Pineal effects on adrenal medulla, area postrema and brain water content in relation to intracranial surgery

We aimed to explore whether and how the pineal influences the adrenal medulla, the area postrema and the brain water content; and is influenced by sham pinealectomy (SPX) in its structures and melatonin secretion. Quantitative morphological methods were mainly used in rats and golden hamsters. Experimental results showed: (1) Pineal effects on the A cell system of the adrenal medulla were inhibitory to the synthesis and secretion of epinephrine into the perivascular space and stimulatory to the opioid synthesis, and augmented by SPX. Time-of-day changes were also influenced by SPX and PX. (2) The sizes of a part of the nuclei of nerve and glia cells in the area postrema and the brain water content increased by SPX depending on the presence of the pineal, suggesting the pineal's stimulatory effects on these following SPX. (3) SPX caused morphological changes suggesting an increased activity of pinealocytes. However, corresponding consistent increases in plasma melatonin levels were not seen following SPX. Possible interpretations of these observations were discussed.