In vitro evidence that leptin suppresses melatonin secretion during long days and stimulates its secretion during short days in seasonal breeding ewes

Seasonal effects of central leptin infusion and prolactin treatment on pituitary SOCS-3 gene expression in ewes

“…Melatonin receptors are present within the pars tuberalis and the zona tuberalis of the ovine pituitary gland (De Reviers et al 1989). Therefore, melatonin is able to transfer photoperiodic information directly to the cells of the pituitary; furthermore, leptin-melatonin interactions have been reported (Zieba et al 2007). Whether melatonin can affect leptin action on the pituitary SOCS-3 expression in sheep needs to be further investigated.…”

Role of Leptin in the Reproduction and Metabolism: Focus on Regulation by Seasonality in Animals

“…They showed that the addition of leptin to ghrelin-treated cultures increased melatonin concentrations compared to cultures supplemented with ghrelin alone during both long and short photoperiods. Although leptin decreased melatonin secretion during long days (Zieba et al, 2007), leptin and ghrelin acted synergistically to increase melatonin concentration to higher levels than in either individually-treated or untreated cultures . These findings contribute to the formation of hypotheses concerning the joint action of leptin and ghrelin in the regulation of energy homeostasis depending on photoperiod.…”

“…It has been shown that recombinant ovine leptin is able to modulate melatonin release in ovine pineal gland explants in vitro, and this effect is seasonally dependent (Zieba et al, 2007). Exogenous leptin inhibits the secretion of melatonin from pineal gland explants during LD and stimulates this process during short days (SD) (Zieba et al, 2007).…”

The Effect of Physiological and Environmental Factors on the Prolactin Profile in Seasonally Breeding Animals

“…In experiments conducted in 2006 it was proven for the first time that leptin exerts an effect on the melatonin secretion both under in vitro [57] and in vivo [58] conditions. It was observed that the day length (photoperiod) is one of the factors which modulate the effects of leptin directly in the sheep's pineal gland, with an inhibitory effect of leptin on melatonin secreted by explants of the pineal gland in the period of lengthening days.…”

“…In consequence, it was concluded that the secretion of the hormones retained its endogenous seasonal rhythm. The effect of the loss of the pituitary cells' sensitivity to the summer signal of the hormone of darkness repeating for too long does not allow for extension of sheep's lactation to the autumn and winter period [57].…”