Contrasting roles of protein kinase C in induction versus suppression of group I mGluR-mediated epileptogenesis in vitro.
Activation of group I metabotropic glutamate receptors (mGluRs) elicits persistent ictaform discharges in guinea pig hippocampal slices, providing an in vitro model of epileptogenesis. The induction of these persistent ictaform bursts is prevented by l-cysteine sulfinic acid (CSA), an agonist at phospholipase D (PLD)-coupled mGluRs. Studies described herein examined the role of protein kinase C (PKC) in both the group I mGluR-mediated induction and CSA-mediated suppression of this form of epileptogenesis. Intracellular recordings were performed from CA3 stratum pyramidale and synchronized burst length was monitored. In the presence of 50 microM picrotoxin, a gamma-aminobutyric acid type A antagonist, 250- to 500-ms synchronized bursts were elicited. (S)-3,5-Dihydroxyphenylglycine (DHPG, 50 microM), an agonist at group I mGluRs, increased the burst length to 1-3 s in duration, a change that persisted after agonist washout. This persistent change in burst length was elicited in the presence of 10 microM chelerythrine, a PKC inhibitor, indicating that DHPG-induced epileptogenesis is PKC independent. However, although PLD activation with CSA (100 microM) was highly effective at suppressing group I mGluR-mediated induction of burst prolongation, CSA application in the presence of chelerythrine was no longer effective and resulted in the expression of persistent ictaform bursts. These data suggest that CSA-mediated suppression of group I mGluR-induced epileptogenesis is PKC dependent. We propose that CSA mediates its effect by PLD-driven activation of PKC, which may desensitize the phospholipase C-linked group I mGluRs and thereby prevent group I mGluR-induced epileptogenesis.
Cuellar
John C
JC
Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Box 29, Brooklyn, NY 11203, USA.
Griffith
Elvin L
EL
Merlin
Lisa R
LR
D000200:Action Potentials; D001683:Biological Clocks; D002478:Cells, Cultured; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004827:Epilepsy / Q000503:physiopathology*; D006624:Hippocampus / Q000187:drug effects / Q000503:physiopathology*; D009473:Neuronal Plasticity; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*
D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D003545:Cysteine; C013461:cysteine sulfinic acid