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Ladyman SR, Brooks VL. Central actions of insulin during pregnancy and lactation. J Neuroendocrinol 2021; 33:e12946. [PMID: 33710714 PMCID: PMC9198112 DOI: 10.1111/jne.12946] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 01/24/2021] [Accepted: 01/27/2021] [Indexed: 12/17/2022]
Abstract
Pregnancy and lactation are highly metabolically demanding states. Maternal glucose is a key fuel source for the growth and development of the fetus, as well as for the production of milk during lactation. Hence, the maternal body undergoes major adaptations in the systems regulating glucose homeostasis to cope with the increased demand for glucose. As part of these changes, insulin levels are elevated during pregnancy and lower in lactation. The increased insulin secretion during pregnancy plays a vital role in the periphery; however, the potential effects of increased insulin action in the brain have not been widely investigated. In this review, we consider the impact of pregnancy on brain access and brain levels of insulin. Moreover, we explore the hypothesis that pregnancy is associated with site-specific central insulin resistance that is adaptive, allowing for the increases in peripheral insulin secretion without the consequences of increased central and peripheral insulin functions, such as to stimulate glucose uptake into maternal tissues or to inhibit food intake. Conversely, the loss of central insulin actions may impair other functions, such as insulin control of the autonomic nervous system. The potential role of low insulin in facilitating adaptive responses to lactation, such as hyperphagia and suppression of reproductive function, are also discussed. We end the review with a list of key research questions requiring resolution.
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Affiliation(s)
- Sharon R Ladyman
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
| | - Virginia L Brooks
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, USA
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Yu H, Thompson Z, Kiran S, Jones GL, Mundada L, Rubinstein M, Low MJ. Expression of a hypomorphic Pomc allele alters leptin dynamics during late pregnancy. J Endocrinol 2020; 245:115-127. [PMID: 32027603 DOI: 10.1530/joe-19-0576] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 02/06/2020] [Indexed: 12/11/2022]
Abstract
Proopiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus (ARC) are essential for normal energy homeostasis. Maximal ARC Pomc transcription is dependent on neuronal Pomc enhancer 1 (nPE1), located 12 kb upstream from the promoter. Selective deletion of nPE1 in mice decreases ARC Pomc expression by 70%, sufficient to induce mild obesity. Because nPE1 is located exclusively in the genomes of placental mammals, we questioned whether its hypomorphic mutation would also alter placental Pomc expression and the metabolic adaptations associated with pregnancy and lactation. We assessed placental development, pup growth, circulating leptin and expression of Pomc, Agrp and alternatively spliced leptin receptor (LepR) isoforms in the ARC and placenta of Pomc∆1/∆1 and Pomc+/+ dams. Despite indistinguishable body weights, lean mass, food intake, placental histology and Pomc expression and overall pregnancy outcomes between the genotypes, Pomc ∆1/∆1 females had increased pre-pregnancy fat mass that paradoxically decreased to control levels by parturition. However, Pomc∆1/∆1 dams had exaggerated increases in circulating leptin, up to twice of that of the typically elevated levels in Pomc+/+ mice at the end of pregnancy, despite their equivalent fat mass. Pomc∆1/∆1dams also had increased placental expression of soluble leptin receptor (LepRe), although the protein levels of LEPRE in circulation were the same as Pomc+/+ controls. Together, these data suggest that the hypomorphic Pomc∆1/∆1 allele is responsible for the perinatal super hyperleptinemia of Pomc∆1/∆1 dams, possibly due to upregulated leptin secretion from individual adipocytes.
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Affiliation(s)
- Hui Yu
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Zoe Thompson
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Sylee Kiran
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,School of Literature, Science, and Arts, University of Michigan, Ann Arbor, Michigan, USA
| | - Graham L Jones
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Lakshmi Mundada
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Marcelo Rubinstein
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Instituto de Investigaciones en Ingeniería Genética y Biología Molecular Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos, Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Khant Aung Z, Grattan DR, Ladyman SR. Pregnancy-induced adaptation of central sensitivity to leptin and insulin. Mol Cell Endocrinol 2020; 516:110933. [PMID: 32707081 DOI: 10.1016/j.mce.2020.110933] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 06/22/2020] [Accepted: 06/29/2020] [Indexed: 02/07/2023]
Abstract
Pregnancy is a time of increased food intake and fat deposition in the mother, and adaptations of glucose homeostasis to meet the energy demands of the growing fetus. As part of these adaptations, leptin and insulin concentrations increase in the maternal circulation during pregnancy. Central effects of leptin and insulin, however, are counterproductive to pregnancy, as increased action of these hormones in the brain lead to suppression of food intake. To prevent this, it is well documented that pregnancy induces a state of leptin- and insulin-insensitivity in the brain, particularly the hypothalamus, in a range of species. While the mechanisms underlying leptin- or insulin-insensitivity during pregnancy vary between species, there is evidence of reduced transport into the brain, impaired activation of intracellular signalling pathways, including reduced leptin receptor expression, and attenuated activation of downstream neuronal pathways, especially for leptin insensitivity. Pregnancy-induced changes in prolactin, growth hormone and leptin are discussed in terms of their role in mediating this reduced response to leptin and insulin.
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Affiliation(s)
- Z Khant Aung
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, 9016, New Zealand
| | - D R Grattan
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, 9016, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, 1010, New Zealand
| | - S R Ladyman
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, 9016, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, 1010, New Zealand.
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4
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Grattan DR, Ladyman SR. Neurophysiological and cognitive changes in pregnancy. HANDBOOK OF CLINICAL NEUROLOGY 2020; 171:25-55. [PMID: 32736755 DOI: 10.1016/b978-0-444-64239-4.00002-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The hormonal fluctuations in pregnancy drive a wide range of adaptive changes in the maternal brain. These range from specific neurophysiological changes in the patterns of activity of individual neuronal populations, through to complete modification of circuit characteristics leading to fundamental changes in behavior. From a neurologic perspective, the key hormone changes are those of the sex steroids, estradiol and progesterone, secreted first from the ovary and then from the placenta, the adrenal glucocorticoid cortisol, as well as the anterior pituitary peptide hormone prolactin and its pregnancy-specific homolog placental lactogen. All of these hormones are markedly elevated during pregnancy and cross the blood-brain barrier to exert actions on neuronal populations through receptors expressed in specific regions. Many of the hormone-induced changes are in autonomic or homeostatic systems. For example, patterns of oxytocin and prolactin secretion are dramatically altered to support novel physiological functions. Appetite is increased and feedback responses to metabolic hormones such as leptin and insulin are suppressed to promote a positive energy balance. Fundamental physiological systems such as glucose homeostasis and thermoregulation are modified to optimize conditions for fetal development. In addition to these largely autonomic changes, there are also changes in mood, behavior, and higher processes such as cognition. This chapter summarizes the hormonal changes associated with pregnancy and reviews how these changes impact on brain function, drawing on examples from animal research, as well as available information about human pregnancy.
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Affiliation(s)
- David R Grattan
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
| | - Sharon R Ladyman
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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Liu K, Cao H, Dong X, Liu H, Wen Y, Mao H, Lu L, Yin Z. Polymorphisms of pro-opiomelanocortin gene and the association with reproduction traits in chickens. Anim Reprod Sci 2019; 210:106196. [PMID: 31635770 DOI: 10.1016/j.anireprosci.2019.106196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 09/17/2019] [Accepted: 09/24/2019] [Indexed: 12/16/2022]
Abstract
Pro-opiomelanocortin (POMC) is a member of prohormone family and has important functions in stress response, skin pigmentation, thermoregulation and reproduction. In this study, the single nucleotide polymorphisms (SNPs) of POMC gene exons were detected by direct sequencing in 317 Zhenning yellow chickens. The sequencing results indicated there were seven mutation sites (g.1140C > T, g.1185 T > C, g.2085 T > C, g.3566A > C, g.3572 G > A, g.3594 G > A and g.3628 G > A) and all of these were synonymous. Furthermore, seven haplotypes were formed and sixteen diplotypes were obtained. The associations between the POMC gene polymorphisms or diplotypes and reproduction traits were also analyzed. The association analysis results indicated that the SNP of g.1140C > T was associated with egg production at 300 d of age (E300), fertilization rate (FR), hatching rate of hatching eggs (HEHR) and hatching rate of fertilized eggs (FEHR; P < 0.05). The SNP of g.3566A>C was associated with FR (P < 0.05), SNP of g.3594G>A was associated with egg weight at 300d of age (EW300; P < 0.05), and SNP of g.3628G>A was associated with HEHR and FEHR (P < 0.01), respectively. Furthermore, chickens with H2H3 diplotype had greater EW300 and FR than those with H1H7 and H3H4 diplotypes (P < 0.05). These results indicate the expression of the POMC gene had significant genotype effects on the reproduction traits of Zhenning yellow chickens, and that the H2H3 diplotype could be used as a potential genetic marker to improve the reproduction traits in chicken breeding.
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Affiliation(s)
- Ke Liu
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Haiyue Cao
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Xinyang Dong
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Honghua Liu
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Yaya Wen
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Haiguang Mao
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
| | - Lei Lu
- Ningbo Zhenning Animal Husbandry Co. Ltd, Ningbo 315000, China
| | - Zhaozheng Yin
- College of Animal Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China.
