title: Chronic stimulation of GABAA receptor with muscimol reduces amyloid beta protein (25-35)-induced neurotoxicity in cultured rat cortical cells.
abstract: The present study was performed to examine how the stimulation of gamma-aminobutyric acid (GABA) receptor affects amyloid beta protein (25-35) (Abeta (25-35)), a synthetic 25-35 amyloid peptide, -induced neurotoxicity using cultured rat cortical neurons. Abeta (25-35) produced a concentration-dependent reduction of cell viability, which was significantly reduced by (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK-801), an N-methyl-d-aspartate (NMDA) receptor antagonist, verapamil, an L-type Ca(2+) channel blocker, and N(G)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor. Pretreatment with muscimol, a GABAA receptor agonist, over a concentration range of 0.1-10microM 24h before the treatment with 10microM Abeta (25-35) showed concentration-dependent inhibition on the Abeta (25-35)-induced neuronal apoptotic death. However, baclofen (1 and 10microM), a GABAB receptor agonist, failed to inhibit the Abeta (25-35)-induced neuronal death. In addition, pretreatment with muscimol (1microM) for 24h inhibited the Abeta (25-35) (10microM)-induced elevation of cytosolic Ca(2+) concentration ([Ca(2+)]c) and glutamate release, generation of reactive oxygen species (ROS), and caspase-3 activity in cultured neurons. These neuroprotective effects of muscimol (1microM) were completely blocked by the simultaneous treatment with 10microM bicuculline, a GABAA receptor antagonist, indicating that the protective effects of muscimol were due to GABAA receptor stimulation. When, however, treated just 15min before the treatment with Abeta (25-35), muscimol (1microM) did not show any protective effect against Abeta (25-35) (10microM)-induced neurotoxicity in cultured neurons. These results suggest that the chronic activation of GABAA receptor may ameliorate Abeta-induced neurotoxicity by interfering with the increase of [Ca(2+)]c, and then by inhibiting glutamate release, generation of ROS and caspase-3 activity.
authors.affiliation: College of Veterinary Medicine and Research Institute of Herbal Medicine, Chungbuk National University, 12 Gaesin-dong, Heungduk-Gu, Cheongju, Chungbuk 361-763, Republic of Korea.
authors.forename: Bo Young
authors.initials: BY
authors.lastname: Lee
authors.forename: Ju Yeon
authors.initials: JY
authors.lastname: Ban
authors.forename: Yeon Hee
authors.initials: YH
authors.lastname: Seong
mesh_terms: D016229:Amyloid beta-Peptides / Q000633:toxicity*; D000704:Analysis of Variance; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology*; D018698:Glutamic Acid / Q000032:analysis; D009118:Muscimol / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010446:Peptide Fragments / Q000633:toxicity*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D011963:Receptors, GABA-A / Q000502:physiology*; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D016229:Amyloid beta-Peptides; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D018755:GABA Agonists; D018696:Neuroprotective Agents; D010446:Peptide Fragments; D017382:Reactive Oxygen Species; D011963:Receptors, GABA-A; D013778:Tetrazolium Salts; D013844:Thiazoles; C074636:amyloid beta-protein (25-35); D009118:Muscimol; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D014700:Verapamil; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue; D001418:Baclofen; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester