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Journal of Chemical Neuroanatomy Jul 2020Seasonal reproduction is common across temperate zone avian species. In these species, physiological and behavioral adaptations have evolved to change according to day...
Seasonal reproduction is common across temperate zone avian species. In these species, physiological and behavioral adaptations have evolved to change according to day length (i.e., seasonally) in order to maximize reproductive output. The hormone prolactin regulates many aspects of parental care, a critical component of reproductive success. It's secretion in birds has been shown to be under photoperiodic control, with the highest levels measured in the spring and summer months, when birds breed and show parental care. However, to date, no study has tested whether the densities of central prolactin binding sites vary seasonally, which may also account for prolactin's effect on parental care. To test this, we collected brains from free-ranging adult male dark-eyed juncos, Junco hyemalis, a biparental songbird, in the spring, summer, and fall, and used quantitative in vitro autoradiography to compare the densities of specific prolactin binding sites across 20 different brain regions. Prolactin binding sites were found in regions that regulate parental behavior in other avian species. During the summer, several hypothalamic regions that regulate parental care, including the preoptic area and tuberal nucleus, contained lower densities of prolactin binding sites, suggesting exposure to higher endogenous prolactin levels, than at other times. This observation is consistent with the fact that circulating prolactin is highest during summer, when males would be providing care to young. Overall, these data suggest that prolactin binding sites are relatively conserved in the avian brain and that central prolactin activity supports parental care efforts in juncos and other avian species.
Topics: Animals; Binding Sites; Brain; Hypothalamus; Male; Passeriformes; Photoperiod; Prolactin; Receptors, Prolactin; Reproduction; Seasons
PubMed: 32278635
DOI: 10.1016/j.jchemneu.2020.101786 -
Pathologie-biologie Feb 1975Prolactin has a cocarcinogenic activity in the rat and mouse as its administration or stimulation of endogenous secretion increases the incidence and reduces the latent... (Review)
Review
Prolactin has a cocarcinogenic activity in the rat and mouse as its administration or stimulation of endogenous secretion increases the incidence and reduces the latent period of breast tumours, whether spontaneous or induced by chemical carcinogens. Prolonged hyperprolactinemia obtained by neutralizing the inhibitory influence of the hypothalamus on its secretion and liberation, favours the development of breast carcinoma and inversely. (Estrogens and prolactin exert a synergistic effect, both centrally and peripherally, on the acinar cells of the breast. Prolactin dependency of these mammary carcinomas is due to the persistence of specific cell receptors. In human pathology, it has not yet been possible to demonstrate a comparable effect of prolactin. Radioimmunoassay of plasma prolactin and specific receptors, together with epidemiological enquiries, should rapidly confirm or refute the cocarcinogenic effect of prolactin.
Topics: Animals; Breast Neoplasms; Carcinogens; Cell Membrane; Drug Synergism; Estrogens; Humans; Hypothalamus; Mammary Neoplasms, Experimental; Mice; Prolactin; Radioimmunoassay; Rats; Receptors, Cell Surface
PubMed: 165449
DOI: No ID Found -
Schweizerische Rundschau Fur Medizin... Mar 1977
Topics: Bromocriptine; Dopamine; Female; Galactorrhea; Humans; Male; Pregnancy; Prolactin; Thyrotropin-Releasing Hormone; Tranquilizing Agents
PubMed: 403518
DOI: No ID Found -
Life Sciences Aug 1974
Review
Topics: Circadian Rhythm; Female; Humans; Hypothalamus; Menstrual Cycle; Prolactin
PubMed: 4620965
DOI: 10.1016/0024-3205(74)90501-3 -
International Review of Cytology 1985Is the entry hypothesis compatible with all the existing data about "the" second messenger for prolactin listed in Section II? All of these messengers, in some way... (Review)
Review
Is the entry hypothesis compatible with all the existing data about "the" second messenger for prolactin listed in Section II? All of these messengers, in some way either participate in, or modify, prolactin's actions or, in an end point-dependent manner, may actually mimic prolactin. There remains considerable uncertainty as to whether these findings reflect phenomena, some independent of and others quite dependent upon entry, on the one hand, or merely portions of a relatively large number of molecular cascades, some (but not necessarily all) begun initially at the plasmalemma and many (if not all) orchestrated toward completion by intracellular prolactin or agonist-receptor complex.
Topics: Animals; Cytoskeleton; Humans; Lysosomes; Models, Biological; Pituitary Gland, Anterior; Prolactin; Receptors, Cell Surface; Receptors, Prolactin
PubMed: 2997071
DOI: 10.1016/s0074-7696(08)60578-1 -
Ciba Foundation Symposium 1992We have investigated the mechanisms involved in the inhibition by dopamine of the transformation of prolactin within the anterior pituitary of the lactating rat. The... (Review)
Review
We have investigated the mechanisms involved in the inhibition by dopamine of the transformation of prolactin within the anterior pituitary of the lactating rat. The degree of inhibition depends on the intracellular age of prolactin, being greater in newly synthesized (<1 hour) and in older (>12 hours since biosynthesis) hormone and lesser in prolactin synthesized 4-8 hours earlier. Transformation occurs in prolactin granules and involves an increase in oligomeric forms of prolactin at the expense of the monomeric form. A reversible disulphide-linked mechanism may be involved in dopamine inhibition of prolactin transformation; it is dependent upon the intracellular and/or intragranular pH via a Na+/H+ exchange mechanism. Transient suppression of dopamine inhibition may lower the intracellular/intragranular pH and subsequently cause transformation of the hormone. Developmentally, dopamine secretion by tuberoinfundibular neurons is seriously impaired and the response of pituitary lactotrophs to dopamine is reduced in adult rats deprived of milk prolactin during Days 2-5 post partum. These results suggest milk prolactin ingested during a critical post partum period may exert an organizational effect upon dopamine secretion and its function on the pituitary lactotroph during adulthood.
