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Tóth A, Keserű D, Pethő M, Détári L, Bencsik N, Dobolyi Á, Hajnik T. Sleep and local field potential effect of the D2 receptor agonist bromocriptine during the estrus cycle and postpartum period in female rats. Pharmacol Biochem Behav 2024; 239:173754. [PMID: 38537873 DOI: 10.1016/j.pbb.2024.173754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 03/12/2024] [Accepted: 03/22/2024] [Indexed: 04/08/2024]
Abstract
BACKGROUND Pituitary lactotrophs are under tonic dopaminergic inhibitory control and bromocriptine treatment blocks prolactin secretion. METHODS Sleep and local field potential were addressed for 72 h after bromocriptine treatments applied during the different stages of the estrus cycle and for 24 h in the early- and middle postpartum period characterized by spontaneously different dynamics of prolactin release in female rats. RESULTS Sleep changes showed strong dependency on the estrus cycle phase of the drug application. Strongest increase of wakefulness and reduction of slow wave sleep- and rapid eye movements sleep appeared during diestrus-proestrus and middle postpartum treatments. Stronger sleep-wake effects appeared in the dark phase in case of the estrus cycle treatments, but in the light phase in postpartum treatments. Slow wave sleep and REM sleep loss in case of estrus cycle treatments was not compensated at all and sleep loss seen in the first day post-injection was gained further later. In opposition, slow wave sleep loss in the light phase after bromocriptine injections showed compensation in the postpartum period treatments. Bromocriptine treatments resulted in a depression of local field potential delta power during slow wave sleep while an enhancement in beta and gamma power during wakefulness regardless of the treatment timing. CONCLUSIONS These results can be explained by the interplay of dopamine D2 receptor agonism, lack of prolactin release and the spontaneous homeostatic sleep drive being altered in the different stages of the estrus cycle and the postpartum period.
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Affiliation(s)
- Attila Tóth
- In vivo Electrophysiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary.
| | - Dóra Keserű
- In vivo Electrophysiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
| | - Máté Pethő
- In vivo Electrophysiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
| | - László Détári
- In vivo Electrophysiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
| | - Norbert Bencsik
- Cellular Neurobiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
| | - Árpád Dobolyi
- Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
| | - Tünde Hajnik
- In vivo Electrophysiology Research Group, Department of Physiology and Neurobiology, Eötvös Loránd University, Hungary
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Stewart C, Marshall CJ. Seasonality of prolactin in birds and mammals. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:919-938. [PMID: 35686456 PMCID: PMC9796654 DOI: 10.1002/jez.2634] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 04/21/2022] [Accepted: 05/23/2022] [Indexed: 01/07/2023]
Abstract
In most animals, annual rhythms in environmental cues and internal programs regulate seasonal physiology and behavior. Prolactin, an evolutionarily ancient hormone, serves as a molecular correlate of seasonal timing in most species. Prolactin is highly pleiotropic with a wide variety of well-documented physiological effects; in a seasonal context prolactin is known to regulate annual changes in pelage and molt. While short-term homeostatic variation of prolactin secretion is under the control of the hypothalamus, long-term seasonal rhythms of prolactin are programmed by endogenous timers that reside in the pituitary gland. The molecular basis of these rhythms is generally understood to be melatonin dependent in mammals. Prolactin rhythmicity persists for several years in many species, in the absence of hypothalamic signaling. Such evidence in mammals has supported the hypothesis that seasonal rhythms in prolactin derive from an endogenous timer within the pituitary gland that is entrained by external photoperiod. In this review, we describe the conserved nature of prolactin signaling in birds and mammals and highlight its role in regulating multiple diverse physiological systems. The review will cover the current understanding of the molecular control of prolactin seasonality and propose a mechanism by which long-term rhythms may be generated in amniotes.
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Affiliation(s)
- Calum Stewart
- Institute of Biodiversity, Animal Health & Comparative MedicineUniversity of GlasgowGlasgowUK
| | - Christopher J. Marshall
- Institute of Biodiversity, Animal Health & Comparative MedicineUniversity of GlasgowGlasgowUK
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Moeller JS, Bever SR, Finn SL, Phumsatitpong C, Browne MF, Kriegsfeld LJ. Circadian Regulation of Hormonal Timing and the Pathophysiology of Circadian Dysregulation. Compr Physiol 2022; 12:4185-4214. [PMID: 36073751 DOI: 10.1002/cphy.c220018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Circadian rhythms are endogenously generated, daily patterns of behavior and physiology that are essential for optimal health and disease prevention. Disruptions to circadian timing are associated with a host of maladies, including metabolic disease and obesity, diabetes, heart disease, cancer, and mental health disturbances. The circadian timing system is hierarchically organized, with a master circadian clock located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus and subordinate clocks throughout the CNS and periphery. The SCN receives light information via a direct retinal pathway, synchronizing the master clock to environmental time. At the cellular level, circadian rhythms are ubiquitous, with rhythms generated by interlocking, autoregulatory transcription-translation feedback loops. At the level of the SCN, tight cellular coupling maintains rhythms even in the absence of environmental input. The SCN, in turn, communicates timing information via the autonomic nervous system and hormonal signaling. This signaling couples individual cellular oscillators at the tissue level in extra-SCN brain loci and the periphery and synchronizes subordinate clocks to external time. In the modern world, circadian disruption is widespread due to limited exposure to sunlight during the day, exposure to artificial light at night, and widespread use of light-emitting electronic devices, likely contributing to an increase in the prevalence, and the progression, of a host of disease states. The present overview focuses on the circadian control of endocrine secretions, the significance of rhythms within key endocrine axes for typical, homeostatic functioning, and implications for health and disease when dysregulated. © 2022 American Physiological Society. Compr Physiol 12: 1-30, 2022.