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6
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Histological and Metabolic State of Dams Suckling Small Litter or MSG-Treated Pups. ScientificWorldJournal 2016; 2016:1678541. [PMID: 28004032 PMCID: PMC5149680 DOI: 10.1155/2016/1678541] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 06/13/2016] [Accepted: 08/16/2016] [Indexed: 11/25/2022] Open
Abstract
Lactation is an important function that is dependent on changes in the maternal homeostasis and sustained by histological maternal adjustments. We evaluated how offspring manipulations during the lactational phase can modulate maternal morphologic aspects in the mammary gland, adipose tissue, and pancreatic islets of lactating dams. Two different models of litter-manipulation-during-lactation were used: litter sizes, small litters (SL) or normal litters (NL) and subcutaneous injections in the puppies of monosodium glutamate (MSG), or saline (CON). SL Dams and MSG Dams presented an increase in WAT content and higher plasma levels of glucose, triglycerides, and insulin, in relation to NL Dams and CON Dams, respectively. The MG of SL Dams and MSG Dams presented a high adipocyte content and reduced alveoli development and the milk of the SL Dams presented a higher calorie and triglyceride content, compared to that of the NL Dams. SL Dams presented a reduction in islet size and greater lipid droplet accumulation in BAT, in relation to NL Dams. SL Dams and MSG Dams present similar responses to offspring manipulation during lactation, resulting in changes in metabolic parameters. These alterations were associated with higher fat accumulation in BAT and changes in milk composition only in SL Dams.
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Abstract
Successfully rearing young places multiple demands on the mammalian female. These are met by a wide array of alterations in maternal physiology and behavior that are coordinated with the needs of the developing young, and include adaptations in neuroendocrine systems not directly involved in maternal behavior or lactation. In this article, attenuations in the behavioral and neuroendocrine responses to stressors, the alterations in metabolic pathways facilitating both increased food intake and conservation of energy, and the changes in fertility that occur postpartum are described. The mechanisms underlying these processes as well as the factors that contribute to them and the relative contributions of these stimuli at different times postpartum are also reviewed. The induction and maintenance of the adaptations observed in the postpartum maternal brain are dependent on mother-young interaction and, in most cases, on suckling stimulation and its consequences for the hormonal profile of the mother. The peptide hormone prolactin acting on receptors within the brain makes a major contribution to changes in metabolic pathways, suppression of fertility and the attenuation of the neuroendocrine response to stress during lactation. Oxytocin is also released, both into the circulation and in some hypothalamic nuclei, in response to suckling stimulation and this hormone has been implicated in the decrease in anxiety behavior seen in the early postpartum period. The relative importance of these hormones changes across lactation and it is becoming increasingly clear that many of the adaptations to motherhood reviewed here reflect the outcome of multiple influences. © 2016 American Physiological Society. Compr Physiol 6:1493-1518, 2016.
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Affiliation(s)
- Barbara Woodside
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montreal, Quebec, Canada
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Saul MC, Zhao C, Driessen TM, Eisinger BE, Gammie SC. MicroRNA expression is altered in lateral septum across reproductive stages. Neuroscience 2015; 312:130-40. [PMID: 26592715 DOI: 10.1016/j.neuroscience.2015.11.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/06/2015] [Accepted: 11/10/2015] [Indexed: 02/08/2023]
Abstract
MicroRNAs (miRNAs) inhibit RNA targets and may contribute to postpartum central nervous system (CNS) gene expression changes, although this has never been tested. In the present study, we directly evaluated miRNA levels using RNA sequencing during reproduction in female mice in the lateral septum (LS). We found the reliable and robust changes of miRNAs away from the virgin stage at the three other stages, namely pregnant, day 1 postpartum, and day 8 postpartum. For a given miRNA that was significantly different from the virgin condition in more than one group, the direction of change was always the same. Overall, we identified 32 upregulated miRNAs and 25 downregulated miRNAs that were consistently different from the virgin state. 'Arm switching' occurs for miR-433-3 and miR-7b. Unexpectedly, a third of upregulated miRNAs (relative to virgin) were highly localized within the 12qF1 region of chromosome 12 that includes the Dlk1-Dio3 gene cluster implicated in stem cell and neuronal differentiation. Over 1500 genes were targeted by multiple upregulated miRNAs with about 100 genes targeted by five or more miRNAs. Over 1000 genes were targeted by multiple downregulated miRNAs with about 50 genes targeted by five or more miRNAs. Half of the target genes were regulated by up and downregulated miRNAs, indicating homeostatic regulation. Transcriptional regulation was the most enriched pathway for genes linked to up or down regulated miRNAs. Other enriched pathways included protein kinase activity (e.g., MAP kinase), CNS development, axon guidance, neurotrophin signaling, neuron development/differentiation, and neurogenesis. Previously published postpartum LS gene expression changes were enrichment for LS miRNA targets, as expected. Surprisingly, postpartum gene expression changes from other regions were also enriched against LS miRNA targets, suggesting a core group of miRNAs may act across the CNS during reproduction. Together, we directly examine miRNAs and find significant alterations in the postpartum brain.
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Affiliation(s)
- M C Saul
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA
| | - C Zhao
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA
| | - T M Driessen
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA
| | - B E Eisinger
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA
| | - S C Gammie
- Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA; Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI, USA.
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Shi Z, Cassaglia PA, Gotthardt LC, Brooks VL. Hypothalamic Paraventricular and Arcuate Nuclei Contribute to Elevated Sympathetic Nerve Activity in Pregnant Rats: Roles of Neuropeptide Y and α-Melanocyte-Stimulating Hormone. Hypertension 2015; 66:1191-8. [PMID: 26483343 DOI: 10.1161/hypertensionaha.115.06045] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 09/17/2015] [Indexed: 11/16/2022]
Abstract
Pregnancy increases sympathetic nerve activity (SNA), but the mechanisms are unknown. Here, we investigated the contributions of the hypothalamic paraventricular and arcuate nuclei in α-chloralose-anesthetized pregnant and nonpregnant rats. Baseline arterial pressure (AP) was lower, and heart rate (HR), lumbar sympathetic activity, and splanchnic SNA were higher in pregnant rats compared with nonpregnant rats. Inhibition of the paraventricular nucleus via bilateral muscimol nanoinjections decreased AP and HR more in pregnant rats than in nonpregnant rats and decreased lumbar SNA only in pregnant rats. Similarly, after arcuate muscimol nanoninjections, the decreases in AP, HR, and lumbar, renal, and splanchnic sympathetic nerve activities were greater in pregnant rats than in nonpregnant rats. Major arcuate neuronal groups that project to the paraventricular nucleus express inhibitory neuropeptide Y (NPY) and excitatory α-melanocyte-stimulating hormone. Inhibition of paraventricular melanocortin 3/4 receptors with SHU9119 also decreased AP, HR, and lumbar SNA in pregnant rats but not in nonpregnant rats. Conversely, paraventricular nucleus NPY expression was reduced in pregnant animals, and although blockade of paraventricular NPY Y1 receptors increased AP, HR, and lumbar sympathetic activity in nonpregnant rats, it had no effects in pregnant rats. Yet, the sympathoinhibitory, depressor, and bradycardic effects of paraventricular NPY nanoinjections were similar between groups. In conclusion, the paraventricular and arcuate nuclei contribute to increased basal SNA during pregnancy, likely due in part to decreased tonic NPY inhibition and increased tonic α-melanocyte-stimulating hormone excitation of presympathetic neurons in the paraventricular nucleus.
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Affiliation(s)
- Zhigang Shi
- From the Department of Physiology and Pharmacology, Oregon Health & Science University, Portland
| | - Priscila A Cassaglia
- From the Department of Physiology and Pharmacology, Oregon Health & Science University, Portland
| | - Laura C Gotthardt
- From the Department of Physiology and Pharmacology, Oregon Health & Science University, Portland
| | - Virginia L Brooks
- From the Department of Physiology and Pharmacology, Oregon Health & Science University, Portland.
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Eisinger BE, Driessen TM, Zhao C, Gammie SC. Medial prefrontal cortex: genes linked to bipolar disorder and schizophrenia have altered expression in the highly social maternal phenotype. Front Behav Neurosci 2014; 8:110. [PMID: 24765068 PMCID: PMC3980118 DOI: 10.3389/fnbeh.2014.00110] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/15/2014] [Indexed: 11/14/2022] Open
Abstract
The transition to motherhood involves CNS changes that modify sociability and affective state. However, these changes also put females at risk for post-partum depression and psychosis, which impairs parenting abilities and adversely affects children. Thus, changes in expression and interactions in a core subset of genes may be critical for emergence of a healthy maternal phenotype, but inappropriate changes of the same genes could put women at risk for post-partum disorders. This study evaluated microarray gene expression changes in medial prefrontal cortex (mPFC), a region implicated in both maternal behavior and psychiatric disorders. Post-partum mice were compared to virgin controls housed with females and isolated for identical durations. Using the Modular Single-set Enrichment Test (MSET), we found that the genetic landscape of maternal mPFC bears statistical similarity to gene databases associated with schizophrenia (5 of 5 sets) and bipolar disorder (BPD, 3 of 3 sets). In contrast to previous studies of maternal lateral septum (LS) and medial preoptic area (MPOA), enrichment of autism and depression-linked genes was not significant (2 of 9 sets, 0 of 4 sets). Among genes linked to multiple disorders were fatty acid binding protein 7 (Fabp7), glutamate metabotropic receptor 3 (Grm3), platelet derived growth factor, beta polypeptide (Pdgfrb), and nuclear receptor subfamily 1, group D, member 1 (Nr1d1). RT-qPCR confirmed these gene changes as well as FMS-like tyrosine kinase 1 (Flt1) and proenkephalin (Penk). Systems-level methods revealed involvement of developmental gene networks in establishing the maternal phenotype and indirectly suggested a role for numerous microRNAs and transcription factors in mediating expression changes. Together, this study suggests that a subset of genes involved in shaping the healthy maternal brain may also be dysregulated in mental health disorders and put females at risk for post-partum psychosis with aspects of schizophrenia and BPD.
