The effect of pineal treatment and pinealectomy on prolactin in rats.

Administration of melatonin-free pineal extract in doses of 2 ml/day/animal along 3 or 7 days caused a statistically significant decrease in the rat serum prolactin level by 28 and 25% respectively, as against the controls. Pinealectomy caused a statistically significant increase in the serum prolactin level by 34% as against the intact controls and by 30% as against the sham-operated ones. The authors discuss their completely oposite results and the role of the pineal gland on prolactin.