Mark V. Dahl, MD

Merkel cells actively participate in touch reception.

Epidermal Merkel cells display features of sensory receptor cells. They can make synapse-like contact with afferent nerves. A current study shows how Merkel cells participate in touch responses.

The investigators isolated murine Merkel cells and measured their internal currents. Mechanical displacement of cell membranes of Merkel cells elicited inward-directed “electrical currents.” Channels opened, and calcium ions moved quickly into the cell. Thus, they showed that Merkel cells can transduce touch stimuli into currents in the absence of sensory neurons or keratinocytes and act as sensory end organs. The Merkel cell-neurite complex has two different receptor cell types specialized for two distinct elements of discriminative touch. Merkel cells mediate two responses: (1) sustained responses with steady-state currents at about 10% of peak response and (2) high-frequency firing with intermittent currents. The investigators stimulated epidermal touch domes (concentrations of Merkel nerve endings) using laser-coupled fiber optics, which elicited high-frequency spike waveform responses and enabled sustained firing. Increased intensity of light increased frequency of firing. Steady-state firing informs the brain about pressure, high-frequency firing about object features such as edges and curves. Together, these responses inform the sense of touch with high spatiotemporal acuity.

Citation(s):

Maksimovic S et al. Epidermal Merkel cells are mechanosensory cells that tune mammalian touch receptors. Nature 2014 Apr 6; [e-pub ahead of print].