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Affiliation(s)
- Brian E Eisinger
- Department of Zoology, University of Wisconsin-Madison Madison, WI, USA
| | - Terri M Driessen
- Department of Zoology, University of Wisconsin-Madison Madison, WI, USA
| | - Changjiu Zhao
- Department of Zoology, University of Wisconsin-Madison Madison, WI, USA
| | - Stephen C Gammie
- Department of Zoology, University of Wisconsin-Madison Madison, WI, USA ; Neuroscience Training Program, University of Wisconsin-Madison Madison, WI, USA
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Suzuki Y, Nakahara K, Maruyama K, Okame R, Ensho T, Inoue Y, Murakami N. Changes in mRNA expression of arcuate nucleus appetite-regulating peptides during lactation in rats. J Mol Endocrinol 2014; 52:97-109. [PMID: 24299740 PMCID: PMC3907180 DOI: 10.1530/jme-13-0015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The contribution of hypothalamic appetite-regulating peptides to further hyperphagia accompanying the course of lactation in rats was investigated by using PCR array and real-time PCR. Furthermore, changes in the mRNA expression for appetite-regulating peptides in the hypothalamic arcuate nucleus (ARC) were analyzed at all stages of pregnancy and lactation, and also after weaning. Food intake was significantly higher during pregnancy, lactation, and after weaning than during non-lactation periods. During lactation, ARC expression of mRNAs for agouti-related protein (AgRP) and peptide YY was increased, whereas that of mRNAs for proopiomelanocortin (POMC) and cholecystokinin (CCK) was decreased, in comparison with non-lactation periods. The increase in AgRP mRNA expression during lactation was especially marked. The plasma level of leptin was significantly decreased during the course of lactation, whereas that of acyl-ghrelin was unchanged. In addition, food intake was negatively correlated with the plasma leptin level during lactation. This study has clarified synchronous changes in the expression of many appetite-regulating peptides in ARC of rats during lactation. Our results suggest that hyperphagia during lactation in rats is caused by decreases in POMC and CCK expression and increases in AgRP expression in ARC, the latter being most notable. Together with the decrease in the blood leptin level, such changes in mRNA expression may explain the further hyperphagia accompanying the course of lactation.
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Affiliation(s)
- Yoshihiro Suzuki
- Department of Veterinary Physiology, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan
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12
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Woodside B, Budin R, Wellman MK, Abizaid A. Many mouths to feed: the control of food intake during lactation. Front Neuroendocrinol 2012; 33:301-14. [PMID: 23000403 DOI: 10.1016/j.yfrne.2012.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 09/04/2012] [Accepted: 09/05/2012] [Indexed: 01/07/2023]
Abstract
Providing nutrients to their developing young is perhaps the most energetically demanding task facing female mammals. In this paper we focus primarily on studies carried out in rats to describe the changes in the maternal brain that enable the dam to meet the energetic demands of her offspring. In rats, providing milk for their litter is associated with a dramatic increase in caloric intake, a reduction in energy expenditure and changes in the pattern of energy utilization as well as storage. These behavioral and physiological adaptations result, in part, from alterations in the central pathways controlling energy balance. Differences in circulating levels of metabolic hormones such as leptin, ghrelin and insulin as well as in responsiveness to these signals between lactating and nonlactating animals, contribute to the modifications in energy balance pathways seen postpartum. Suckling stimulation from the pups both directly, and through the hormonal state that it induces in the mother, plays a key role in facilitating these adaptations.
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Affiliation(s)
- Barbara Woodside
- Center for Studies in Behavioral Neurobiology/Groupe de recherches en neurobiologie comportementale, Concordia University, Montreal, Canada.
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Gene expression changes in the septum: possible implications for microRNAs in sculpting the maternal brain. PLoS One 2012; 7:e38602. [PMID: 22701680 PMCID: PMC3368935 DOI: 10.1371/journal.pone.0038602] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/12/2012] [Indexed: 01/08/2023] Open
Abstract
The transition from the non-maternal to the maternal state is characterized by a variety of CNS alterations that support the care of offspring. The septum (including lateral and medial portions) is a brain region previously linked to various emotional and motivational processes, including maternal care. In this study, we used microarrays (PLIER algorithm) to examine gene expression changes in the septum of postpartum mice and employed gene set enrichment analysis (GSEA) to identify possible regulators of altered gene expression. Genes of interest identified as differentially regulated with microarray analysis were validated with quantitative real-time PCR. We found that fatty acid binding protein 7 (Fabp7) and galanin (Gal) were downregulated, whereas insulin-like growth factor binding protein 3 (Igfbp3) was upregulated in postpartum mice compared to virgin females. These genes were previously found to be differentially regulated in other brain regions during lactation. We also identified altered expression of novel genes not previously linked to maternal behavior, but that could play a role in postpartum processes, including glutamate-ammonia ligase (Glul) and somatostatin receptor 1 (Sstr1) (both upregulated in postpartum). Genes implicated in metabolism, cell differentiation, or proliferation also exhibited altered expression. Unexpectedly, enrichment analysis revealed a high number of microRNAs, transcription factors, or conserved binding sites (177 with corrected P-value <0.05) that were significantly linked to maternal upregulated genes, while none were linked to downregulated genes. MicroRNAs have been linked to placenta and mammary gland development, but this is the first indication they may also play a key role in sculpting the maternal brain. Together, this study provides new insights into genes (along with possible mechanisms for their regulation) that are involved in septum-mediated adaptations during the postpartum period.
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Cui JG, Tang GB, Wang DH, Speakman JR. Effects of leptin infusion during peak lactation on food intake, body composition, litter growth, and maternal neuroendocrine status in female Brandt's voles (Lasiopodomys brandtii). Am J Physiol Regul Integr Comp Physiol 2010; 300:R447-59. [PMID: 21123757 DOI: 10.1152/ajpregu.00121.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
During lactation, female small mammals frequently reduce their fat reserves to very low levels. The function of this reduction is unclear, as calculations suggest that the contribution of the withdrawn energy from fat to the total energy balance of lactation is trivial. An alternative hypothesis is that reducing fat leads to a reduction in circulating adipokines, such as leptin, that play a role in stimulating the hyperphagia of lactation. We investigated the role of circulating leptin in lactation by repleting leptin levels using miniosmotic pumps during the last 7 days of lactation in Brandt's voles (Lasiopodomys brandtii), a model small wild mammal we have extensively studied in the context of lactation energy demands. Repletion of leptin resulted in a dose-dependent reduction of body mass and food intake in lactating voles. Comparisons to nonreproducing individuals suggests that the reduced leptin in lactation, due to reduced fat stores, may account for ∼16% of the lactational hyperphagia. Reduced leptin in lactation may, in part, cause lactational hyperphagia via stimulatory effects on hypothalamic orexigenic neuropeptides (neuropeptide Y and agouti-related peptide) and inhibition of the anorexigenic neuropeptide (proopiomelanocortin). These effects were reversed by the experimental repletion of leptin. There was no significant effect of leptin treatment on daily energy expenditure, milk production or pup growth, but leptin repletion did result in a reversal of the suppression of uncoupling protein-1 levels in brown adipose tissue, indicating an additional role for reducing body fat and leptin during peak lacation.
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Affiliation(s)
- Jian-Guo Cui
- Institute of Zoology, Chinese Academy of Sciences, Benchen Xilu, Chaoyang, Beijing 100101, China
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15
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López N, Sánchez J, Picó C, Palou A, Serra F. Dietary l-leucine supplementation of lactating rats results in a tendency to increase lean/fat ratio associated to lower orexigenic neuropeptide expression in hypothalamus. Peptides 2010; 31:1361-7. [PMID: 20347902 DOI: 10.1016/j.peptides.2010.03.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 03/22/2010] [Accepted: 03/22/2010] [Indexed: 11/28/2022]
Abstract
The aim of this study was to assess the effects of dietary leucine supplementation in lactating dams, particularly on energy homeostasis through signaling mechanisms in the central nervous system. Dams were fed ad libitum with standard diet during pregnancy (control dams) or supplemented with 2% leucine (leucine-supplemented dams) from delivery onwards. Food intake, body weight and composition were periodically recorded. Hypothalamus was collected at the end of lactation, and the expression of neuropeptide Y (NPY), agouti-related protein (AgRP) pro-opiomelanocortin (POMC), cocaine and amphetamine regulated transcript (CART), insulin receptor (InsR), ghrelin receptor (GSHR), melanocortin receptor (MCR4), leptin receptor (Ob-Rb) and suppressor of cytokine signaling 3 (SOCS3) were analyzed. Dietary leucine supplementation to lactating rats increased plasma leucine by 56%, modulated body composition and contributed to a tendency of higher ratio of lean/fat mass content of dams during lactation, without affecting food intake, thermogenesis capacity or body or tissue/organs weights. No differences in body weight of offspring from control and leucine-supplemented dams were found. The expression of orexigenic peptides (NPY and AgRP) decreased in leucine-dams, whereas the expression of anorexigenic peptides (POMC and CART), the hypothalamic receptors of insulin, ghrelin, melanocortin and leptin and SOCS3 did not change by leucine supplementation. In conclusion, increased leucine intake during lactation may contribute to a healthier profile of body composition in dams, without compromising the growth and development of the progeny by a mechanism associated with lower expression of orexigenic neuropeptides in hypothalamus.
