Specific [3H]L-glutamate binding and [3H]D-aspartate release in the hippocampus of rat after pentylenetetrazol kindling and long-term potentiation.
In the present study, the time-course of changes in glutamate binding and aspartate release in the rat hippocampus following tetanization of perforant pathway and of pentylenetetrazol-induced kindling was investigated. The K+ (48 mM)-stimulated [3H]D-aspartate release from hippocampal slices and the specific [3H]L-glutamate binding to crude synaptic membranes of the hippocampus were measured 1, 4 and 24 h after the last tetanization train or one, five and nine weeks after the last pentylenetetrazol injections, respectively. The tetanization of the fascia dentata was followed by a significant increase in K(+)-stimulated [3H]D-aspartate release from hippocampal slices only 1 h after the last tetanization train, but the specific [3H]L-glutamate binding was enhanced 4 h afterwards. No further deviations from controls have been seen 24 h after tetanization. After pentylenetetrazol kindling, the K(+)-stimulated amino acid release from hippocampal slices was not changed. However, at one week as well as at five and nine weeks after the pentylenetetrazol kindling the specific [3H]L-glutamate binding in the hippocampus was significantly increased by about 50% compared to controls. From these findings it can be assumed that after long-term potentiation induction presynaptic transmitter release and post- (and/or pre-)synaptic glutamate binding are elevated with a different time course only in the early phase of potentiation. In contrast, kindling results in a long lasting increase in activity state of glutamatergic transmission. Therefore, it can be concluded that differences of the synaptic excitability following long-term potentiation and kindling are reflected by a different activation of glutamatergic system in the central nervous system.
Schröder
H
H
Institute of Pharmacology and Toxicology, O. V. Guericke University, Magdeburg, Germany.
Schlichthaar
R
R
Krug
M
M
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007696:Kindling, Neurologic; D007700:Kinetics; D017774:Long-Term Potentiation; D008297:Male; D010433:Pentylenetetrazole / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D013997:Time Factors; D014316:Tritium
D005971:Glutamates; D014316:Tritium; D001224:Aspartic Acid; D018698:Glutamic Acid; D010433:Pentylenetetrazole