Melatonin secretion profile after experimental pineal gland compression in rats.

OBJECTIVES Pineal gland hormone, melatonin, is a current issue of interest for accumulating data concerning its diverse physiological functions. The disturbances in melatonin secretion are observed in different pathological conditions involving pineal regions, but it is not ascertained if those disturbances present any clinical implications. The aim of this work was to examine whether pineal gland compression changes melatonin secretion. SETTING AND DESIGN The experiment was carried out on adult rats, divided into four equal groups: (i) control (no surgery was performed), (ii) sham-operated, (iii) with sham pineal gland compression and (iv) with pineal gland compression performed by cotton piece application. METHODS The profile of melatonin secretion was assessed in blood samples collected five times daily, every second day, starting from 8 to 14 day following surgery. RESULTS We found that surgery itself significantly increased night melatonin secretion in comparison to controls. By contrast, in pineal-gland compressed rats, melatonin secretion was lower than in control group, suggesting that the influence of pineal compression overcame that induced by operation stress. CONCLUSIONS In conclusion, we presume that pineal gland compression (like in case of some tumors) results in decrease of the concentration of blood melatonin, that may possibly result in decreased protective action of the indoleamine.