Cytotoxic action of lindane in cerebellar granule neurons is mediated by interaction with inducible GABA(B) receptors.
The cytotoxic action of the gamma-isomer of hexachlorocyclohexane (gamma-HCH, lindane) was studied in cultured mouse cerebellar granule neurons maintained in the presence or absence of the GABA(A) receptor agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol). The cells were exposed for 24 hr to lindane (30-300 microM) in the culture medium. Changes in mitochondrial function were investigated by using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) test. The results showed that lindane-induced cytotoxicity was concentration-dependent. In cerebellar granule cells not treated with THIP, lindane-induced cytotoxicity did not appear to be related to GABA(A) or GABA(B) receptors. However, in THIP-treated cultures, lindane-induced cytotoxicity was found to be mediated by an action of the insecticide on GABA receptors. In the latter case, GABA reduced the lindane-induced cytotoxicity, but the protective effect was not potentiated by flunitrazepam. The GABA(A) receptor agonist muscimol (50 microM) also protected the THIP-treated cultures against lindane-induced cytotoxicity. In addition, the GABA(B) receptor agonist R(+)baclofen protected the cells from lindane-induced cytotoxicity and the effect of baclofen was blocked by GABA(B) receptor antagonists. Pertussis toxin was found to reverse the protective effect of baclofen only at the highest lindane concentration (300 microM). The lindane-induced cytotoxicity could be partly explained as being secondary to excitotoxicity as a mixture of the excitatory amino acid receptor antagonists APV (D-(-)-2-amino-5-phosphonopentanoate) and CNQX (6-cyano-7-nitro-quinoxaline-2,3-dione) shifted the concentration-response curve for lindane-induced cytotoxicity to the right. It is suggested that the cytotoxic effects of lindane in THIP-treated cerebellar granule neurons are primarily related to an action of lindane on GABA(B) receptors and to a lesser extent on inducible low-affinity, benzodiazepine insensitive GABA(A) receptors.
Vale
C
C
Department of Neurochemistry, Institut d'Investigacions Biomèdiques de Barcelona, CSIC, Spain.
Damgaard
I
I
Suñol
C
C
Rodríguez-Farré
E
E
Schousboe
A
A
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004396:Coloring Agents; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D001556:Hexachlorocyclohexane / Q000633:toxicity*; D007306:Insecticides / Q000633:toxicity*; D007555:Isoxazoles / Q000494:pharmacology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D013778:Tetrazolium Salts; D013844:Thiazoles
D004396:Coloring Agents; D018691:Excitatory Amino Acid Antagonists; D018755:GABA Agonists; D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D007306:Insecticides; D007555:Isoxazoles; D013778:Tetrazolium Salts; D013844:Thiazoles; D001556:Hexachlorocyclohexane; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; C022616:thiazolyl blue; C015542:gaboxadol