In vitro seasonal variations of LH, FSH and prolactin secretion of the male rat are dependent on the maternal pineal gland.

The maternal pineal gland is involved in the seasonal rhythms entrainment. We evaluate the effect of maternal pinealectomy (PIN-X), also melatonin replacement (PIN-X+MEL) during pregnancy on "in vitro" gonadotropins and prolactin seasonal variations. Male offspring from control, PIN-X and PIN-X+MEL mother Wistar rats were studied at 31 and 60 days of age. In vitro LH release from controls was season-dependent during prepubertal and pubertal periods showing reduced values in winter. The mother pineal gland seems to be important in the entrainment of seasonal variations of in vitro pituitary LH release, since altered secretion showing very high values was observed in summer. Melatonin treatment to PIN-X mothers partially restored the LH response. The effect of pinealectomy upon LH secretion disappears at the pubertal phase. A different pattern was observed for FSH release, without seasonal variations at 31 or at 60 days of age in control offspring, but pinealectomy to mothers or melatonin treatment resulted in seasonal variations. Seasonal influence was also observed in the prolactin pituitary release of controls. PIN-X mother offspring showed delayed seasonal variations at 31 and 60 days of age. The effect of maternal melatonin treatment during pregnancy was observed up to 60 days of age.