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Affiliation(s)
- N López
- Molecular Biology, Nutrition and Biotechnology (Nutrigenomics), University of the Balearic Islands (UIB) and CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Palma de Mallorca, Spain
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16
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Tavakoli-Nezhad M, Arbogast LA. Mu and kappa opioid receptor expression in the mediobasal hypothalamus and effectiveness of selective antagonists on prolactin release during lactation. Neuroscience 2010; 166:359-67. [PMID: 20045447 PMCID: PMC2824054 DOI: 10.1016/j.neuroscience.2009.12.066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 12/27/2009] [Accepted: 12/28/2009] [Indexed: 12/31/2022]
Abstract
Endogenous opioid peptides are involved in prolactin release during lactation, in part by decreasing tuberoinfundibular dopaminergic (TIDA) neuronal activity. Both mu (mu) and kappa (kappa) opioid receptors have a role in the suckling-induced prolactin rise after 4-5 h up deprivation. The aim of this study was to investigate effects of mu opioid receptor antagonist, beta-funaltrexamine (beta-FNA), and kappa opioid receptor antagonist, nor-binaltorphimine (nor-BNI), on prolactin secretion and TIDA neuronal activity in lactating rats after 18 h pup deprivation. After 4 h separation from pups, the suckling-induced prolactin rise was abolished by 16 microg nor-BNI and 5 microg beta-FNA, coincident with increased dihydroxyphenylacetic acid (DOPAC):dopamine ratio in the stalk-median eminence (SME). However, after 18 h pups separation, these same doses of nor-BNI and beta-FNA did not alter the prolactin surge or DOPAC:dopamine ratios in the SME. Higher doses of nor-BNI (32 microg) and beta-FNA (10 microg) were required to inhibit suckling-induced prolactin secretion. beta-FNA (10 microg) increased the DOPAC:dopamine ratio in the SME, whereas nor-BNI (32 microg) treatment had no effect. The mu and kappa opioid receptor mRNA levels in the mediobasal hypothalamus were similar to suckled control rats after 4 h pup deprivation, but increased 1.4-fold after 18 h pup deprivation. These data support involvement of endogenous opioidergic systems in the suckling-induced prolactin rise after a prolonged (18 h) period of pup deprivation, as well as the shorter (4 h) pup deprivation period previously reported. Suppression of TIDA neuronal activity likely played a part in mu opioid receptor input to the suckling-induced prolactin rise after both 4 h and 18 h separation, whereas non-dopaminergic input was implicated with kappa opioid receptors after 18 h pup deprivation. Increased mu and kappa opioid receptors gene expression in the mediobasal hypothalamus may contribute to reduced effectiveness of opioid receptor antagonists to block suckling-induced prolactin release after 18 h pup deprivation.
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Affiliation(s)
- M Tavakoli-Nezhad
- Department of Physiology, Mail Code 6523, School of Medicine, Southern Illinois University, Carbondale, IL 62901, USA
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17
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Byrnes EM, Babb JA, Bridges RS. Differential expression of oestrogen receptor alpha following reproductive experience in young and middle-aged female rats. J Neuroendocrinol 2009; 21:550-7. [PMID: 19500225 PMCID: PMC3104393 DOI: 10.1111/j.1365-2826.2009.01874.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reproductive experience (i.e. pregnancy and lactation) alters a number of physiological and behavioural endpoints, many of which are related to reproductive function and are regulated by oestrogen. For example, reproductive experience significantly attenuates the oestradiol-induced prolactin surge on the afternoon of pro-oestrous and circulating oestradiol levels are reduced at this time. Although parity-related effects on oestrogen receptor (ER) alpha have been observed within the anterior pituitary, there are currently no data regarding possible parity-induced alterations in ERalpha in the brain. Thus, the present study aimed to examine the effect of parity on the expression of ERalpha in reproductively relevant brain regions. Moreover, because previous findings have demonstrated that the long-term effects of reproductive experience are often oestrous cycle-dependent, ERalpha was examined at two stages of the oestrous cycle (i.e. dioestrous and pro-oestrous). Finally, because the expression of ERalpha is significantly influenced by age, both young and middle-aged females were included in the present study. ERalpha status was determined using immunohistochemistry in select brain regions involved in the regulation of reproductive behaviour in age-matched, cycling primiparous (i.e. one pregnancy and lactation) and nulliparous females as well as in age-matched, noncycling (i.e. persistent oestrous) 12 month-old primiparous and nulliparous females. Significant shifts in ERalpha cell numbers were observed in the medial preoptic area and medial amygdala as a consequence of reproductive experience in an oestrous-dependent manner. These findings indicate that significant changes in ERalpha activity occur in the brain as a function of reproductive experience.
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Affiliation(s)
- E M Byrnes
- Department of Biomedical Sciences, Tufts University, Cummings School of Veterinary Medicine, North Grafton, MA 01536, USA.
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18
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Ladyman SR, Tups A, Augustine RA, Swahn-Azavedo A, Kokay IC, Grattan DR. Loss of hypothalamic response to leptin during pregnancy associated with development of melanocortin resistance. J Neuroendocrinol 2009; 21:449-56. [PMID: 19302191 DOI: 10.1111/j.1365-2826.2009.01862.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hypothalamic leptin resistance during pregnancy is an important adaptation that facilitates the state of positive energy balance required for fat deposition in preparation for lactation. Within the arcuate nucleus, pro-opiomelanocortin (POMC) neurones and neuropeptide Y (NPY)/agouti-related gene protein (AgRP) neurones are first-order leptin responsive neurones involved in the regulation of energy balance. The present study aimed to investigate whether the regulation of these neuropeptides is disrupted during pregnancy in association with the development of leptin resistance. As measured by quantitative in situ hybridisation, POMC and AgRP mRNA levels were not significantly different during pregnancy, whereas NPY mRNA levels increased such that, by day 21 of pregnancy, levels were significantly higher than in nonpregnant, animals. These data suggest that these neurones were not responding normally to the elevated leptin found during pregnancy. To further characterise the melanocortin system during pregnancy, double-label immunohistochemistry was used to quantify leptin-induced phosphorylation of signal transducer and activator of transcription 3 (pSTAT3) in POMC neurones, using α-melanocyte-stimulating hormone (MSH) as a marker. The percentage of α-MSH neurones containing leptin-induced pSTAT3 did not significantly differ from nonpregnant animals, indicating that there was no change in the number of POMC neurones that respond to leptin during pregnancy. Treatment with α-MSH significantly reduced food intake in nonpregnant rats, but not in pregnant rats, indicating resistance to the satiety actions of α-MSH during pregnancy. The data suggest that multiple mechanisms contribute to leptin resistance during pregnancy. As well as a loss of responses in first-order leptin-responsive neurones in the arcuate nucleus, there is also a downstream disruption in the melanocortin system.
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Affiliation(s)
- S R Ladyman
- Centre for Neuroendocrinology, Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand
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19
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Abstract
Hypothalamic neurons that express agouti-related protein (AgRP) and neuropeptide Y (NPY) are thought to be important for regulation of feeding, especially under conditions of negative energy balance. The expression of NPY and AgRP increases during lactation and may promote the hyperphagia that ensues. We explored the role of AgRP neurons in reproduction and lactation, using a mouse model in which AgRP-expressing neurons were selectively ablated by the action of diphtheria toxin. We show that ablation of AgRP neurons in neonatal mice does not interfere with pregnancy, parturition, or lactation, suggesting that early ablation allows compensatory mechanisms to become established. However, ablation of AgRP neurons after lactation commences results in rapid starvation, indicating that both basal feeding and lactation-induced hyperphagia become dependent on AgRP neurons in adulthood. We also show that constitutive inactivation of Npy and Agrp genes does not prevent pregnancy or lactation, nor does it protect lactating dams from diphtheria toxin-induced starvation.
