Effects of bilateral adrenalectomy on initiation of fur growth cycles in the deer mouse (Peromyscus maniculatus).

The objectives of this study were to determine the effects of bilateral adrenalectomy on the initiation of hair growth in the deer mouse and the duration of the actively growing phase of the hair growth cycle (anagen). Bilateral adrenalectomy plus deoxycorticosterone supplementation of adult deer mice resulted in the onset of hair growth 4 days earlier than in sham-operated mice supplemented with deoxycorticosterone. The duration of hair growth (anagen), based on guard hair measurements, was estimated to be approximately 12 days in both groups. As was expected for this species, the portion of the sheared test area in which new hair grew was incomplete in all control mice. In contrast, all adrenalectomized mice had hair growth over the entire sheared area. This suggests that normal, incomplete pelage replacement in adults was abolished and that adrenalectomy had a systemic effect, causing a greater number of hair follicles to become activated concurrently. These findings support the hypothesis that adrenal hormones exert an inhibitory effect on the induction of anagen and may be part of the mechanism controlling the onset of hair growth cycles.