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Ugrumov MV. Hypothalamic neurons fully or partially expressing the dopaminergic phenotype: development, distribution, functioning and functional significance. A review. Front Neuroendocrinol 2024; 75:101153. [PMID: 39128801 DOI: 10.1016/j.yfrne.2024.101153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 08/06/2024] [Accepted: 08/06/2024] [Indexed: 08/13/2024]
Abstract
The hypothalamus is a key link in neuroendocrine regulations, which are provided by neuropeptides and dopamine. Until the late 1980 s, it was believed that, along with peptidergic neurons, hypothalamus contained dopaminergic neurons. Over time, it has been shown that besides dopaminergic neurons expressing the dopamine transporter and dopamine-synthesizing enzymes - tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) - the hypothalamus contains neurons expressing only TH, only AADC, both enzymes or only dopamine transporter. The end secretory product of TH neurons is L-3,4-dihydroxyphenylalanine, while that of AADC neurons and bienzymatic neurons lacking the dopamine transporter is dopamine. During ontogenesis, especially in the perinatal period, monoenzymatic neurons predominate in the hypothalamic neuroendocrine centers. It is assumed that L-3,4-dihydroxyphenylalanine and dopamine are released into the neuropil, cerebral ventricles, and blood vessels, participating in the regulation of target cell differentiation in the perinatal period and the functioning of target cells in adulthood.
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Affiliation(s)
- Michael V Ugrumov
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia.
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Krysiak R, Kowalcze K, Okopień B. Sexual function and depressive symptoms in young women with hypoprolactinaemia. Clin Endocrinol (Oxf) 2020; 93:482-488. [PMID: 32654174 DOI: 10.1111/cen.14283] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Dopamine agonist treatment may result in hypersexuality in men. The aim of this study was to investigate for the first time female sexual functioning and depressive symptoms in women with very low prolactin levels. DESIGN A prospective case-control study. PATIENTS AND MEASUREMENTS The study population consisted of three age-matched groups of young women with normal, regular menstrual cycles: 15 subjects with cabergoline-induced hypoprolactinaemia (group A), 25 cabergoline-treated individuals with prolactin levels within the reference range (group B) and 30 dopamine agonist-naïve women with normoprolactinemia. Because of low prolactin levels, the dose of cabergoline in group A (but not in group B) was then reduced. Apart from measuring serum levels of prolactin, testosterone, sex hormone-binding globulin, dehydroepiandrosterone sulphate, estradiol and gonadotropins, at the beginning of the study and 6 months later, all included women filled in questionnaires evaluating female sexual function (FSFI) and depressive symptoms (BDI-II). RESULTS At the beginning of the study, there were no differences between groups B and C in the mean total FSFI score, all domain scores and in the BDI-II score. In group A, the total FSFI score and domain scores for desire and arousal were lower, while the BDI-II score was higher than in the remaining study groups. Compared with groups of B and C, women with cabergoline-induced hypoprolactinaemia were also characterized by lower total testosterone levels and lower values of the free androgen index. Cabergoline dose reduction normalized the FSFI score, desire, arousal, the BDI-II score, as well as normalized prolactin, total testosterone and the free androgen index. CONCLUSIONS The obtained results suggest that dopamine agonist-induced hypoprolactinaemia impairs sexual functioning and well-being in young women, as well as that these disturbances are secondary to low prolactin levels, not to specific properties of cabergoline.