Topics: Animals; Animals, Newborn; Female; Homeostasis; Lactation; Pituitary Gland, Anterior; Prolactin; Rats
PubMed: 1425029
DOI: 10.1002/9780470514283.ch6 -
Hormones and Behavior Oct 2009Prolactin has been implicated in promoting paternal care behaviors but little evidence of causality has been found to date except for birds and fish. This study was...
Prolactin has been implicated in promoting paternal care behaviors but little evidence of causality has been found to date except for birds and fish. This study was designed to examine the possible causal relationships between prolactin and male parenting behaviors, reproductive hormones, and physical changes in cooperatively breeding common marmosets, Callithrix jacchus. Fifteen parentally experienced fathers were studied over three consecutive infant care periods during two weeks prior and three weeks following their mates' parturition under three-treatment conditions: normal control pregnancy, decreased prolactin and elevated prolactin. The treatments significantly altered the serum prolactin levels in the fathers. Using three methods of determining a father's level of parental care: infant carrying, family effort and responsiveness to infant stimulus tests, we found that only the male response to infant stimuli was altered by the hormone treatments. Lowering prolactin significantly reduced male responsiveness to infant stimuli but elevating prolactin showed the same effect. Hormonal sampling indicated that testosterone levels showed an inverse relationship to prolactin levels during a normal peripartum period and prolactin treatment reduced this relationship. Prepartum estradiol levels were significantly elevated during the lowered prolactin treatment and estradiol was significantly lowered postpartum with the elevated prolactin treatment. Father's weight decreased significantly by the third week of infant care during the normal treatment. Males in the elevated prolactin treatment lost little or no weight from prepartum while in the lowered prolactin treatment showed the most weight loss. The present findings did not distinguish a direct causal relationship of prolactin on behavior in experienced fathers but did find an interaction with other hormones and weight gain.
Topics: Analysis of Variance; Animals; Behavior, Animal; Body Weight; Callithrix; Estradiol; Fathers; Male; Paternal Behavior; Prolactin; Random Allocation; Testosterone; Time Factors; Weight Loss
PubMed: 19664636
DOI: 10.1016/j.yhbeh.2009.07.012 -
Tijdschrift Voor Ziekenverpleging Oct 1975
Topics: Female; Humans; Prolactin
PubMed: 1043496
DOI: No ID Found -
Horumon To Rinsho. Clinical... 1975
Topics: Animals; Female; Humans; Pregnancy; Prolactin
PubMed: 1242046
DOI: No ID Found -
Journal of Mammary Gland Biology and... Jan 1997An enzymatically cleaved form of rat prolactin (rPRL) was first described in 1980. This cleavage produces a molecule that consists of two chains of amino acids linked by... (Review)
Review
An enzymatically cleaved form of rat prolactin (rPRL) was first described in 1980. This cleavage produces a molecule that consists of two chains of amino acids linked by a disulfide bond between two Cys residues. Reduction of that bond produces two fragments of 6 and 16 Kd. A considerable amount of information has accrued in recent years about the cleaved molecule and its 16-Kd fragment. The enzyme that cleaves the molecule is present in target tissues of PRL in rodents (e.g., mammary gland and ventral prostate), and the activity of the enzyme changes with the functional state of the mammary gland. Rat mammary PRL-cleaving activity is specific for rodent PRL, and the enzyme is localized in the stroma of that gland. The enzyme that cleaves rPRL is probably cathepsin D, and the sites of cleavage on the molecule have been identified. The cleaved form of rPRL has a high degree of activity in various assays, but it has reduced activity in radioimmunoassays. The 16-Kd fragment retains a significant degree of bioactivity in in vitro mitogenic assays, and specific binding sites for the fragment have been identified. Novel bioactivities for the cleaved form of rPRL and its 16-Kd fragment have been reported, and these molecules may account for the fact that bioassay estimates of PRL in rat serum are generally higher than are RIA measurements. Although the 16-Kd fragment has significant bioactivity, it contains only six of the fourteen residues that are thought to participate in the coupling of the intact hormone to its receptor. Cleaved rPRL is present in rat serum (but not in milk), but whether the 16-Kd fragment is formed in vivo has not yet been determined.
Topics: Animals; Binding Sites; Humans; Peptide Fragments; Prolactin; Radioimmunoassay; Rats; Receptors, Prolactin
PubMed: 10887522
DOI: 10.1023/a:1026329731268