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Affiliation(s)
- Colin T Phillips
- Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
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20
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Byrnes EM. Chronic morphine exposure during puberty induces long-lasting changes in opioid-related mRNA expression in the mediobasal hypothalamus. Brain Res 2007; 1190:186-92. [PMID: 18083149 DOI: 10.1016/j.brainres.2007.11.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 10/26/2007] [Accepted: 11/09/2007] [Indexed: 12/31/2022]
Abstract
Substance abuse in developing females may have significant long-term effects on reproductive competency. Chronic morphine exposure during puberty has been shown to reduce prolactin secretion in lactating rats. Opioid activity within the mediobasal hypothalamus (MBH) regulates suckling-induced prolactin secretion. Thus, the current study was conducted to determine whether chronic pubertal morphine exposure alters the expression of mu- and/or kappa-opioid receptor mRNA or pro-opioimelanocortin (POMC) mRNA within the MBH. Using an increasing dose regimen, female Sprague-Dawley rats were injected twice daily for a total of 20 days with morphine sulfate or saline beginning at 30 days of age. Several weeks later, quantitative RT-PCR was used to determine mRNA expression within the MBH in diestrus, never pregnant (nulliparous) controls, postpartum day 5 (PPD5), PPD10, PPD18, and diestrus, reproductively experienced (primiparous) females. Pubertal morphine exposed females had increased mu- and kappa-receptor mRNA expression as well as decreased POMC mRNA expression on diestrus. During lactation, mu- and kappa-receptor mRNA expression in the MBH decreased while POMC mRNA expression increased in similarly treated females. No changes in mRNA expression were observed during lactation in pubertal saline-treated females; however, increased mu- and kappa-receptor mRNA expression as well as decreased POMC mRNA expression was observed in primiparous, pubertal saline-treated females when compared to nulliparous controls. Thus, chronic morphine exposure during puberty results in long-term alterations in mu- and kappa-receptor as well as POMC mRNA expression in the MBH which are similar to the changes observed following reproductive experience. These changes do not correlate with the decreased prolactin secretion observed during early lactation; however, they do demonstrate the enduring nature of the effects of chronic opiate exposure during puberty on hypothalamic opioid systems in adulthood.
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Affiliation(s)
- Elizabeth M Byrnes
- Department of Biomedical Sciences, Tufts University, Cummings School of Veterinary Medicine, North Grafton, MA 01536, USA.
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21
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Abstract
The nutritional needs of developing young place a large energetic demand on lactating females. In this paper some of the mechanisms through which lactating rats meet these demands are described. Emphasis is placed on the mechanisms that drive increased food intake in suckled rats that are independent of milk delivery and negative energy balance. Evidence is presented to suggest that prolactin (PRL), released from the pituitary in response to suckling stimulation, acts centrally to stimulate food intake during lactation. Brain areas in which PRL may act to stimulate food intake as well as its interactions with other hormones and neuropeptides involved in energy balance are discussed.
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Affiliation(s)
- Barbara Woodside
- Center for Studies in Behavioral Neurobiology, Concordia University, Montreal, Quebec, Canada.
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22
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Douglas AJ, Johnstone LE, Leng G. Neuroendocrine mechanisms of change in food intake during pregnancy: a potential role for brain oxytocin. Physiol Behav 2007; 91:352-65. [PMID: 17512024 DOI: 10.1016/j.physbeh.2007.04.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During pregnancy body weight, and particularly adiposity, increase, due to hyperphagia rather than decreased energy metabolism. These physiological adaptations provide the growing fetus(es) with nutrition and prepare the mother for the metabolically-demanding lactation period following birth. Mechanisms underlying the hyperphagia are still poorly understood. Although the peripheral signals that drive appetite and satiety centers of the brain are increased in pregnancy, the brain may become insensitive to their effects. For example, leptin secretion increases but hypothalamic resistance to leptin actions develops. However, several adaptations in hypothalamic neuroendocrine systems may converge to increase ingestive behavior. Oxytocin is one of the anorectic hypothalamic neuropeptides. Oxytocin neurons, both centrally-projecting parvocellular oxytocin neurons and central dendritic release of oxytocin from magnocellular neurons, may play a key role in regulating energy intake. During feeding in non-pregnant rats, magnocellular oxytocin neurons, especially those in the supraoptic nucleus, become strongly activated indicating their imminent role in meal termination. However, in mid-pregnancy the excitability of these neurons is reduced, central dendritic oxytocin release is inhibited and patterns of oxytocin receptor binding in the brain alter. Our recent data suggest that lack of central oxytocin action may partly contribute to maternal hyperphagia. However, although opioid inhibition is a major factor in oxytocin neuron restraint during pregnancy and opioids enhance food intake, an increase in opioid orexigenic actions were not observed. While changes in several central input pathways to oxytocin neurons are likely to be involved, the high level of progesterone secretion during pregnancy is probably the ultimate trigger for the adaptations.
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Affiliation(s)
- Alison J Douglas
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK.
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23
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Abstract
Despite elevated plasma leptin, food intake is increased during pregnancy leading to fat deposition. We have demonstrated that intracerebroventricular (icv) leptin is unable to suppress food intake in pregnant rats, as it does in non-pregnant animals. Hence, central leptin resistance develops during pregnancy. These changes are physiologically appropriate, providing increased energy reserves to help meet the high metabolic demands of fetal development and lactation. To characterise this central leptin resistance, we have measured levels of leptin receptor (Ob-Rb) mRNA in the hypothalamus, and examined leptin-induced phosphorylation of STAT3 (pSTAT3) in specific regions of the hypothalamus. In addition, to investigate the mechanism underlying pregnancy-induced leptin resistance, we have investigated effects of hormone treatments on hypothalamic responses to leptin in a pseudopregnant rat model. We observed a significant reduction of Ob-Rb mRNA levels in the ventromedial hypothalamic nucleus (VMH) during pregnancy, with no changes detected in other hypothalamic nuclei. Levels of leptin-induced pSTAT3 were specifically suppressed in the VMH and arcuate nucleus of pregnant rats compared to non-pregnant rats. Pseudopregnant rats were hyperphagic but did not become leptin resistant, suggesting that fetal or placental factors are required for the induction of leptin resistance. These data implicate the VMH as a key hypothalamic site involved in hormone-induced leptin resistance during pregnancy, and suggest that placental hormone secretion may mediate the hormone-induced loss of response to leptin.
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Affiliation(s)
- David R Grattan
- Centre for Neuroendocrinology and Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand.
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24
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Nahon JL. The melanocortins and melanin-concentrating hormone in the central regulation of feeding behavior and energy homeostasis. C R Biol 2006; 329:623-38; discussion 653-5. [PMID: 16860280 DOI: 10.1016/j.crvi.2006.03.021] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Accepted: 03/08/2006] [Indexed: 11/16/2022]
Abstract
A number of different neuropeptides exert powerful concerted controls on feeding behavior and energy balance, most of them being produced in hypothalamic neuronal networks under stimulation by anabolic and catabolic peripheral hormones such as ghrelin and leptin, respectively. These peptide-expressing neurons interconnect extensively to integrate the multiple opposing signals that mediate changes in energy expenditure. In the present review I have summarized our current knowledge about two key peptidic systems involved in regulating appetite and energy homeostasis, the melanocortin system (alpha-MSH, agouti and Agouti-related peptides, MC receptors and mahogany protein) and the melanin-concentrating hormone system (proMCH-derived peptides and MCH receptors) that contribute to satiety and feeding-initiation, respectively, with concurrent effects on energy expenditure. I have focused particularly on recent data concerning transgenic mice and the ongoing development of MC/MCH receptor antagonists/agonists that may represent promising drugs to treat human eating disorders on both sides of the energy balance (anorexia, obesity).
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Affiliation(s)
- Jean-Louis Nahon
- Institut de pharmacologie moléculaire et cellulaire, UMR 6097, Centre national de la recherche scientifique (CNRS), 660, route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France.
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25
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Gammie SC, Hasen NS, Awad TA, Auger AP, Jessen HM, Panksepp JB, Bronikowski AM. Gene array profiling of large hypothalamic CNS regions in lactating and randomly cycling virgin mice. ACTA ACUST UNITED AC 2006; 139:201-11. [PMID: 15953654 PMCID: PMC1373786 DOI: 10.1016/j.molbrainres.2005.05.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2004] [Revised: 04/20/2005] [Accepted: 05/12/2005] [Indexed: 11/20/2022]
Abstract
A dramatic example of neuronal and physiological plasticity in adult mammals occurs during the transition from a non-maternal to a maternal, lactating state. In this study, we compared gene expression within a large continuous region of the CNS involved in maternal behaviors (hypothalamus, preoptic regions, and nucleus accumbens) between lactating (L) (postpartum Day 7) and randomly cycling virgin (V) outbred mice. Using high-density oligonucleotide arrays representing 11,904 genes, two statistical algorithms were used to identify significant differences in gene expression: robust multiarray (P < 0.001) (n = 92 genes) and significance analysis of microarrays using a 10% false discover rate (n = 114 genes). 27 common genes were identified as significant using both techniques. A subset of genes (n = 5) were selected and examined by real-time PCR. Our findings were consistent with previous published work. For example, neuropeptide Y (NPY) and proenkephalin were elevated in L mice, whereas POMC was decreased. Increased levels of NPY Y2 receptor and polo-like kinase and decreased levels of endothelin receptor type b in L mice are examples of novel gene expression changes not previously identified. Expression differences occurred in broad classes. Together, our findings provide possible new material on gene expression changes that may support maternal behaviors. The advantages and drawbacks of sampling large CNS regions using arrays are discussed.
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Affiliation(s)
- Stephen C Gammie
- Department of Zoology, University of Wisconsin, 1117 W. Johnson Street, Madison, WI 53706, USA.