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Affiliation(s)
- Jacob S Moeller
- Graduate Group in Endocrinology, University of California, Berkeley, California, USA
| | - Savannah R Bever
- Department of Psychology, University of California, Berkeley, California, USA
| | - Samantha L Finn
- Department of Psychology, University of California, Berkeley, California, USA
| | | | - Madison F Browne
- Department of Psychology, University of California, Berkeley, California, USA
| | - Lance J Kriegsfeld
- Graduate Group in Endocrinology, University of California, Berkeley, California, USA.,Department of Psychology, University of California, Berkeley, California, USA.,Department of Integrative Biology, University of California, Berkeley, California, USA.,The Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
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Morphological and Functional Changes of Pituitary GH and PRL Cells Following Prolonged Exposure of Female Rats to Constant Light. SERBIAN JOURNAL OF EXPERIMENTAL AND CLINICAL RESEARCH 2021. [DOI: 10.2478/sjecr-2019-0063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Light regulates numerous physiological functions including secretion of different hormones. Our aim was to determine morphological and functional changes of the pituitary growth hormone (GH) and prolactin (PRL) producing cells in female rats exposed to constant light regime from the peripubertal to adult period of life. Starting from the thirtieth postnatal day, female Wistar rats were exposed to constant light (600 lx) for the following 95 days. Controls were maintained under the regular laboratory lighting conditions. The GH and PRL cells were immunohistochemically visualized. Changes in cell volumes and volume densities were evaluated by stereology. Concentrations of PRL and GH in circulation were also determined. We detected significant decrease of the GH cell volume and volume density, followed by reduced the GH blood concentration in comparison to the controls. In contrast, PRL cells were larger in size and their volume density was significantly increased when compared to the controls. Accordingly, PRL concentration was elevated. It can be concluded that exposure of female rats to constant light regime, from peripubertal to adult period of life, causes inhibition of the pituitary GH and stimulation of PRL cells.
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Korshunov KS, Blakemore LJ, Trombley PQ. Dopamine: A Modulator of Circadian Rhythms in the Central Nervous System. Front Cell Neurosci 2017; 11:91. [PMID: 28420965 PMCID: PMC5376559 DOI: 10.3389/fncel.2017.00091] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/15/2017] [Indexed: 01/11/2023] Open
Abstract
Circadian rhythms are daily rhythms that regulate many biological processes – from gene transcription to behavior – and a disruption of these rhythms can lead to a myriad of health risks. Circadian rhythms are entrained by light, and their 24-h oscillation is maintained by a core molecular feedback loop composed of canonical circadian (“clock”) genes and proteins. Different modulators help to maintain the proper rhythmicity of these genes and proteins, and one emerging modulator is dopamine. Dopamine has been shown to have circadian-like activities in the retina, olfactory bulb, striatum, midbrain, and hypothalamus, where it regulates, and is regulated by, clock genes in some of these areas. Thus, it is likely that dopamine is essential to mechanisms that maintain proper rhythmicity of these five brain areas. This review discusses studies that showcase different dopaminergic mechanisms that may be involved with the regulation of these brain areas’ circadian rhythms. Mechanisms include how dopamine and dopamine receptor activity directly and indirectly influence clock genes and proteins, how dopamine’s interactions with gap junctions influence daily neuronal excitability, and how dopamine’s release and effects are gated by low- and high-pass filters. Because the dopamine neurons described in this review also release the inhibitory neurotransmitter GABA which influences clock protein expression in the retina, we discuss articles that explore how GABA may contribute to the actions of dopamine neurons on circadian rhythms. Finally, to understand how the loss of function of dopamine neurons could influence circadian rhythms, we review studies linking the neurodegenerative disease Parkinson’s Disease to disruptions of circadian rhythms in these five brain areas. The purpose of this review is to summarize growing evidence that dopamine is involved in regulating circadian rhythms, either directly or indirectly, in the brain areas discussed here. An appreciation of the growing evidence of dopamine’s influence on circadian rhythms may lead to new treatments including pharmacological agents directed at alleviating the various symptoms of circadian rhythm disruption.
