Effect of long-term administration of melatonin on adrenal histomorphology of the Indian desert gerbil Meriones hurrianae Jerdon.

Melatonin treatment for 8 weeks resulted in a significant increase (P < 0.01) in weights of the adrenal glands, in both male and female, M. hurrianae. The weight increase was not related to the time of administration of melatonin. Histology of adrenal glands in melatonin treated gerbils revealed a stimulatory response. In treated gerbils, adrenal cortex exhibited significant hypertrophy with enlarged nuclei and degranulated cytoplasm. Signs of hypertrophy were also evident in the adrenal medulla. The physiological significance of this response is not yet clear. It remains to be clarified if the hypertrophy indicates enhanced synthesis of corticosteroids.