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26
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Kokay IC, Grattan DR. Expression of mRNA for prolactin receptor (long form) in dopamine and pro-opiomelanocortin neurones in the arcuate nucleus of non-pregnant and lactating rats. J Neuroendocrinol 2005; 17:827-35. [PMID: 16280030 DOI: 10.1111/j.1365-2826.2005.01374.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Under most conditions, prolactin secretion from the pituitary gland is subject to negative-feedback regulation. Prolactin stimulates dopamine release from tuberoinfundibular (TIDA) neurones in the arcuate nucleus of the hypothalamus, which in turn suppresses the production of prolactin. However, during late pregnancy and continuing into lactation, this feedback mechanism becomes less responsive to prolactin and, as a result, a hyperprolactinaemic state develops. We investigated whether long-form prolactin receptor (PRL-R(L)) mRNA is present on TIDA neurones in nonpregnant and lactating rats. In addition, we examined whether PRL-R(L) mRNA is colocalized on hypothalamic pro-opiomelanocortin (POMC) neurones. Dual-label in situ hybridizations using an (35)S-labelled cRNA probe specific for long-form PRL-R, together with a digoxigenin-labelled RNA probe that encoded either tyrosine hydroxylase (TH) or POMC mRNA, were performed on brain sections. In both nonpregnant and lactating rats, the majority of TH mRNA-positive cells (> 90%) were found to express long-form PRL-R mRNA. In sections from nonpregnant rats, few non-TH positive cells expressed PRL-R(L) mRNA. By contrast, during lactation, the proportion of PRL-R(L) mRNA-positive cells that were not TH mRNA-positive increased to approximately 70%. Only a small number of neurones in this subpopulation of PRL-R(L) mRNA-positive neurones were found to be positive for POMC mRNA. These data show that the loss of responsiveness to prolactin occurring during lactation is not due to down regulation of long-form PRL-R gene expression on TIDA neurones. Moreover, the persistent expression of PRL-R(L) in arcuate neuroendocrine circuits suggests that PRL-R-mediated signalling continues to be important in these neurones during lactation.
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Affiliation(s)
- I C Kokay
- Centre for Neuroendocrinology and Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand.
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27
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Douglas AJ. Central noradrenergic mechanisms underlying acute stress responses of the Hypothalamo-pituitary-adrenal axis: adaptations through pregnancy and lactation. Stress 2005; 8:5-18. [PMID: 16019594 DOI: 10.1080/10253890500044380] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Hypothalamo-pituitary-adrenal axis responses to stress are attenuated perinatally, and may contribute towards conservation of energy stores and/or prevention of overexposure to glucocorticoid and its adverse effects in the developing fetus/neonate. Previous work has shown that reduced central drive to the hypothalamo-pituitary-adrenal axis is responsible, since parvocellular paraventricular nucleus neurone responses are reduced. One of the main input pathways to the paraventricular nucleus that is activated by the majority of stressors is the brainstem noradrenergic system. This review outlines key noradrenergic mechanisms that mediate hypothalamo-pituitary-adrenal axis responses to acute stress, and addresses aspects of their adaptation in pregnancy and lactation that can explain the stress hyporesponsiveness at that time. In summary, reduced noradrenaline release and adrenergic receptor expression in the paraventricular nucleus may lead to reduced sensitivity of the hypothalamo-pituitary-adrenal axis to adrenergic antagonists and agonists and its responses to stress. While there are subtle differences in these changes between pregnancy and lactation, it would appear that reduced effectiveness of the noradrenergic input can at least partly account for the reduced hypothalamo-pituitary-adrenal axis responses both pre- and post-natally.
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Affiliation(s)
- Alison J Douglas
- Laboratory of Neuroendocrinology, Centre for Integrative Physiology, SBCLS, College of Medicine and Veterinary Medicine, University of Edinburgh, Hugh Robson Building, George Square, UK.
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28
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Douglas AJ, Meddle SL, Toschi N, Bosch OJ, Neumann ID. Reduced activity of the noradrenergic system in the paraventricular nucleus at the end of pregnancy: implications for stress hyporesponsiveness. J Neuroendocrinol 2005; 17:40-8. [PMID: 15720474 DOI: 10.1111/j.1365-2826.2005.01272.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We investigated whether changes in noradrenaline neurotransmission in the hypothalamus could explain the hyporesponsiveness of the hypothalamic-pituitary-adrenal (HPA) axis in late pregnancy. Noradrenaline release within the hypothalamic paraventricular nucleus in response to swim stress, as estimated by microdialysis and high-performance liquid chromatography, was lower in 20-day pregnant rats compared to virgin rats. Driving a central noradrenergic pathway using intravenous cholecystokinin increased adrenocorticotropic hormone (ACTH) secretion in virgin rats, but the response was significantly less in 16-day and 20-day pregnant rats. Thus, the activity of noradrenergic inputs to the paraventricular nucleus and the HPA axis is attenuated in late pregnancy. The sensitivity of the HPA axis to noradrenaline in pregnancy was investigated by intracerebroventricular administration of an alpha1-receptor antagonist, benoxathian, before and during exposure to swim stress. In virgin rats, benoxathian increased basal and stress-induced ACTH secretion, but in late pregnant rats the benoxathian effects were attenuated, indicating reduced sensitivity of the HPA axis to noradrenaline neurotransmission and/or the inability of the system to become disinhibited at this time. alpha1A-adrenoreceptor mRNA expression in the parvocellular and magnocellular paraventricular nucleus, measured by in situ hybridisation, was decreased in late pregnant compared to virgin rats. Additionally, blocking endogenous opioid inhibition with naloxone pretreatment restored the ACTH secretory response to cholecystokinin in pregnant rats. Thus, in late pregnancy, there is reduced noradrenergic input to the paraventricular nucleus and reduced alpha1A-receptor expression in the paraventricular nucleus, both of which may contribute to the reduced responsiveness of the HPA axis in pregnancy.
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Affiliation(s)
- A J Douglas
- Laboratory of Neuroendocrinology, Centre for Integrative Physiology, School of Biomedical and Clinical Laboratory Sciences, University of Edinburgh, Edinburgh, UK.
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29
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Abstract
Energy balance is maintained via a homeostatic system involving both the brain and the periphery. A key component of this system is the hypothalamus. Over the past two decades, major advances have been made in identifying an increasing number of peptides within the hypothalamus that contribute to the process of energy homeostasis. Under stable conditions, equilibrium exists between anabolic peptides that stimulate feeding behavior, as well as decrease energy expenditure and lipid utilization in favor of fat storage, and catabolic peptides that attenuate food intake, while stimulating sympathetic nervous system (SNS) activity and restricting fat deposition by increasing lipid metabolism. The equilibrium between these neuropeptides is dynamic in nature. It shifts across the day-night cycle and from day to day and also in response to dietary challenges as well as peripheral energy stores. These shifts occur in close relation to circulating levels of the hormones, leptin, insulin, ghrelin and corticosterone, and also the nutrients, glucose and lipids. These circulating factors together with neural processes are primary signals relaying information regarding the availability of fuels needed for current cellular demand, in addition to the level of stored fuels needed for long-term use. Together, these signals have profound impact on the expression and production of neuropeptides that, in turn, initiate the appropriate anabolic or catabolic responses for restoring equilibrium. In this review, we summarize the evidence obtained on nine peptides in the hypothalamus that have emerged as key players in this process. Data from behavioral, physiological, pharmacological and genetic studies are described and consolidated in an attempt to formulate a clear statement on the underlying function of each of these peptides and also on how they work together to create and maintain energy homeostasis.
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Affiliation(s)
- Sarah F Leibowitz
- Laboratory of Behavioral Neurobiology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
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30
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Rocha M, Bing C, Williams G, Puerta M. Pregnancy-induced hyperphagia is associated with increased gene expression of hypothalamic agouti-related peptide in rats. REGULATORY PEPTIDES 2003; 114:159-65. [PMID: 12832105 DOI: 10.1016/s0167-0115(03)00119-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pregnancy is characterized by an increase in food intake that, in turn, produce a positive energy balance in order to face the considerable metabolic demands associated with the challenge of reproduction. Since hypothalamus is a key brain region involved in many peripheral signals and neuronal pathways that control energy homeostasis and food intake, we investigated if during pregnancy the increase in food intake is mediated by stimulating orexigenic and/or inhibiting anorexigenic neural pathways. We examined hypothalamic gene expressions of Ob-Rb, NPY, AgRP, POMC, MC4-R, and preproorexins in pregnant Wistar rats at day 19 of gestation. Food intake and body weight were increased progressively during the pregnancy. Visceral fat mass depots and serum leptin levels were also increased when compared with virgin animals. No differences were found in mRNA expression of Ob-Rb, POMC, MC4-R, NPY or preproorexin between virgin and pregnant animals. However, pregnancy produced a selective increase in AgRP mRNA levels. These results indicate that the positive energy balance that occurred during pregnancy can hardly be explained by changes in Ob-Rb despite hyperleptinemia associated with pregnancy. The enhanced expression of AgRP suggests the involvement of this neuropeptide in mediating pregnancy-associated hyperphagia.
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Affiliation(s)
- Milagros Rocha
- Department of Animal Biology II (Physiology), Faculty of Biological Sciences, Complutense University, 28040 Madrid, Spain
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31
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Hill JW, Levine JE. Abnormal response of the neuropeptide Y-deficient mouse reproductive axis to food deprivation but not lactation. Endocrinology 2003; 144:1780-6. [PMID: 12697683 DOI: 10.1210/en.2002-221024] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Neuropeptide Y (NPY) plays a key role in both food intake and GnRH secretion. Food deprivation elevates hypothalamic NPY activity and suppresses LH and gonadal steroid secretion. Similarly, lactation up-regulates NPY expression as food consumption increases and estrous cycles cease. These observations suggest that NPY coordinates reproductive suppression in response to energy deficiency; if so, the reproductive axis of NPY knockout (KO) mice should be impervious to lactation and food deprivation. We monitored food consumption, body weight, and estrous cyclicity during lactation in NPY KO mice with large and small litters. NPY KO mice with either litter size resembled wild types (WTs) in weight regulation and food consumption. Large-litter mothers had longer anestrous periods and smaller pups at weaning, but NPY KOs and WTs did not differ in either respect. We also examined the LH response of NPY KO mice to 48 h without food. Basal levels of LH in ovariectomized NPY KO animals decreased in response to fasting, but LH levels in intact and estrogen-treated ovariectomized NPY KO animals did not. In contrast, WTs consistently showed fasting-induced suppression of LH. Our findings suggest that other systems can sustain the hyperphagia of lactation and NPY alone is not responsible for suppressing cyclicity during lactation. Nevertheless, the suppression of basal LH release that accompanies food deprivation in normal female mice appears to require the steroid-dependent actions of NPY.