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Affiliation(s)
- Robert Krysiak
- Department of Internal Medicine and Clinical Pharmacology, Medical University of Silesia, Katowice, Poland
| | - Karolina Kowalcze
- Department of Pediatrics in Bytom, School of Health Sciences in Katowice, Medical University of Silesia, Katowice, Poland
| | - Bogusław Okopień
- Department of Internal Medicine and Clinical Pharmacology, Medical University of Silesia, Katowice, Poland
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Pronina TS, Dil’mukhametova LK, Kurtova AI, Ugrumov MV. Synthesis of Dopamine by Non-Dopaminergic Neurons of the Rat Tuberoinfundibular System during Ontogeny. NEUROCHEM J+ 2019. [DOI: 10.1134/s1819712419040032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ugryumov MV. Dopamine Synthesis by Non-Dopaminergic Neurons as an Effective Mechanism of Neuroplasticity. NEUROCHEM J+ 2018. [DOI: 10.1134/s1819712418040086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Sex-dependent effect of metformin on hypothalamic-pituitary-thyroid axis activity in patients with subclinical hypothyroidism. Pharmacol Rep 2016; 68:1115-1119. [PMID: 27588386 DOI: 10.1016/j.pharep.2016.07.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 06/27/2016] [Accepted: 07/14/2016] [Indexed: 12/18/2022]
Abstract
BACKGROUND Metformin was found to reduce elevated serum thyrotropin levels. No previous study has compared the effect of this drug on serum levels of thyrotropin and thyroid hormones between men and women. METHODS The study included 23 women and 12 men with subclinical hypothyroidism, who because of coexisting diabetes or impaired fasting glucose were treated with metformin (1.7-3.0g daily). Fasting plasma glucose levels, the homeostatic model assessment 1 of insulin resistance ratio (HOMA1-IR), glycated hemoglobin, serum levels of thyrotropin, free and total thyroid hormones and prolactin, as well as thyroid peroxidase and thyroglobulin antibodies were assessed at baseline and after 4 months of metformin treatment. RESULTS Baseline serum levels of thyrotropin, free thyroxine and free triiodothyronine, as well as a percentage of patients with positive thyroid peroxidase and thyroglobulin antibodies were comparable in both sexes. Metformin treatment reduced plasma glucose and insulin resistance, irrespective of the gender. However, only in women, metformin decreased serum thyrotropin levels. Neither in men nor in women, metformin affected serum levels of thyroid hormone and prolactin, as well as in the subgroups of patients with thyroiditis thyroid antibody titers. CONCLUSIONS The obtained results suggest that sex may determine the effect of metformin on hypothalamic-pituitary-thyroid axis activity.
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Ugrumov M, Taxi J, Pronina T, Kurina A, Sorokin A, Sapronova A, Calas A. Neurons expressing individual enzymes of dopamine synthesis in the mediobasal hypothalamus of adult rats: functional significance and topographic interrelations. Neuroscience 2014; 277:45-54. [PMID: 24997271 DOI: 10.1016/j.neuroscience.2014.06.051] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 06/20/2014] [Accepted: 06/24/2014] [Indexed: 11/30/2022]
Abstract
Besides dopaminergic (DA-ergic) neurons having all enzymes of DA synthesis, tyrosine hydroxylase (TH) and aromatic l-amino acid decarboxylase (AADC), "monoenzymatic" neurons expressing only one of them were found in the brain, mostly in the mediobasal hypothalamus (MBH). The aim of this study was to test our hypothesis that DA is synthesized by monoenzymatic neurons, i.e. l-3,4-dihydroxyphenylalanine (l-DOPA), which produced in the monoenzymatic TH neurons is transported in the monoenzymatic AADC neurons for DA synthesis. Incubation of MBH in Krebs-Ringer solution with l-leucine, a competitive inhibitor of l-DOPA uptake, was used to prevent a hypothetical l-DOPA capture into AADC-containing neurons. Incubation of the substantia nigra containing DA-ergic neurons under the same conditions served as the control. According to our data, the l-leucine administration provoked a decrease of DA concentration in MBH and in the incubation medium but not in the substantia nigra and respective incubation medium, showing a decrease of cooperative synthesis of DA in MBH. This conclusion was supported by an observation of higher concentration of l-DOPA in the incubation medium under perfusion of MBH with Krebs-Ringer solution containing tolcapone, an inhibitor of catechol-O-methyltransferase, and l-leucine than under perfusion with the same solution, but without l-leucine. Functional interaction between monoenzymatic TH and AADC neurons was indirectly confirmed by finding in electron microscopy their close relations in MBH. Besides monoenzymatic AADC neurons, any AADC-possessing neurons, catecholaminergic and serotoninergic, apparently, could participate in DA synthesis together with monoenzymatic TH neurons. This idea was confirmed by the observation of close topographic relations between monoenzymatic TH neurons and those containing both enzymes, i.e. DA-ergic, noradrenergic or adrenergic. Thus, monoenzymatic neurons possessing TH or AADC and being in close topographic relations can synthesize DA in cooperation.