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Affiliation(s)
- Kirill S Korshunov
- Program in Neuroscience, Florida State University,Tallahassee, FL, USA.,Department of Biological Science, Florida State University,Tallahassee, FL, USA
| | - Laura J Blakemore
- Program in Neuroscience, Florida State University,Tallahassee, FL, USA.,Department of Biological Science, Florida State University,Tallahassee, FL, USA
| | - Paul Q Trombley
- Program in Neuroscience, Florida State University,Tallahassee, FL, USA.,Department of Biological Science, Florida State University,Tallahassee, FL, USA
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Hypocretin/Orexin Peptides Excite Rat Neuroendocrine Dopamine Neurons through Orexin 2 Receptor-Mediated Activation of a Mixed Cation Current. Sci Rep 2017; 7:41535. [PMID: 28145492 PMCID: PMC5286397 DOI: 10.1038/srep41535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 12/19/2016] [Indexed: 11/11/2022] Open
Abstract
Hypocretin/Orexin (H/O) neurons of the lateral hypothalamus are compelling modulator candidates for the chronobiology of neuroendocrine output and, as a consequence, hormone release from the anterior pituitary. Here we investigate the effects of H/O peptides upon tuberoinfundibular dopamine (TIDA) neurons – cells which control, via inhibition, the pituitary secretion of prolactin. In whole cell recordings performed in male rat hypothalamic slices, application of H/O-A, as well as H/O-B, excited oscillating TIDA neurons, inducing a reversible depolarising switch from phasic to tonic discharge. The H/O-induced inward current underpinning this effect was post-synaptic (as it endured in the presence of tetrodotoxin), appeared to be carried by a Na+-dependent transient receptor potential-like channel (as it was blocked by 2-APB and was diminished by removal of extracellular Na+), and was a consequence of OX2R receptor activation (as it was blocked by the OX2R receptor antagonist TCS OX2 29, but not the OX1R receptor antagonist SB 334867). Application of the hormone, melatonin, failed to alter TIDA membrane potential or oscillatory activity. This first description of the electrophysiological effects of H/Os upon the TIDA network identifies cellular mechanisms that may contribute to the circadian rhythmicity of prolactin secretion.
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Verwey M, Dhir S, Amir S. Circadian influences on dopamine circuits of the brain: regulation of striatal rhythms of clock gene expression and implications for psychopathology and disease. F1000Res 2016; 5. [PMID: 27635233 PMCID: PMC5007753 DOI: 10.12688/f1000research.9180.1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/23/2016] [Indexed: 12/18/2022] Open
Abstract
Circadian clock proteins form an autoregulatory feedback loop that is central to the endogenous generation and transmission of daily rhythms in behavior and physiology. Increasingly, circadian rhythms in clock gene expression are being reported in diverse tissues and brain regions that lie outside of the suprachiasmatic nucleus (SCN), the master circadian clock in mammals. For many of these extra-SCN rhythms, however, the region-specific implications are still emerging. In order to gain important insights into the potential behavioral, physiological, and psychological relevance of these daily oscillations, researchers have begun to focus on describing the neurochemical, hormonal, metabolic, and epigenetic contributions to the regulation of these rhythms. This review will highlight important sites and sources of circadian control within dopaminergic and striatal circuitries of the brain and will discuss potential implications for psychopathology and disease
. For example, rhythms in clock gene expression in the dorsal striatum are sensitive to changes in dopamine release, which has potential implications for Parkinson’s disease and drug addiction. Rhythms in the ventral striatum and limbic forebrain are sensitive to psychological and physical stressors, which may have implications for major depressive disorder. Collectively, a rich circadian tapestry has emerged that forces us to expand traditional views and to reconsider the psychopathological, behavioral, and physiological importance of these region-specific rhythms in brain areas that are not immediately linked with the regulation of circadian rhythms.
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Affiliation(s)
- Michael Verwey
- Center for Studies in Behavioural Neurobiology, FRQS Groupe de Recherche en Neurobiologie Comportementale, Concorida University, Montreal, Quebec, Canada
| | | | - Shimon Amir
- Center for Studies in Behavioural Neurobiology, FRQS Groupe de Recherche en Neurobiologie Comportementale, Concorida University, Montreal, Quebec, Canada
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Mendoza J, Challet E. Circadian insights into dopamine mechanisms. Neuroscience 2014; 282:230-42. [PMID: 25281877 DOI: 10.1016/j.neuroscience.2014.07.081] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 07/22/2014] [Accepted: 07/24/2014] [Indexed: 01/11/2023]
Abstract
Almost every physiological or behavioral process in mammals follows rhythmic patterns, which depend mainly on a master circadian clock located in the hypothalamic suprachiasmatic nucleus (SCN). The dopaminergic (DAergic) system in the brain is principally implicated in motor functions, motivation and drug intake. Interestingly, DA-related parameters and behaviors linked to the motivational and arousal states, show daily rhythms that could be regulated by the SCN or by extra-SCN circadian oscillator(s) modulating DAergic systems. Here we examine what is currently understood about the anatomical and functional central multi-oscillatory circadian system, highlighting how the main SCN clock communicates timing information with other brain clocks to regulate the DAergic system and conversely, how DAergic cues may have feedback effects on the SCN. These studies give new insights into the role of the brain circadian system in DA-related neurologic pathologies, such as Parkinson's disease, attention deficit/hyperactive disorder and drug addiction.
