Glutamate receptor antagonists and benzodiazepine inhibit the progression of granule cell dispersion in a mouse model of mesial temporal lobe epilepsy.
OBJECTIVE
Unilateral intrahippocampal injection of kainic acid (KA) in adult mice induces the progressive dispersion of dentate granule cells, one of the characteristic pathologic changes of mesial temporal lobe epilepsy. However, little is known about the mechanisms that trigger this dispersion. In this study, the possible involvement of glutamatergic and gamma-aminobutyric acid (GABA)ergic neurotransmissions in the development of granule cell dispersion (GCD) was examined in this model.


METHODS
Antagonists of N-methyl-d-aspartate (NMDA) receptor (MK-801) and non-NMDA receptor (GYKI52466), and an agonist of benzodiazepine-GABA(A) receptor (midazolam) were injected before and after KA in various ways, and the morphologic changes of the hippocampus, especially GCD, were examined.


RESULTS
MK-801 (5 mg/kg, i.p.) did not reduce GCD when injected 2 h before KA injection but inhibited GCD almost completely for <or=14 days, when injected 4 h after KA. However, mild to moderate dispersion was observed at 28 days, indicating that MK-801 may delay the progression of GCD. Similarly, daily treatment with MK-801 (2 x 1 mg/kg i.p./day) for the first 26 days after KA significantly reduced GCD. In contrast, GYKI52466 (30 mg/kg, s.c.) was effective only when it was injected before KA. A significant reduction of GCD was also observed after continuous administration of midazolam (10 mg/kg/h) after KA.


CONCLUSIONS
These data show that GCD in this mouse model is triggered by either the stimulation of the NMDA receptor or reduction of GABA(A)-mediated inhibition after intrahippocampal injection of KA. It is suggested that the increased excitation or the reduced inhibition or both could be one of the factors triggering or maintaining or both the process of GCD.
Suzuki
Fumio
F
Department of Neurosurgery, Shiga University of Medical Science, Ohtsu, Japan. fsuzuki@belle.shiga-med.ac.jp
Heinrich
Christophe
C
Boehrer
Any
A
Mitsuya
Koichi
K
Kurokawa
Kiyoshi
K
Matsuda
Masayuki
M
Depaulis
Antoine
A
D000818:Animals; D001569:Benzodiazepines / Q000494:pharmacology*; D002452:Cell Count; D018891:Dentate Gyrus / Q000187:drug effects / Q000473:pathology; D004195:Disease Models, Animal; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000473:pathology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D018757:GABA Modulators / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects* / Q000473:pathology; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008874:Midazolam / Q000494:pharmacology; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects
D018691:Excitatory Amino Acid Antagonists; D018757:GABA Modulators; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; C061950:GYKI 52466; D001569:Benzodiazepines; D016291:Dizocilpine Maleate; D008874:Midazolam; D007608:Kainic Acid