The Cav3.2 T-type calcium channel regulates temporal coding in mouse mechanoreceptors

J Physiol. 2011 May 1;589(Pt 9):2229-43. doi: 10.1113/jphysiol.2010.203463. Epub 2011 Feb 28.

Abstract

In mammals there are three types of low-voltage-activated (LVA) calcium channels,Cav3.1, Cav3.2 and Cav3.3, which all give rise to T-type Ca2+currents. T-type Ca2+currents have long been known to be highly enriched in a sub-population of medium-sized sensory neurones in the dorsal root ganglia (DRG). However, the identity of the T-type-rich sensory neurones has remained controversial and the precise physiological role of the Cav3.2 calcium channel in these sensory neurones has not been directly addressed. Here we show, using Cav3.2−/− mutant mice,that these channels are essential for the normal temporal coding of moving stimuli by specialized skin mechanoreceptors called D-hair receptors.We show that D-hair receptors from Cav3.2−/− fire approximately 50% fewer spikes in response to ramp-and-hold displacement stimuli compared to wild type receptors. The reduced sensitivity of D-hair receptors in Cav3.2−/− mice is chiefly due to an increase in the mechanical threshold and a substantial temporal delay in the onset of high-frequency firing to moving stimuli.We examined the receptive properties of other cutaneous mechano receptors and Aδ- and C-fibre nociceptors in Cav3.2−/− mice, but found no alteration in their mechanosensitivity compared to Cav3.2+/+mice. However, C-fibre nociceptors recorded in Cav3.2−/− mutant mice displayed a small but statistically significant reduction in their spiking rate during noxious heat ramps when compared to C-fibres in control mice. The T-type calcium channel Cav3.2 is thus not only a highly specific marker of D-hair receptors but is also required to maintain their high sensitivity and above all to ensure ultra rapid temporal detection of skin movement.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Calcium Channels, T-Type / deficiency
  • Calcium Channels, T-Type / genetics
  • Calcium Channels, T-Type / metabolism*
  • Calcium Signaling*
  • Cells, Cultured
  • Ganglia, Spinal / metabolism
  • Mechanoreceptors / metabolism*
  • Mechanotransduction, Cellular*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nerve Fibers, Myelinated / metabolism
  • Nerve Fibers, Unmyelinated / metabolism
  • Physical Stimulation
  • Reaction Time
  • Sensory Thresholds
  • Skin / innervation*
  • Time Factors

Substances

  • Cacna1h protein, mouse
  • Calcium Channels, T-Type