Characterization of cyclothiazide-enhanced kainate excitotoxicity in rat hippocampal cultures.
Cyclothiazide has been shown to block desensitization of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-preferring receptors and to enhance quisqualate-, AMPA- and kainate-induced neurotoxicity. The pharmacology behind this cyclothiazide-enhanced kainate-induced excitotoxicity was characterized in embryonic rat hippocampal cell cultures. Treatment of cell cultures with a combination of cyclothiazide and kainate for 24 h resulted in excessive neuronal death as measured by the release of lactate dehydrogenase into the culture media. Cyclothiazide produced a leftward shift of the kainate dose-response curve and enhanced the maximum response of kainate excitotoxicity. AMPA-preferring receptor antagonists, 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline(NBQX) and 1-(4-amino-phenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466) blocked cyclothiazide-enhanced kainate toxicity completely, and cyclothiazide increased the IC50S for NBQX and GYKI 52466 against kainate toxicity. The N-methyl-D-aspartate (NMDA) antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK801) also blocked cyclothiazide-enhanced kainate toxicity, but only partially. Cyclothiazide also increased the IC50 for MK801 against kainate toxicity. These data suggest that cyclothiazide enhances both AMPA-preferring receptor- and NMDA receptor-mediated toxicity in kainate-induced toxicity in embryonic rat hippocampal cultures.
Ohno
K
K
Neuroscience Research Pharmacology Laboratories, Yamanouchi Pharmaceutical Co. Ltd, Tsukuba, Japan. ohno@yamanouchi.co.jp
Okada
M
M
Tsutsumi
R
R
Matsumoto
N
N
Yamaguchi
T
T
D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004622:Embryo, Mammalian; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000196:embryology; D007608:Kainic Acid / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000633:toxicity
D001581:Benzothiadiazines; D018091:Receptors, AMPA; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C004639:cyclothiazide; D007608:Kainic Acid