Involvement of substance P and the neurokinin-1 receptor in radiation-induced hair loss in mice.

We investigated the involvement of substance P (SP) and the neurokinin-1 receptor (NK(1)R) in the development of radiation-induced hair loss in mice. A dose of 40 Gy of gamma irradiation induced hair loss from the 10th to at least the 60th day after irradiation. A specific NK(1)R antagonist, CP-99,994, significantly delayed radiation-induced hair loss and reduced its severity. Furthermore, gamma irradiation induced the expression of preprotachykinin-A, a precursor protein of SP, mRNA in irradiated murine skin on the 10th and 30th days after irradiation. These results indicated that gamma irradiation-induced hair loss was mediated by SP via NK(1)R.