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Affiliation(s)
- Jennifer W Hill
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA
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32
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Andrews ZB, Grattan DR. Opioid receptor subtypes involved in the regulation of prolactin secretion during pregnancy and lactation. J Neuroendocrinol 2003; 15:227-36. [PMID: 12588510 DOI: 10.1046/j.1365-2826.2003.00975.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Afferent endogenous opioid neuronal systems facilitate prolactin secretion in a number of physiological conditions including pregnancy and lactation, by decreasing tuberoinfundibular dopamine (TIDA) inhibitory tone. The aim of this study was to investigate the opioid receptor subtypes involved in regulating TIDA neuronal activity and therefore facilitating prolactin secretion during early pregnancy, late pregnancy and lactation in rats. Selective opioid receptor antagonists nor-binaltorphimine (kappa-receptor antagonist, 15 micro g/5 micro l), beta funaltrexamine (mu-receptor antagonist, 5 microg/5 microl) and naltrindole (delta-receptor antagonist, 5 microg/5 microl) or saline were administered intracerebroventricularly (i.c.v.) on day 8 of pregnancy during a nocturnal prolactin surge, on day 21 of pregnancy during the ante partum prolactin surge or on day 7 of lactation before the onset of a suckling stimulus. Serial blood samples were collected at regular time intervals, via chronic indwelling jugular cannulae, before and after drug administration and plasma prolactin was determined by radioimmunoassay. TIDA neuronal activity was measured using the 3,4-dihydroxyphenylacetic acid (DOPAC) : dopamine ratio in the median eminence 2 h 30 min after i.c.v. drug injection. In each experimental condition, plasma prolactin was significantly inhibited by both kappa- and mu-receptor antagonists, whereas the delta-receptor antagonist had no effect compared to saline-injected controls. Similarly, nor-binaltorphimine and beta funaltrexamine significantly increased the median eminence DOPAC : dopamine ratio during early and late pregnancy, and lactation whereas naltrindole had no effect compared to saline-injected controls. These data suggest that TIDA neuronal activity, and subsequent prolactin secretion, is regulated by endogenous opioid peptides acting at both kappa- and mu-opioid receptors during prolactin surges of early pregnancy, late pregnancy and lactation.
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MESH Headings
- Animals
- Female
- Injections, Intraventricular
- Lactation/metabolism
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Pituitary Gland/metabolism
- Pregnancy
- Pregnancy, Animal/metabolism
- Prolactin/blood
- Prolactin/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid/metabolism
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
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Affiliation(s)
- Z B Andrews
- Department of Anatomy and Structural Biology and Neuroscience Research Centre, School of Medical Sciences, University of Otago, Dunedin, New Zealand
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33
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Douglas AJ, Bicknell RJ, Leng G, Russell JA, Meddle SL. Beta-endorphin cells in the arcuate nucleus: projections to the supraoptic nucleus and changes in expression during pregnancy and parturition. J Neuroendocrinol 2002; 14:768-77. [PMID: 12372001 DOI: 10.1046/j.1365-2826.2002.00837.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Supraoptic nucleus oxytocin neurone activity and secretion are inhibited in late pregnancy and parturition by endogenous opioids. Here, we investigated alterations in the projections and gene expression of beta-endorphin/pro-opiomelanocortin neurones in the arcuate nucleus in the pregnant rat. All regions of the arcuate nucleus were found to contain cells immunoreactive for beta-endorphin fluorescent microbeads retrogradely transported from the supraoptic nucleus, and double-labelled neurones (beta-endorphin plus microbeads), showing that beta-endorphin neurones throughout the arcuate nucleus project to the supraoptic nucleus. There was an increase in the number of beta-endorphin-immunoreactive cells in the arcuate nucleus and an increase in the density of beta-endorphin fibres within the supraoptic nucleus and peri-supraoptic region in late pregnancy and parturition, suggesting enhanced expression of beta-endorphin and increased beta-endorphin innervation of the supraoptic nucleus. Pro-opiomelanocortin mRNA expression in the arcuate nucleus increased in late compared to early pregnancy: the number of positive neurones significantly increased in the caudal region. Fos expression (an indicator of neuronal activation) in the arcuate nucleus was colocalized in beta-endorphin neurones in both proestrus and parturient rats, but the number of positive cells did not increase during parturition, suggesting lack of activation of beta-endorphin neurones at birth. Thus, beta-endorphin cells in the arcuate nucleus project to the supraoptic nucleus and increased innervation during pregnancy may explain the enhanced endogenous opioid inhibition of oxytocin neurones.
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Affiliation(s)
- A J Douglas
- Division of Biomedical Sciences, University of Edinburgh, George Square, Edinburgh, UK.
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34
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Wigger A, Neumann ID. Endogenous opioid regulation of stress-induced oxytocin release within the hypothalamic paraventricular nucleus is reversed in late pregnancy: a microdialysis study. Neuroscience 2002; 112:121-9. [PMID: 12044477 DOI: 10.1016/s0306-4522(02)00068-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Oxytocin secretion into blood in response to swim stress is differentially regulated by endogenous opioids in virgin and pregnant rats. Here, the influence of endogenous opioids on oxytocin release within the hypothalamic paraventricular and supraoptic nuclei was investigated using microdialysis in virgin and pregnant (day 19-21) rats. Rats fitted with a U-shaped microdialysis probe 3 days before testing were injected with naloxone (5 mg/kg body weight, s.c.) or vehicle (sterile saline) and, 3 min later, were forced to swim (10 min at 19 degrees C). Within the paraventricular nucleus, basal and stimulated oxytocin release did not significantly differ between vehicle-treated virgin and pregnant rats. After naloxone, local oxytocin release in response to swimming was lowered in virgin rats (P<0.01), whereas it was further increased in pregnant rats (P<0.01). Within the supraoptic nucleus, basal oxytocin release was significantly lower in pregnant compared to virgin rats (P<0.01). Forced swimming induced a similar rise in intranuclear oxytocin release in both vehicle-treated virgin and pregnant rats, but peak levels were still higher in the virgin controls. In contrast to the paraventricular nucleus, naloxone did not alter swim-induced oxytocin release within the supraoptic nucleus either in virgin or pregnant rats. Vasopressin release in the paraventricular nucleus was also increased by forced swimming but there was no effect of pregnancy or naloxone on it. In summary, in pregnancy, basal and stress-induced oxytocin release within the paraventricular nucleus was not changed, whereas it was blunted within the supraoptic nucleus. Further, within the paraventricular nucleus the excitatory effect of endogenous opioids on local oxytocin release seen in virgins was switched into an inhibitory action in pregnancy. In contrast, endogenous opioids were evidently not involved in the regulation of swim-induced oxytocin release within the supraoptic nucleus either in virgin or pregnant rats. Thus, pregnancy-related neuroendocrine plasticity also includes site-specific functional alterations in opioid receptor-mediated actions in the hypothalamus.
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Affiliation(s)
- A Wigger
- Max Planck Institute of Psychiatry, Kraepelinstrasse 2, 80804 Munich, Germany
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35
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Russell JA, Douglas AJ, Ingram CD. Brain preparations for maternity--adaptive changes in behavioral and neuroendocrine systems during pregnancy and lactation. An overview. PROGRESS IN BRAIN RESEARCH 2001; 133:1-38. [PMID: 11589124 DOI: 10.1016/s0079-6123(01)33002-9] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pregnancy, parturition and lactation comprise a continuum of adaptive changes necessary for the development and maintenance of the offspring. The endocrine changes that are driven by the conceptus and are essential for the maintenance of pregnancy and are involved in the preparations for motherhood are outlined. These changes include large increases in the secretion of sex steroid hormones, and the secretion of peptide hormones that are unique to pregnancy. The ability of these pregnancy hormones to alter several aspects of brain function in pregnancy is considered, and the adaptive importance of some of these changes is discussed, for example in metabolic and body fluid adjustments, and the induction of maternal behavior. The importance of sex steroids in determining the timing of the various adaptive changes in preparing for parturition and maternal behavior is emphasized, and the concept that the actions of prolactin and oxytocin, quintessential mammalian motherhood neuropeptides, can serve to coordinate a spectrum of adaptive changes is discussed. The part played by oxytocin neurons and their regulatory mechanisms is reviewed to illustrate how neural systems involved in maternity are prepared in pregnancy via changes in phenotype, synaptic organization and in the relative importance of their different inputs, to function optimally when needed. For oxytocin neurons secreting from the posterior pituitary, important in parturition and essential in lactation, these changes include mechanisms to restrain their premature activation, and adaptations to support synchronized burst firing for pulsatile oxytocin secretion in response to stimulation via afferents from the birth canal, olfactory system or suckled nipples. Within the brain, expression of oxytocin receptors permits centrally released oxytocin to facilitate the expression of maternal behavior. Changes in other neuroendocrine systems are similarly extensive, leading to lactation, suppression of ovulation, reduced stress responses and increased appetite; these changes in lactation are driven by the suckling stimulus. The possible link between these adaptations and changes in cognition and mood in pregnancy and post partum are considered, as well as the dysfunctions that lead to common problems of depression and puerperal psychoses.
