title: BK channels reveal novel phosphate sensitivity in SNr neurons.
abstract: Whether large conductance Ca(2+)-activated potassium (BK) channels are present in the substantia nigra pars reticulata (SNr) is a matter of debate. Using the patch-clamp technique, we examined the functional expression of BK channels in neurons of the SNr and showed that the channels were activated or inhibited by internal high-energy phosphates (IHEPs) at positive and negative membrane potentials, respectively. SNr neurons showed membrane potential hyperpolarization under glucose-deprivation conditions which was attenuated by paxilline, a specific BK channel blocker. In addition, Fluo-3 fluorescence recording detected an increase in the level of internal free calcium ([Ca(2+)](i)) during ischemic hyperpolarization. These results confirm that BK channels are present in SNr neurons and indicate that their unique IHEP sensitivity is requisite in neuronal ischemic responses. Bearing in mind that the K(ATP) channel blocker tolbutamide also attenuated the hyperpolarization, we suggest that BK channels may play a protective role in the basal ganglia by modulating the excitability of SNr neurons along with K(ATP) channels under ischemic stresses.
authors.affiliation: State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China. jijj@ibp.ac.cn
authors.forename: Juan Juan
authors.initials: JJ
authors.lastname: Ji
authors.forename: Lianwan
authors.initials: L
authors.lastname: Chen
authors.forename: Xuezhi
authors.initials: X
authors.lastname: Duan
authors.forename: Xueqin
authors.initials: X
authors.lastname: Song
authors.forename: Wenting
authors.initials: W
authors.lastname: Su
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Shuyun
authors.initials: S
authors.lastname: Bai
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Sun
authors.forename: Nobuya
authors.initials: N
authors.lastname: Inagaki
mesh_terms: D000818:Animals; D007211:Indoles / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D013378:Substantia Nigra / Q000166:cytology*
chemical_list: D007211:Indoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010710:Phosphates; C048220:paxilline