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Affiliation(s)
- J Mendoza
- Institute of Cellular and Integrative Neurosciences, CNRS UPR-3212, University of Strasbourg, 5 rue Blaise Pascal, 67084 Strasbourg cedex, France.
| | - E Challet
- Institute of Cellular and Integrative Neurosciences, CNRS UPR-3212, University of Strasbourg, 5 rue Blaise Pascal, 67084 Strasbourg cedex, France
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Tonsfeldt KJ, Chappell PE. Clocks on top: the role of the circadian clock in the hypothalamic and pituitary regulation of endocrine physiology. Mol Cell Endocrinol 2012; 349:3-12. [PMID: 21787834 PMCID: PMC3242828 DOI: 10.1016/j.mce.2011.07.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 07/01/2011] [Accepted: 07/01/2011] [Indexed: 01/24/2023]
Abstract
Recent strides in circadian biology over the last several decades have allowed researchers new insight into how molecular circadian clocks influence the broader physiology of mammals. Elucidation of transcriptional feedback loops at the heart of endogenous circadian clocks has allowed for a deeper analysis of how timed cellular programs exert effects on multiple endocrine axes. While the full understanding of endogenous clocks is currently incomplete, recent work has re-evaluated prior findings with a new understanding of the involvement of these cellular oscillators, and how they may play a role in constructing rhythmic hormone synthesis, secretion, reception, and metabolism. This review addresses current research into how multiple circadian clocks in the hypothalamus and pituitary receive photic information from oscillators within the hypothalamic suprachiasmatic nucleus (SCN), and how resultant hypophysiotropic and pituitary hormone release is then temporally gated to produce an optimal result at the cognate target tissue. Special emphasis is placed not only on neural communication among the SCN and other hypothalamic nuclei, but also how endogenous clocks within the endocrine hypothalamus and pituitary may modulate local hormone synthesis and secretion in response to SCN cues. Through evaluation of a larger body of research into the impact of circadian biology on endocrinology, we can develop a greater appreciation into the importance of timing in endocrine systems, and how understanding of these endogenous rhythms can aid in constructing appropriate therapeutic treatments for a variety of endocrinopathies.
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Affiliation(s)
- Karen J Tonsfeldt
- Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, United States
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Barclay JL, Tsang AH, Oster H. Interaction of central and peripheral clocks in physiological regulation. PROGRESS IN BRAIN RESEARCH 2012; 199:163-181. [DOI: 10.1016/b978-0-444-59427-3.00030-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Meza E, Waliszewski SM, Caba M. Circadian nursing induces PER1 protein in neuroendocrine tyrosine hydroxylase neurones in the rabbit doe. J Neuroendocrinol 2011; 23:472-80. [PMID: 21564346 DOI: 10.1111/j.1365-2826.2011.02138.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rabbit does nurse their pups once a day with circadian periodicity and pups ingest up to 35% of their body weight in milk in < 5 min. In the doe, there is a massive release of prolactin. We hypothesised that periodic suckling synchronises dopaminergic populations that control prolactin secretion. We explored this by immunohistochemical colocalisation of PER1 protein, the product of the clock gene Per1 on tyrosine hydroxylase (TH) cells in three dopaminergic populations: tuberoinfundibular dopaminergic (TIDA), periventricular hypophyseal dopaminergic (PHDA) and incertohypothalamic dopaminergic (IHDA) cells. PER1/TH colocalisation was explored every 4 h through a complete 24-h cycle at postpartum day 7 in does that nursed their pups either at 10.00 h (ZT03) or at 02.00 h (ZT19; ZT0 = 07.00 h, time of lights on). Nonpregnant, nonlactating females were used as controls. In control females, there was a rhythm of PER1 that peaks at ZT15. By contrast, in nursed does, the PER1 peak shifted in parallel to scheduled nursing in TIDA and PHDA cells but not in IHDA cells, which are not related to the control of prolactin. Next, we determined that the absence of suckling for 48 h significantly decreases the number of PER1/TH colocalised cells in PHDA but not TIDA cells. Locomotor behaviour in control subjects was maximal at around the time of lights on but, in nursed females, shifted at around the time of scheduled nursing. Finally, in the suprachiasmatic nucleus, there is a maximal expression of PER1 at ZT11 in the three groups. However, this maximal expression was significantly lower in the nursed groups in relation to the control group and in the groups deprived of nursing for 48 h. We conclude that suckling synchronises dopaminergic cells related to the control of prolactin and appears to be a nonphotic stimulus for the suprachiasmatic nucleus.
