Question

Neuroscience

1. The sustained Merkel receptor complex touch response depends on activation of the ion channel Piezo2 and a complex interplay between the Merkel cells and the nerve fibers that innervate them. A) Describe how the sustained response is generated. B) Is there a way you could convert the response of Merkel receptor complex from sustained to transient by addition of an ion channel without altering Piezo2? Explain what type of channel you would add, what cell type would express it in and why it would work.

Answer 1

Piezo2, a mechanically-activated (MA) cation channel, is expressed in Merkel cells. Piezo2 is the Merkel cell mechanotransduction channel and provide the first line of evidence that Piezos play a physiological role in mechanosensation in mammals.

Tactile stimuli activate the mechanically gated ion channel Piezo2 and cause influx of cation ions, which will in turn lead to activation of voltage-gated Ca2+ channels (“VGCC”), firing of action potentials, release of neurotransmitters from synaptic vesicles (small dotted circles), and eventual generation of slowly adapting impulses in SA1 afferents. The nature of transmitters and its receptors (green) remains not fully clear. The SA1 terminals may also express Piezo2 and/or other unknown mechanically gated ion channel and their direct response to tactile stimuli could be responsible for early dynamic bursting firing that is independent of Merkel cells.