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Affiliation(s)
- J A Russell
- Laboratory of Neuroendocrinology, Section of Biomedical Sciences, Division of Biomedical and Clinical Laboratory Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
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36
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Douglas AJ, Russell JA. Endogenous opioid regulation of oxytocin and ACTH secretion during pregnancy and parturition. PROGRESS IN BRAIN RESEARCH 2001; 133:67-82. [PMID: 11589146 DOI: 10.1016/s0079-6123(01)33006-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Progress of parturition in the rat is optimal when there is increased oxytocin secretion, thus ensuring quick birth and otherwise risking adverse neonatal health. To ensure that the mechanisms for this are available, oxytocin neurons adapt in pregnancy and this includes development of a tonic inhibition by endogenous opioids. Endogenous opioid inhibition of oxytocin secretion increases in pregnancy, initially acting on the nerve terminals in the posterior pituitary and later on oxytocin cell bodies and their inputs. This inhibition enhances stores of oxytocin and enables restraint of oxytocin neuron responsiveness to selected excitatory inputs. The hypothalamic neurons which mediate stress also adapt in late pregnancy so that hypothalamo-pituitary-adrenal axis and oxytocin secretory responses to stressor exposure are attenuated. This is also partly due to endogenous opioid inhibition. Thus, in pregnancy oxytocin and hypothalamo-pituitary-adrenal axis secretion in response to stimulation is restrained, protecting the unborn fetus(es) from premature delivery and glucocorticoid exposure and preparing the oxytocin neurons for their important secretory role during parturition. In parturition itself, endogenous opioids continue to inhibit these neurons. Stress exposure during parturition delays births, probably due to endogenous opioid inhibition of pulsatile oxytocin secretion. On the other hand, basal ACTH and corticosterone secretion are reduced in parturition through inhibition by endogenous opioids. So, opioids continue to regulate the activity of oxytocin and hypothalamo-pituitary-adrenal mechanisms in labor; inhibition of oxytocin neurons at this time may control the spacing of pup births.
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Affiliation(s)
- A J Douglas
- Laboratory of Neuroendocrinology, Department of Biomedical Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK.
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37
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Speth RC, Barry WT, Smith MS, Grove KL. A comparison of brain angiotensin II receptors during lactation and diestrus of the estrous cycle in the rat. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:R904-9. [PMID: 10484510 DOI: 10.1152/ajpregu.1999.277.3.r904] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During lactation there are many dramatic alterations in the hypothalamic-pituitary (HP) axis, as well as an increased demand for food and water. The renin-angiotensin system (RAS) is one of the major mediators of the HP axis. This study examined the receptors for ANG II in the rat brain during lactation and diestrus. Compared with diestrus, lactating rats had significant decreases in ANG II receptor binding in several forebrain regions, most notably in the arcuate nucleus/median eminence, dorsomedial hypothalamic nucleus (DMH), and lateral hypothalamic area (LHA). In contrast, there was an increase in ANG II receptor binding in the preoptic area during lactation. These significant changes in ANG II binding in the brain during lactation support the hypothesis that changes in the RAS may contribute to the dramatic changes in the HP axis during lactation. In addition, the significant reduction in ANG II binding in the DMH and LHA may be indicative of a role in the regulation of food intake, a function only recently associated with the RAS.
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Affiliation(s)
- R C Speth
- Department of Veterinary Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, Washington 99164, USA
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38
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Mann PE, Foltz G, Rigero BA, Bridges RS. The development of POMC gene expression in the medial basal hypothalamus of prepubertal rats. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1999; 116:21-8. [PMID: 10446343 DOI: 10.1016/s0165-3806(99)00071-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alterations in brain opioid gene expression may underlie the dramatic change in the latency to display parental behavior in juvenile rats. Male and female juvenile rats (18-25 days of age) exhibit parental behavior either immediately or within 1-2 days after coming in contact with foster pups. By 30 days of age, however, their response latencies increase to adult levels of 5-10 days. Given the established involvement of the endogenous opioid system in adult maternal and juvenile parental behaviors, the objective of the present report was to determine possible changes in proopiomelanocortin (POMC) gene expression in the medial basal hypothalamus (MBH) during this early developmental window. We compared POMC gene expression in the MBH of male and female juvenile rats from 21 to 33 days of age by in situ hybridization histochemistry. A significant increase in the number of POMC cells in males and females was detected at 30 days of age in the central portion of the arcuate nucleus. This increase in POMC mRNA may contribute to the shift in parental behavior that occurs in male and female juvenile rats.
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Affiliation(s)
- P E Mann
- Department of Biomedical Sciences, Tufts University School of Veterinary Medicine, 200 Westboro Rd., N. Grafton, MA 01536, USA.
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39
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Arbogast LA, Voogt JL. Endogenous opioid peptides contribute to suckling-induced prolactin release by suppressing tyrosine hydroxylase activity and messenger ribonucleic acid levels in tuberoinfundibular dopaminergic neurons. Endocrinology 1998; 139:2857-62. [PMID: 9607794 DOI: 10.1210/endo.139.6.6052] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The endogenous opioid peptides have been implicated in the control of the suckling-induced PRL rise during lactation. This study examined the role of the endogenous opioid peptides in suppressing tuberoinfundibular dopaminergic neuronal activity during lactation. In the first experiment, lactating rats were constantly exposed to pups. Naloxone (NAL; 60 mg/kg x h; i.v.), an opioid receptor antagonist, or saline was infused for 12 h. Blood was collected before and at 2-h intervals during the infusion. NAL suppressed circulating PRL levels to less than 36% of control values at 4, 6, 8, and 12 h after the onset of the infusion. Tyrosine hydroxylase (TH) activity in the stalk-median eminence and TH messenger RNA signal levels in the arcuate nucleus were determined at the end of the NAL infusion. TH activity and TH messenger RNA signal levels were increased 2.5- and 2.7-fold, respectively, after the 12-h NAL infusion. Even though the time spent with their pups was similar between the two groups, the pups in the NAL-treated group failed to gain weight during the 12-h NAL infusion period, whereas the control litters (8 pups) gained 5 g. In a second experiment, pups were removed from the dams before the 12-h NAL infusion and were returned after 11 h. Blood was collected before the infusion, at 3-h intervals during the pup separation period, and at 15-min intervals after reunion with the pups. Plasma PRL in control and NAL-treated rats was low (1-15 ng/ml) and similar during the separation period. The suckling-induced PRL surge in NAL-treated rats was markedly attenuated to 9-25% of control levels (350-650 ng/ml). After a 1-h suckling episode, TH activity in the stalk-median eminence of NAL-treated rats was 4.5-fold greater than controls. Litter weight gains were significantly less in NAL-treated rats during the 1-h suckling episode. These data indicate that the endogenous opioid peptides are an integral component for increasing PRL release in response to suckling and they act to decrease tuberoinfundibular dopaminergic neuronal activity during lactation, in part, by suppressing TH gene expression.
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Affiliation(s)
- L A Arbogast
- Department of Physiology, University of Kansas Medical Center, Kansas City 66160-7401, USA.
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40
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Rubin BS, Lee CE, Ohtomo M, King JC. Luteinizing hormone-releasing hormone gene expression differs in young and middle-aged females on the day of a steroid-induced LH surge. Brain Res 1997; 770:267-76. [PMID: 9372229 DOI: 10.1016/s0006-8993(97)00879-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
LHRH mRNA levels were examined in young and middle-aged female rats at 4 times (10:00 h, 14:00 h, 18:00 h and 20:00 h) on the day of a steroid-induced LH surge by in situ hybridization with a digoxigenin-labeled riboprobe. Young, but not middle-aged females, exhibited dynamic temporal changes in the number of LHRH mRNA positive neurons detected in the organum vasculosum of the lamina terminalis-preoptic area (OVLT-POA) continuum. Specifically, fewer LHRH mRNA positive neurons were detected at 18:00 h compared with the number detected at 14:00 h and 20:00 h (P < 0.01) in the OVLT-POA of young females. All LHRH mRNA positive neurons present in 4 anatomically matched sections through the rostral POA of young and middle-aged animals were digitized for detailed computer-assisted analysis of the hybridization reaction product. The mean hybridization area (P < 0.00025) and integrated optical density per cell (P < 0.006) were reduced in middle-aged compared to young females consistent with a relative age-related decline in LHRH mRNA levels. Moreover, an age-related reduction in cellular and/or regional hybridization area was noted at each of the time points examined (P < 0.05-P < 0.001). These data confirm earlier reports of dynamic changes in LHRH mRNA levels on the day of an LH surge. Furthermore, they support a role for age-related alterations in LHRH gene expression in the disruption of regular estrous cyclicity in middle-aged females.
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Affiliation(s)
- B S Rubin
- Department of Anatomy and Cellular Biology, Tufts University Schools of Medicine, Boston, MA 02111, USA.
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