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Affiliation(s)
- E Meza
- Centro de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Ver., México
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Leite CM, Ribeiro AB, Szawka RE, Anselmo-Franci JA. Activity of hypothalamic dopaminergic neurones during the day of oestrus: involvement in prolactin secretion. J Neuroendocrinol 2010; 22:1052-60. [PMID: 20722974 DOI: 10.1111/j.1365-2826.2010.02057.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A secretory surge of prolactin occurs on the afternoon of oestrus in cycling rats. Pituitary prolactin is inhibited by dopamine. We evaluated the activity of the neuroendocrine dopaminergic neurones during oestrus and dioestrus, as determined by dopaminergic activity in the median eminence and neurointermediate lobe of the pituitary, as well as Fos-related antigen expression in tyrosine hydroxylase (TH)-immunoreactive (ir) neurones of the arcuate nucleus (ARC) and periventricular nucleus (Pe). During oestrus, the 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence decreased at 16.00 h, coinciding with the increase in plasma prolactin levels. Similarly, the expression of Fos-related antigen in TH-ir neurones of Pe and rostral-, dorsomedial- and caudal-ARC also decreased at 16.00 h. On dioestrus, 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence and Fos-related antigen expression in TH-ir neurones of Pe and rostral-ARC decreased at 18.00 h, whereas prolactin levels were unaltered. No variation in dopaminergic activity was found in the neurointermediate lobe of the pituitary on either oestrus or dioestrus. The number of TH-ir neurones in the ARC and parameters of dopaminergic activity were found to be generally lower on oestrus compared to dioestrus. The transitory decrease in the activity of neuroendocrine dopaminergic neurones temporally associated with the prolactin surge on the afternoon of oestrus suggests a role for dopamine in the generation of the oestrous prolactin surge.
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Affiliation(s)
- C M Leite
- Laboratório de Neuroendocrinologia, Departamento de Morfologia, Estomatologia e Fisiologia, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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Poletini MO, Kennett JE, McKee DT, Freeman ME. Central clock regulates the cervically stimulated prolactin surges by modulation of dopamine and vasoactive intestinal polypeptide release in ovariectomized rats. Neuroendocrinology 2010; 91:179-88. [PMID: 19887760 PMCID: PMC2853580 DOI: 10.1159/000254379] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 07/15/2009] [Indexed: 01/25/2023]
Abstract
BACKGROUND/AIMS Cervical stimulation induces a circadian rhythm of prolactin secretion and antiphase dopamine release. The suprachiasmatic nucleus (SCN) controls this rhythm, and we propose that it does so through clock gene expression within the SCN. METHODS To test this hypothesis, serial blood samples were taken from animals injected with an antisense deoxyoligonucleotide cocktail for clock genes (generated against the 5' transcription start site and 3' cap site of per1, per2, and clock mRNA) or with a random-sequence deoxyoligonucleotide in the SCN. To determine whether disruption of clock genes in the SCN compromises the neural mechanism controlling prolactin secretion, we sacrificed another group of rats (under the same treatments) at 12.00 or 17.00 h. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured using HPLC/electrochemical detection in the median eminence as well as the intermediate and the neural lobe of the pituitary gland, and the DOPAC:dopamine ratio was used as an index of dopamine activity. Vasoactive intestinal polypeptide (VIP) content was determined in tissue punches of the SCN and paraventricular nucleus (PVN), an SCN efferent. RESULTS Treatment with clock gene antisense deoxyoligonucleotide cocktail abolished both the diurnal and nocturnal prolactin surges induced by cervical stimulation. This treatment abolished the antiphase relationship established by cervical stimulation between dopamine neuronal activity and prolactin secretion. Also, VIP content increased in the SCN and decreased in the PVN. CONCLUSION These results suggest that the SCN clock determines the circadian rhythm of prolactin secretion in cervically stimulated rats by regulating dopamine neuronal activity and VIP inputs to the PVN.
