Differential Dependency of Unmyelinated and A Delta Epidermal and Upper Dermal Innervation on Neurotrophins, Trk Receptors, and p75LNGFR

The study examined the role of neurotrophins and their receptors in the innervation of the epidermis, upper dermis, and hair follicles in mice. It was found that NGF/trkA signaling was crucial for the growth and proliferation of sensory axons, while NT-3/trkA was important for forming sensory endings. TrkC was essential for certain trkA-dependent sensory innervations, and trkB, mediated by BDNF and NT-4, suppressed some sensory and sympathetic innervations. Sympathetic innervation relied on NGF/trkA and p75, but NT-3 was detrimental to sympathetic terminations. The study highlighted a complex balance between promoting and suppressing effects of neurotrophins on innervation.