Effects of intracranial surgery on pineal lipid droplets, on other structures, and on melatonin secretion

Unique effects of sham-pinealectomy [intracranial surgery (IS)] which include reduced functional activity of the adrenal gland and suppressed circadian rhythms of the adrenal medulla, and which are reversed by pinealectomy, have been reported in rodents. To clarify the mechanisms, we investigated whether or what changes occur in pineal functional activity after IS. Sixty-six male rats of normal and IS groups were used at 50 days of age. The pineal gland was first examined by quantitative electron microscopy. The Sudan III-stained lipid droplet content of the pinealocytes and plasma melatonin level were then investigated using the same animals. In IS rats, the lipid droplet content of the pinealocytes decreased in both the dark and light phases 14 days after surgery. Mean volumetric ratio of nucleus, nucleolus, and mitochondria tended to increase in IS rats. The mean plasma concentration of melatonin showed apparent day–night changes, but no significant changes because of IS, 36 h and 14 days after surgery. But in the dark phase 14 days after surgery, plasma melatonin levels showed increased dispersion of values ( P