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Affiliation(s)
- Maristela O. Poletini
- Biological Science and Program in Neuroscience, Florida State University, Tallahassee, Fla., USA
- Neuroscience and Behavior Program and Center for Neuroendocrine Studies, University of Massachusetts, Amherst, Mass., USA
| | - Jessica E. Kennett
- Biological Science and Program in Neuroscience, Florida State University, Tallahassee, Fla., USA
| | - De'Nise T. McKee
- Biological Science and Program in Neuroscience, Florida State University, Tallahassee, Fla., USA
| | - Marc E. Freeman
- Biological Science and Program in Neuroscience, Florida State University, Tallahassee, Fla., USA
- *Marc E. Freeman, Department of Biological Science, Florida State University, Tallahassee, FL 32306 (USA), Tel. +1 850 644 3896, Fax +1 850 644 4583, E-Mail
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Ramanathan C, Nunez AA, Smale L. Daily rhythms in PER1 within and beyond the suprachiasmatic nucleus of female grass rats (Arvicanthis niloticus). Neuroscience 2008; 156:48-58. [PMID: 18692118 PMCID: PMC2758417 DOI: 10.1016/j.neuroscience.2008.07.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 06/02/2008] [Accepted: 07/03/2008] [Indexed: 11/30/2022]
Abstract
Although circadian rhythms of males and females are different in a variety of ways in many species, their mechanisms have been primarily studied in males. Furthermore, rhythms are dramatically different in diurnal and nocturnal animals but have been studied predominantly in nocturnal ones. In the present study, we examined rhythms in one element of the circadian oscillator, the PER1 protein, in a variety of cell populations in brains of diurnal female grass rats. Every 4 h five adult female grass rats kept on a 12-h light/dark (LD) cycle were perfused and their brains were processed for immunohistochemical detection of PER1. Numbers of PER1-labeled cells were rhythmic not only within the suprachiasmatic nucleus (SCN), the locus of the primary circadian clock in mammals, but also in the peri-suprachiasmatic region, the oval nucleus of the bed nucleus of the stria terminalis, the central amygdala, and the nucleus accumbens. In addition, rhythms were detected within populations of neuroendocrine cells that contain tyrosine hydroxylase. The phase of the rhythm within the SCN was advanced compared with that seen previously in male grass rats. Rhythms beyond the SCN were varied and different from those seen in most nocturnal species, suggesting that signals originating in the SCN are modified by its direct and/or indirect targets in different ways in nocturnal and diurnal species.
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Affiliation(s)
- C. Ramanathan
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - A. A. Nunez
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - L. Smale
- Department of Psychology, Michigan State University, East Lansing, MI 48824, USA
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
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McKee DT, Poletini MO, Bertram R, Freeman ME. Oxytocin action at the lactotroph is required for prolactin surges in cervically stimulated ovariectomized rats. Endocrinology 2007; 148:4649-57. [PMID: 17615142 PMCID: PMC2085361 DOI: 10.1210/en.2007-0646] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cervical stimulation induces two daily rhythmic prolactin surges, nocturnal and diurnal, which persist for several days. We have shown that a bolus injection of oxytocin initiates a similar prolactin rhythm, which persists despite low levels of oxytocin after injection. This suggests that oxytocin may trigger the cervical stimulation-induced rhythmic prolactin surges. To investigate this hypothesis, we infused an oxytocin antagonist that does not cross the blood-brain barrier for 24 h before and after cervical stimulation and measured serum prolactin. We also measured dopaminergic neuronal activity because mathematical modeling predicted that this activity would be low in the presence of the oxytocin antagonist. We thus tested this hypothesis by measuring dopaminergic neuronal activity in the tuberoinfundibular, periventricular hypophyseal, and tuberohypophyseal dopaminergic neurons. Infusion of oxytocin antagonist before cervical stimulation abolished prolactin surges, and infusion of oxytocin antagonist after cervical stimulation abolished the diurnal and significantly decreased the nocturnal surges of prolactin. The rhythmic prolactin surges returned after the clearance of the oxytocin antagonist. Hypothalamic dopaminergic activity was elevated in antiphase with prolactin surges, and the antiphase elevation was abolished by the oxytocin antagonist in the tuberoinfundibular and tuberohypophyseal dopaminergic neurons, consistent with the mathematical model. These findings suggest that oxytocin is a physiologically relevant prolactin-releasing factor. However, the cervical stimulation-induced prolactin surges are maintained even in the absence of oxytocin actions at the lactotroph, which strongly suggests the maintenance of prolactin surges are not dependent upon oxytocin actions at the pituitary gland.
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Affiliation(s)
- De'Nise T McKee
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA
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Guilding C, Piggins HD. Challenging the omnipotence of the suprachiasmatic timekeeper: are circadian oscillators present throughout the mammalian brain? Eur J Neurosci 2007; 25:3195-216. [PMID: 17552989 DOI: 10.1111/j.1460-9568.2007.05581.x] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The suprachiasmatic nucleus of the hypothalamus (SCN) is the master circadian pacemaker or clock in the mammalian brain. Canonical theory holds that the output from this single, dominant clock is responsible for driving most daily rhythms in physiology and behaviour. However, important recent findings challenge this uniclock model and reveal clock-like activities in many neural and non-neural tissues. Thus, in addition to the SCN, a number of areas of the mammalian brain including the olfactory bulb, amygdala, lateral habenula and a variety of nuclei in the hypothalamus, express circadian rhythms in core clock gene expression, hormone output and electrical activity. This review examines the evidence for extra-SCN circadian oscillators in the mammalian brain and highlights some of the essential properties and key differences between brain oscillators. The demonstration of neural pacemakers outside the SCN has wide-ranging implications for models of the circadian system at a whole-organism level.
