Characterization of voltage-and Ca2+-activated K+ channels in rat dorsal root ganglion neurons

✍ Scribed by Wei Li; Shang-Bang Gao; Cai-Xia Lv; Ying Wu; Zhao-Hua Guo; Jiu-Ping Ding; Tao Xu

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 417 KB
• Volume: 212
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.21007

✦ Synopsis

Abstract

Auxiliary β‐subunits associated with pore‐forming Slo1 α‐subunits play an essential role in regulating functional properties of large‐conductance, voltage‐ and Ca^2+^‐activated K^+^ channels commonly termed BK channels. Even though both noninactivating and inactivating BK channels are thought to be regulated by β‐subunits (β1, β2, β3, or β4), the molecular determinants underlying inactivating BK channels in native cells have not been extensively demonstrated. In this study, rβ2 (but not rβ3‐subunit) was identified as a molecular component in rat lumbar L4‐6 dorsal root ganglia (DRG) by RT‐PCR responsible for inactivating large‐conductance Ca^2+^‐dependent K^+^ currents (BK~i~ currents) in small sensory neurons. The properties of native BK~i~ currents obtained from both whole‐cell and inside‐out patches are very similar to inactivating BK channels produced by co‐expressing mSlo1 α‐ and hβ2‐subunits in Xenopus oocytes. Intracellular application of 0.5 mg/ml trypsin removes inactivation of BK~i~ channels, and the specific blockers of BK channels, charybdotoxin (ChTX) and iberiotoxin (IbTX), inhibit these BK~i~ currents. Single BK~i~ channel currents derived from inside‐out patches revealed that one BK~i~ channel contained three rβ2‐subunits (on average), with a single‐channel conductance about 217 pS under 160 K^+^ symmetrical recording conditions. Blockade of BK~i~ channels by 100 nM IbTX augmented firing frequency, broadened action potential waveform and reduced after‐hyperpolarization. We propose that the BK~i~ channels in small diameter DRG sensory neurons might play an important role in regulating nociceptive input to the central nervous system (CNS). J. Cell. Physiol. 212: 348–357, 2007. © 2007 Wiley‐Liss, Inc.