The long term effect of repeated pluckings on the function of the mouse vibrissal follicles

Single mouse vibrissae were plucked repeatedly at the same time of the cycle (10--15 days after eruption) for ten successive cycles from eight individual follicles. After three pluckings the first grey whisker appeared, after six pluckings all were grey. Two follicles stopped producing whiskers after seven pluckings and another two after the 8th. Henceforth only 50% of the follicles continued producing whiskers until the end of the experiment. All the follicles which ceased to produce whiskers had a keratogenous cyst occupying most of the follicle in direct contact with the dermal papilla. In all cases the isolated dermal papilla was condensed and rounded in shape. Both loss of pigment and cyst formation could be due to the mechanical damage in the follicle caused by repeated plucking.