Seasonality of prolactin in birds and mammals

Abstract

In most animals, annual rhythms in environmental cues and internal programs regulate seasonal physiology and behavior. Prolactin, an evolutionarily ancient hormone, serves as a molecular correlate of seasonal timing in most species.Prolactin is highly pleiotropic with a wide variety of well-documented physiological effects; in a seasonal context prolactin is known to regulate annual changes in pelage and molt. While short-term homeostatic variation of prolactin secretion is under the control of the hypothalamus, long-term seasonal rhythms of prolactin are programmed by endogenous timers that reside in the pituitary gland. The molecular basis of these rhythms is generally understood to be melatonin dependent in mammals. Prolactin rhythmicity persists for several years in many species, in the absence of hypothalamic signaling. Such evidence in mammals has supported the hypothesis that seasonal rhythms in prolactin derive from an endogenous timer within the pituitary gland that is entrained by external photoperiod. In this review, we describe the conserved nature of prolactin signaling in birds and mammals and highlight its role in regulating multiple diverse physiological systems. The review will cover the current understanding of the molecular control of prolactin seasonality and propose a mechanism by which longterm rhythms may be generated in amniotes.

Prolactin Mediates Long-Term, Seasonal Rheostatic Regulation of Body Mass in Female Mammals

“…Prolactin secretion from the pituitary gland provides an evolutionary conserved output signal for the neuroendocrine control of seasonal physiology ( 29 ). Across seasonally breeding animals there is increased secretion of prolactin during periods of breeding and high energy demands.…”

“…Prolactin is an evolutionarily conserved hormone produced in the pituitary gland that impacts a multitude of neuroendocrine systems ( 28 , 29 ). Of relevance, prolactin regulates longer-term changes in energy homeostasis during pregnancy and lactation ( 30 ).…”

Impact of high-fat diet and exposure to constant light on reproductive competence of female ICR mice

“…In mammals, levels of prolactin production also exhibit a seasonal response based on photoperiod. During short day photoperiods, prolactin secretion is suppressed relative to long day photoperiods across multiple species to include dairy cattle ( Auchtung et al, 2005 ), rodents and sheep ( Stewart and Marshall, 2022 ; Dodge and Badura, 2001 , 2002 ). We interpret the elevated prolactin levels in the continuous light treatments as a response to the overall amount of light, as opposed to circadian disrupting effects ( Lincoln et al, 2003 ; Dardente, 2007 ).…”

Prolactin Expression in the Baboon (Papio hamadryas) Eye

“…PRL gene has 5 exons and 4 introns, and is located on chromosome 6 [ 2 ]. PRL is an evolutionarily ancient hormone, that serves as a molecular correlate of seasonal timing in most species [ 3 ]. PRL belongs to a gene family that comprises PRL, growth hormone, and somatolactin [ 4 ].…”