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Affiliation(s)
- Clare Guilding
- 3.614 Stopford Building, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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Mahoney MM, Ramanathan C, Smale L. Tyrosine hydroxylase positive neurons and their contacts with vasoactive intestinal polypeptide-containing fibers in the hypothalamus of the diurnal murid rodent, Arvicanthis niloticus. J Chem Neuroanat 2007; 33:131-9. [PMID: 17368836 DOI: 10.1016/j.jchemneu.2007.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 01/28/2007] [Accepted: 02/03/2007] [Indexed: 11/19/2022]
Abstract
Diurnal and nocturnal animals differ with respect to the timing of a host of behavioral and physiological events including those associated with neuroendocrine functions, but the neural bases of these differences are poorly understood. In nocturnal species, rhythms in tyrosine hydroxylase-containing (TH+) neurons in the hypothalamus appear to be responsible for rhythms in prolactin secretion. Here we investigated TH+ cells in a diurnal rodent (Arvicanthis niloticus, the unstriped Nile grass rat), and comparing them with those of a nocturnal rodent (Rattus norvegicus, Sprague-Dawley rat). We also examined relationships between TH+ cells and fibers containing vasoactive intestinal polypeptide (VIP) that are thought to originate from cells in the suprachiasmatic nucleus (SCN), the site of the primary circadian clock in mammals. The distribution of TH+ neurons was very similar in the two species except for a population of cells in the basal forebrain that was only present in grass rats. Fibers containing VIP appeared to contact neuroendocrine TH+ cells in both species. These data suggest that, though there may be subtle species differences, temporal information is likely to be carried along the same direct pathways from the SCN to the TH+ neurons in day- and night-active species.
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Affiliation(s)
- Megan M Mahoney
- Environmental Health Sciences Program and Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1109, USA.
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Sellix MT, Egli M, Poletini MO, McKee DT, Bosworth MD, Fitch CA, Freeman ME. Anatomical and functional characterization of clock gene expression in neuroendocrine dopaminergic neurons. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1309-23. [PMID: 16373438 PMCID: PMC1457054 DOI: 10.1152/ajpregu.00555.2005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oscillations of gene expression and physiological activity in suprachiasmatic nucleus (SCN) neurons result from autoregulatory feedback loops of circadian clock gene transcription factors. In the present experiment, we have determined the pattern of PERIOD1 (PER1), PERIOD2 (PER2), and CLOCK expression within neuroendocrine dopaminergic (DAergic) neurons (NDNs) of ovariectomized (OVX) rats. We have also determined the effects of per1, per2, and clock mRNA knockdown in the SCN with antisense deoxyoligonucleotides (AS-ODN) on DA release from NDNs. Diurnal rhythms of PER1 and PER2 expression in tuberoinfundibular DAergic (TIDA) and periventricular hypophyseal DAergic (PHDA) neurons, peaked at circadian time (CT)18 and CT12, respectively. Rhythms of PER1 expression in tuberhypophyseal neuroendocrine DAergic (THDA) neurons were undetectable. Rhythms of PER2 expression were found in all three populations of NDNs, with greater levels of PER2 expression between CT6 and CT12. AS-ODN injections differentially affected DA turnover in the axon terminals of the median eminence (ME), neural lobe (NL) and intermediate lobe (IL) of the pituitary gland, resulting in a significant decrease in DA release in the early subjective night in the ME (TIDA), a significant increase in DA release at the beginning of the day in the IL (PHDA), and no effect in the NL (THDA). AS-ODN-treatment induced a rhythm of DA concentration in the anterior lobe, with greater DA levels in the middle of the day. These data suggest that clock gene expression, particularly PER1 and PER2, within NDNs may act to modulate diurnal rhythms of DA release from NDNs in the OVX rat.
