Brain regional amino acid levels in seizure susceptible rats: Changes related to sound-induced seizures.
Regional brain amino acid levels have been determined by HPLC, following microwave fixation, in seizure susceptible (University of Arizona, Audiogenic seizure-susceptible, AGS) and non-seizure susceptible Sprague-Dawley rats. Glutamine content is significantly lower in cerebellum, hippocampus, striatum, substantia nigra, colliculi and brain stem reticular formation in AGS rats. Aspartate levels are also reduced (by 33%) in striatum, substantia nigra and inferior colliculus, and glutamate is reduced in hippocampus and striatum. Other differences include a slight fall in taurine content (in striatum) and an increase in GABA content (in hippocampus). Measurements of amino acid levels in AGS rats during the course of a seizure induced by sound show increases in aspartate and glutamate content in some brain regions (including the inferior colliculus). Potassium-evoked [(3)H] d-aspartate release from hippocampal slices did not differ between the seizure-susceptible and seizure-resistant rat strains. It is proposed (i) that changes in the level and turnover of excitatory amino acid transmitters in AGS rats occur as a consequence of a primary biochemical defect that probably involves impaired neuronal membrane transport, and (ii) that altered function in excitatory synapses in the inferior colliculus, substantia nigra and reticular formation contributes importantly to the seizure susceptibility.
Chapman
A G
AG
Department of Neurology, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, England.
Faingold
C L
CL
Hart
G P
GP
Bowker
H M
HM
Meldrum
B S
BS