Diminished potassium-stimulated GABA release in vivo in genetically epilepsy-prone rats.
This experiment was conducted to assess the physiological relevance of observed changes in transmitter amino acid content in severe seizure genetically epilepsy-prone rats (GEPR-9s) by use of microdialysis. Adult male GEPR-9s and non-epileptic control rats were implanted with guide cannulae, and 6 mm (loop) dialysis probes were inserted unilaterally into rostral caudate and perfused with artificial cerebrospinal fluid. Each subject was perfused in the awake state with 100 or 150 mM K+ for 80 min in separate counterbalanced sessions, and 20-min fractions collected. High K+ perfusion increased extracellular fluid GABA and glutamate (GLU) in a concentration-dependent manner in both GEPR-9s and non-epileptic control rats. However, in the presence of 150 mM K+ GABA release was decreased in GEPR-9s relative to controls throughout the stimulation interval. In contrast, the increase in extracellular fluid GLU after high K+ was not different in the two groups. These results suggest an important role for mechanisms underlying GABA release in the seizure susceptibility observed in GEPR-9s.
Department of Basic Sciences, University of Illinois College of Medicine at Peoria 61656.
S M
SM
Lasley
Q S
QS
Yan
D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004827:Epilepsy / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D007700:Kinetics; D008297:Male; D017551:Microdialysis / Q000295:instrumentation / Q000379:methods; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D011188:Potassium