Effect of long-term administration of melatonin on eyes and harderian glands in albino rat.

Pineal hormone melatonin is also synthesized by the ocular structures, retina and Harderian gland. The physiological significance of such production is not fully understood. Daily treatment with melatonin (25 micrograms/rat) for 8 weeks led to an increase in weight of eye balls and fluid within it (P < 0.05). Weight of the Harderian gland in the control and treated rats was not significantly different, though the histological observation revealed an increase in cell height and reduction in lumen diameter in the treated animals. Inter luminal deposits of porphyrin content appeared to be more in the Harderian glands of melatonin treated rats. The retinal tissue indicated degenerative changes in the melatonin treated rats. The results suggest melatonin's influence on level of ocular fluid, structure/function of retina and harderian gland.