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Affiliation(s)
- Michael T Sellix
- Department of Biological Science, Florida State Univ., Tallahassee, Florida, USA
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Egli M, Bertram R, Toporikova N, Sellix MT, Blanco W, Freeman ME. Prolactin secretory rhythm of mated rats induced by a single injection of oxytocin. Am J Physiol Endocrinol Metab 2006; 290:E566-72. [PMID: 16467487 PMCID: PMC1543713 DOI: 10.1152/ajpendo.00427.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Mating or vaginocervical stimulation [copulatory stimulus (CS)] induces two daily surges of the hormone prolactin (PRL) in rats. This unique secretory pattern of PRL surges is characteristic for the first half of pregnancy and is also present in ovariectomized (OVX) rats. Studies have shown that CS additionally provokes an acute release of the hormone oxytocin (OT). In this study, we tested whether a single injection of OT (iv) is sufficient to initiate the PRL secretion pattern of OVX/CS rats. Furthermore, we measured the 24-h profile of dopamine (DA) content in the anterior lobe of the pituitary gland, because DA is the major inhibitory factor of PRL secretion. The results indicated that a single injection of OT induces a PRL secretory rhythm and a DA release pattern similar to that initiated by CS. Immunocytochemical investigation showed that particular OTergic neurons in the hypothalamus express receptors for PRL, as well as for vasoactive intestinal polypeptide, which indicates an involvement in generating the PRL rhythm and entraining it to the ambient photoperiod. On the basis of this study, we suggest that the PRL-DA inhibitory feedback loop between lactotrophs and DAergic neurons plays a crucial role in generating the oscillatory PRL secretion pattern in CS rats. A timing signal, likely provided by the hypothalamic suprachiasmatic nucleus, entrains the autonomous PRL oscillation to a particular time of day. Mathematical modeling was used to illustrate the proposed network function. The experimental results further suggest an additional feedback mechanism in which certain hypothalamic OTergic neurons are influenced by PRL.
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Affiliation(s)
- Marcel Egli
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
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Sellix MT, Egli M, Henderson RP, Freeman ME. Ovarian steroid hormones modulate circadian rhythms of neuroendocrine dopaminergic neuronal activity. Brain Res 2004; 1005:164-81. [PMID: 15044075 DOI: 10.1016/j.brainres.2004.01.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2004] [Indexed: 11/19/2022]
Abstract
Dopamine (DA) is the primary inhibitor of prolactin (PRL) secretion. Three populations of neuroendocrine dopaminergic neurons (NDNs) designated tuberoinfundibular (TIDA), tuberohypophyseal (THDA) and periventricular hypophyseal DAergic (PHDA) neurons regulate PRL secretion. Given that ovarian steroids modulate both DA release and PRL secretion independently, we characterized the role of steroid hormones in coupling rhythmic NDN activity and PRL secretion. OVX rats under a standard 12:12 L:D cycle (L:D), constant dark (DD), or a 6-h phase-delayed L:D cycle (pdL:D) were treated with Estradiol-17beta (E) or E and Progesterone (E+P). NDN activity, defined by DA:DOPAC ratio in nerve terminals, was determined by HPLC-EC. E or E+P stimulated PRL surges in L:D that persisted under DD. In TIDA neurons, E or E+P treatment reduced the amount of DA released under L:D and DD and advanced the rhythm of DA turnover. E and E+P treatment reduced THDA and PHDA neuron activity under L:D, but did not affect these rhythms under DD. Circadian rhythms of PRL, corticosterone and DA turnover in NDN terminals from steroid treated rats entrained to a pdL:D cycle within 7 days. Therefore, ovarian steroids differentially adjust the timing and magnitude of NDN activity to facilitate coupling of DA release and PRL secretion.
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Affiliation(s)
- Michael T Sellix
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA
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Ribelayga C, Wang Y, Mangel SC. A circadian clock in the fish retina regulates dopamine release via activation of melatonin receptors. J Physiol 2003; 554:467-82. [PMID: 14565990 PMCID: PMC1664774 DOI: 10.1113/jphysiol.2003.053710] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Although many biochemical, morphological and physiological processes in the vertebrate retina are controlled by a circadian (24 h) clock, the location of the clock and how the clock alters retinal function are unclear. For instance, several observations have suggested that dopamine, a retinal neuromodulator, may play an important role in retinal rhythmicity but the link between dopamine and a clock located within or outside the retina remains to be established. We found that endogenous dopamine release from isolated goldfish retinae cultured in continuous darkness for 56 h clearly exhibited a circadian rhythm with high values during the subjective day. The continuous presence of melatonin (1 nM) in the culture medium abolished the circadian rhythm of dopamine release and kept values constantly low and equal to the night-time values. The selective melatonin antagonist luzindole (1 microM) also abolished the dopamine rhythm but the values were high and equal to the daytime values. Melatonin application during the late subjective day introduced rod input and reduced cone input to fish cone horizontal cells, a state usually observed during the subjective night. In contrast, luzindole application during the subjective night decreased rod input and increased cone input. Prior application of dopamine or spiperone, a selective dopamine D(2)-like antagonist, blocked the above effects of melatonin and luzindole, respectively. These findings indicate that a circadian clock in the vertebrate retina regulates dopamine release by the activation of melatonin receptors and that endogenous melatonin modulates rod and cone pathways through dopamine-mediated D(2)-like receptor activation.
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Affiliation(s)
- Christophe Ribelayga
- Department of Neurobiology, Civitan International Research Center, University of Alabama School of Medicine, Birmingham, AL 35294, USA
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