or 1 mM pentylenetetrazol, apparently in a calcium-dependent manner. It is postulated that neuronal condensation and pyknosis are due to a calcium-induced cytoskeletal collapse.

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Accession: 005970914

Download citation: RISBibTeXText

PMID: 3119152

DOI: 10.1016/0006-8993(87)90842-0


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