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Affiliation(s)
- M Ugrumov
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov St., Moscow 119334, Russia.
| | - J Taxi
- Laboratoire de Pathophysiologie des maladies du système nervoux central, UMR5 INSERM 952, IFR 83, Université P. et M. Curie, 7 quai St. Bernard, 75252 Paris Cedex 05, France
| | - T Pronina
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov St., Moscow 119334, Russia
| | - A Kurina
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov St., Moscow 119334, Russia
| | - A Sorokin
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov St., Moscow 119334, Russia; Laboratoire de Pathophysiologie des maladies du système nervoux central, UMR5 INSERM 952, IFR 83, Université P. et M. Curie, 7 quai St. Bernard, 75252 Paris Cedex 05, France
| | - A Sapronova
- Laboratory of Neural and Neuroendocrine Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov St., Moscow 119334, Russia
| | - A Calas
- IINS, UMR CNRS 5297, Université Bordeaux Segalen, 146 rue Léo Saignat, 33076 Bordeaux-Cedex, France
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Goebrecht GKE, Kowtoniuk RA, Kelly BG, Kittelberger JM. Sexually-dimorphic expression of tyrosine hydroxylase immunoreactivity in the brain of a vocal teleost fish (Porichthys notatus). J Chem Neuroanat 2014; 56:13-34. [PMID: 24418093 DOI: 10.1016/j.jchemneu.2014.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 01/04/2014] [Accepted: 01/04/2014] [Indexed: 12/23/2022]
Abstract
Vocal communication has emerged as a powerful model for the study of neural mechanisms of social behavior. Modulatory neurochemicals postulated to play a central role in social behavior, related to motivation, arousal, incentive and reward, include the catecholamines, particularly dopamine and noradrenaline. Many questions remain regarding the functional mechanisms by which these modulators interact with sensory and motor systems. Here, we begin to address these questions in a model system for vocal and social behavior, the plainfin midshipman fish (Porichthys notatus). We mapped the distribution of immunoreactivity for the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in the midshipman brain. The general pattern of TH(+) cell groups in midshipman appears to be highly conserved with other teleost fish, with a few exceptions, including the apparent absence of pretectal catecholamine cells. Many components of the midshipman vocal and auditory systems were innervated by TH(+) fibers and terminals, including portions of the subpallial area ventralis, the preoptic complex, and the anterior hypothalamus, the midbrain periaqueductal gray and torus semicircularis, several hindbrain auditory nuclei, and parts of the hindbrain vocal pattern generator. These areas thus represent potential sites for catecholamine modulation of vocal and/or auditory behavior. To begin to test functionally whether catecholamines modulate vocal social behaviors, we hypothesized that male and female midshipman, which are sexually dimorphic in both their vocal-motor repertoires and in their responses to hearing conspecific vocalizations, should exhibit sexually dimorphic expression of TH immunoreactivity in their vocal and/or auditory systems. We used quantitative immunohistochemical techniques to test this hypothesis across a number of brain areas. We found significantly higher levels of TH expression in male midshipman relative to females in the TH cell population in the paraventricular organ of the diencephalon and in the TH-innervated torus semicircularis, the main teleost midbrain auditory structure. The torus semicircularis has been implicated in sexually dimorphic behavioral responses to conspecific vocalizations. Our data thus support the general idea that catecholamines modulate vocal and auditory processing in midshipman, and the specific hypothesis that they shape sexually dimorphic auditory responses in the auditory midbrain.
