ABSTRACT
Mechanosensitive (MS) channels are ion channels gated by different types of mechanical stimuli. MS channels in sensory neurons are thought to be molecular transducers for somatic sensations such as touch, pressure, proprioception and pain. Previously, we reported that two types of MS channels are present in sensory neurons. These channels are termed low threshold (LT) and high threshold (HT) MS channels based on their pressure threshold for activation. Here, we report another type of MS channel present in sensory neurons. The channel is activated by low pressure applied to a patch (threshold approximately 20 mmHg, similar to that in the LT channel). However, because this channel has a smaller single-channel conductance than that of the LT channel, the newly classified MS channel is now called a low threshold small conductance (LTSC) channel. Unlike the LT channel, which has outwardly rectifying currents, the current-voltage relationship of the LTSC is linear. The LTSC was permeable to monovalent cations and Ca2+, and reversibly blocked by gadolinium, a blocker of MS channels. Unlike the LT channel, the LTSC was sensitized by prostaglandin E2, an inflammatory mediator that is known to sensitize nociceptors to mechanical stimuli. LTSC channels were found mostly in small cultured sensory neurons. Thus, these results suggest that the LTSC is a distinct type of MS channel that is different from the LT and HT channels in sensory neurons, and that LTSCs might play a role in mediating somatosensations, including pain.
