Changes in hair growth (8)

Changes in hair growth (8)


SUMMARY
The effect on hair growth of wounding the lower region of whisker follicles, and in particular
the dermal papilla, with sharply pointed tungsten needles was studied in adult hooded rats.
Following injury hair growth ceased, but was subsequently resumed. While it might have been
anticipated that follicle wounding would have a negative effect on whisker length, regular postoperative
length measurements revealed that in follicles where cellular material was not
displaced from the follicle by the original manipulation, 50 % of the subsequent hairs produced
were longer than their counterparts on the opposite side of the face, with 25 % shorter and 25 %
with their length unchanged. In every case increased hair length was achieved by a prolongation
of the growing period of the hair. Growth rate, when altered, was reduced. These results suggest
that the factors which control the duration of the hair cycle and fibre growth rate are independent
in vibrissa follicles. Since removal of most of the epidermal component by plucking of the hair
just prior to injury produced equivalent hair length increases, this implicated the proximal
dermal components as being mainly responsible for the observed changes.