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Affiliation(s)
- Geraldine K E Goebrecht
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - Robert A Kowtoniuk
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - Brenda G Kelly
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - J Matthew Kittelberger
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
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Ugrumov MV. Brain neurons partly expressing dopaminergic phenotype: location, development, functional significance, and regulation. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2013; 68:37-91. [PMID: 24054140 DOI: 10.1016/b978-0-12-411512-5.00004-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In addition to catecholaminergic neurons possessing all the enzymes of catecholamine synthesis and the specific membrane transporters, neurons partly expressing the catecholaminergic phenotype have been found a quarter of a century ago. Most of them express individual enzymes of dopamine (DA) synthesis, tyrosine hydroxylase (TH), or aromatic l-amino acid decarboxylase (AADC), lacking the DA membrane transporter and the vesicular monoamine transporter, type 2. These so-called monoenzymatic neurons are widely distributed throughout the brain in ontogenesis and adulthood being in some brain regions even more numerous than dopaminergic (DA-ergic) neurons. Individual enzymes of DA synthesis are expressed in these neurons continuously or transiently in norm and pathology. It has been proven that monoenzymatic TH neurons and AADC neurons are capable of producing DA in cooperation. It means that l-3,4-dihydroxyphenylalanine (l-DOPA) synthesized from l-tyrosine in monoenzymatic TH neurons is transported to monoenzymatic AADC neurons for DA synthesis. Such cooperative synthesis of DA is considered as a compensatory reaction under a failure of DA-ergic neurons, for example, in neurodegenerative diseases like hyperprolactinemia and Parkinson's disease. Moreover, l-DOPA, produced in monoenzymatic TH neurons, is assumed to play a role of a neurotransmitter or neuromodulator affecting the target neurons via catecholamine receptors. Thus, numerous widespread neurons expressing individual complementary enzymes of DA synthesis serve to produce DA in cooperation that is a compensatory reaction at failure of DA-ergic neurons.
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Affiliation(s)
- Michael V Ugrumov
- Institute of Developmental Biology and Centre for Brain Research, Russian Academy of Sciences, Moscow, Russia; Institute of Normal Physiology RAMS, Moscow, Russia.
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Melnikova VI, Lyupina YV, Lavrentieva AV, Sapronova AY, Ugrumov MV. Synthesis of dopamine in non-dopaminergic neurons of the mediobasal hypothalamus of adult rats. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2012; 446:286-9. [PMID: 23129274 DOI: 10.1134/s0012496612050122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Indexed: 11/22/2022]
Affiliation(s)
- V I Melnikova
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
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Calas A. [Endocrine neurons and neurotransmission: 40 years of cytochemical studies]. ANNALES PHARMACEUTIQUES FRANÇAISES 2010; 68:27-35. [PMID: 20176160 DOI: 10.1016/j.pharma.2009.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 11/20/2009] [Accepted: 11/24/2009] [Indexed: 11/25/2022]
Abstract
Conceptual advances about chemical neurotransmission during the last 40 years have benefited a lot from histocytochemical approaches and from a particular experimental model, the endocrine hypothalamic neurons. New concepts like cotransmission, neuronal versatility, somatodendritic release of neurotransmitters, volume transmission, differential routing or cooperative synthesis of mediators, have often been issued from this set of methodologies and from their application to neurosecretory neurons. This review, mainly based on the results of our group, is aiming at illustrating how the peculiar metabolism of these neurons and their location at the neuro-endocrine interface have allowed discovering new aspects of neurotransmission, first considered as exceptions but then generalized to the whole nervous system. These new concepts shed lights on the normal functioning of the brain and definitely contribute to diversify pharmacological approaches of pathological neurotransmission.
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Affiliation(s)
- A Calas
- Inserm U 862, neurocentre Magendie, 33077 Bordeaux cedex, France.
