Age-related changes of inactivating BK channels in rat dorsal root ganglion neurons.

The large-conductance, voltage- and Ca(2+)-activated K(+) channels (termed BK) are associated with age-related dysfunctions or diseases. Previously, with our colleagues, we reported that the rβ2-associated inactivating BK (BKi) channels play an essential role in rat dorsal root ganglion (DRG) neurons. However, the age-dependent changes in BKi channels are still elusive. Here, we identify three types of BK channels in small DRG neurons, the single exponential BKi, the double exponential BKi and the non-inactivating BK. Interestingly, compared to the increased occurrence of the non-inactivating BK, the presence of BKi channels declined with age. Furthermore, the peak amplitude of the single exponential BKi current increased from infancy to youth, but decreased from youth to old age. The inactivation time constant, however, did not change with age. The double exponential BKi also displayed age-related change in current amplitude with an intricate kinetics. Physiologically, the decay speed of the action potential was significantly increased in Youth, which correlated with the change of current amplitude of BKi channels. Collectively, these results reveal an age-related change pattern of BKi channels in small DRG neurons, providing potential mechanistic clues for different susceptibility to sensation in different ages.