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Developing Brain as an Endocrine Organ: A Paradoxical Reality. Neurochem Res 2010; 35:837-50. [DOI: 10.1007/s11064-010-0127-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2010] [Indexed: 01/09/2023]
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Non-dopaminergic neurons partly expressing dopaminergic phenotype: distribution in the brain, development and functional significance. J Chem Neuroanat 2009; 38:241-56. [PMID: 19698780 DOI: 10.1016/j.jchemneu.2009.08.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Revised: 08/06/2009] [Accepted: 08/12/2009] [Indexed: 11/23/2022]
Abstract
Besides the dopaminergic (DA-ergic) neurons possessing the whole set of enzymes of DA synthesis from l-tyrosine and the DA membrane transporter (DAT), the neurons partly expressing the DA-ergic phenotype have been first discovered two decades ago. Most of the neurons express individual enzymes of DA synthesis, tyrosine hydroxylase (TH) or aromatic l-amino acid decarboxylase (AADC) and lack the DAT. A list of the neurons partly expressing the DA-ergic phenotype is not restricted to so-called monoenzymatic neurons, e.g. it includes some neurons co-expressing both enzymes of DA synthesis but lacking the DAT. In contrast to true DA-ergic neurons, monoenzymatic neurons and bienzymatic non-dopaminergic neurons lack the vesicular monoamine transporter 2 (VMAT2) that raises a question about the mechanisms of storing and release of their final synthetic products. Monoenzymatic neurons are widely distributed all through the brain in adulthood being in some brain regions even more numerous than DA-ergic neurons. Individual enzymes of DA synthesis are expressed in these neurons continuously or transiently in norm or under certain physiological conditions. Monoenzymatic neurons, particularly those expressing TH, appear to be even more numerous and more widely distributed in the brain during ontogenesis than in adulthood. Most populations of monoenzymatic TH neurons decrease in number or even disappear by puberty. Functional significance of monoenzymatic neurons remained uncertain for a long time after their discovery. Nevertheless, it has been shown that most monoenzymatic TH neurons and AADC neurons are capable to produce l-3,4-dihydroxyphenylalanine (L-DOPA) from l-tyrosine and DA from L-DOPA, respectively. L-DOPA produced in monoenzymatic TH neurons is assumed to play a role of a neurotransmitter or neuromodulator acting on target neurons via catecholamine receptors. Moreover, according to our hypothesis L-DOPA released from monoenzymatic TH neurons is captured by monoenzymatic AADC neurons for DA synthesis. Such cooperative synthesis of DA is considered as a compensatory reaction under a failure of DA-ergic neurons, e.g. in neurodegenerative diseases like hyperprolactinemia and Parkinson's disease.Thus, a substantial number of the brain neurons express partly the DA-ergic phenotype, mostly individual complementary enzymes of DA synthesis, serving to produce DA in cooperation that is supposed to be a compensatory reaction under the failure of DA-ergic neurons.
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Abstract
Juvenile social play behaviour is one of the earliest forms of non-mother directed social behaviour in rodents. Juvenile social play behaviour is sexually dimorphic, with males exhibiting higher levels compared to females, making it a useful model to study both social development and sexual differentiation of the brain. As with most sexually dimorphic behaviour, juvenile play behaviour is organised by neonatal steroid hormone exposure. The developmental organisation of juvenile play behaviour also appears to be influenced by the early maternal environment. This review will focus briefly on why and how rats play, some brain regions controlling play behaviour, and how neurotransmitters and the social environment converge within the developing brain to influence sexual differentiation of juvenile play behaviour.
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Affiliation(s)
- A P Auger
- Psychology Department, University of Wisconsin, Madison, WI 53706, USA.
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Ugrumov MV. [Synthesis of monoamines by non-monoaminergic neurons: illusion or reality?]. ACTA ACUST UNITED AC 2009; 203:75-85. [PMID: 19358813 DOI: 10.1051/jbio:2009013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In contrast to monoaminergic (MA-ergic) neurons possessing the whole set of the enzymes for MA synthesis from the precursor amino-acid, some, mostly peptidergic, neurons co-express only one of the enzymes of monoamine synthesis. They are widely distributed in the brain, being particularly numerous in ontogenesis and, in adulthood, under certain physiological conditions. Most monoenzymatic neurons possess one of the enzymes for dopamine (DA) synthesis, tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC). TH and AADC are enzymatically active in a substantial number of monoenzymatic neurons, where they are capable of converting L-tyrosine to L-3,4-dihydroxy-phenylalanine (L-DOPA) and L-DOPA to dopamine (DA) (or 5-hydroxy-tryptophan, 5-HTP to serotonin), respectively. According to our data L-DOPA synthesized in monoenzymatic TH-neurons is released and taken up by monoenzymatic AADC-neurons for DA synthesis. Moreover, L-DOPA captured by dopaminergic neurons and serotoninergic neurons serves to stimulate dopamine synthesis in the former and to start DA synthesis in the latter. Cooperative synthesis of MAs is considered as a compensatory reaction under a failure of MA-ergic neurons, e.g. in neurodegenerative diseases like hyperprolactinemia and Parkinson's disease, which are developed primarily because of degeneration of DA-ergic neurons of the tuberoinfundibular system and the nigrostriatal system, respectively. Noteworthy, the neurotoxin-induced increase of prolactin secretion returns with time to a normal level due to the stimulation of DA synthesis by the tuberoinfundibular most probably monoenzymatic neurons. The same compensatory mechanism is supposed to be used under the failure of the nigrostriatal DA-ergic system that is manifested by an increased number of monoenzymatic neurons in the striatum of animals with neurotoxin-induced parkinsonism and in humans with Parkinson's disease. Expression of the enzymes of MA synthesis in non-monoaminergic neurons is controlled by intercellular signals such as classical neurotransmitters (catecholamines), etc. Thus, a substantial number of brain neurons express partly the monoaminergic phenotype, namely individual complementary enzymes of MA synthesis, serving to produce MAs in cooperation, which is considered as a compensatory reaction under the failure of MA-ergic neurons.
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Affiliation(s)
- Mikhail V Ugrumov
- Institut de Biologie du Développement, Académie Russe des Sciences et Institut de Physiologie Normale, Académie Russe des Sciences Médicales, 26 rue Vavilov, 117808 Moscou, Russie.
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Imbesi R, Castrogiovanni P. Embryonic and postnatal development in experimental tryptophan deprived rats. A preliminary study. J Mol Histol 2008; 39:487-98. [DOI: 10.1007/s10735-008-9188-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 07/24/2008] [Indexed: 10/21/2022]
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Olesen KM, Auger CJ, Auger AP. Regulation of progestin receptor expression in the developing rat brain by a dopamine d1 receptor antagonist. J Neuroendocrinol 2007; 19:481-8. [PMID: 17561880 DOI: 10.1111/j.1365-2826.2007.01554.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Steroid receptors within the developing brain influence a variety of cellular processes that endure into adulthood, altering both behaviour and physiology. Therefore, it is important to understand how steroid receptor expression is regulated during early brain development. Most studies indicate that oestradiol, by acting upon oestrogen receptors, increases the expression of progestin receptors in the developing brain. We have recently observed an additional mechanism by which dopamine can increase the expression of progestin receptors in developing female rat brain. That is, we found that a dopamine D1 receptor agonist can further increase progestin receptor expression by activating oestrogen receptors in a ligand-independent manner within restricted areas of female brain; however, it is unclear whether dopamine D1 receptors are involved in the normally occurring expression of progestin receptors in developing male and female brain. To investigate this, we examined whether a dopamine D1 receptor antagonist can disrupt the normal developmental expression of progestin receptors in both male and female rat brain. We report that treatment with a dopamine D1 receptor antagonist reduces progestin receptor expression within some, but not all, regions of the developing rat brain in a sex-specific manner. Some of the current findings also suggest that dopamine might be acting to prevent sex differences in progestin receptor expression in some areas while contributing to a sex difference in other areas.
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Affiliation(s)
- K M Olesen
- Department of Psychology, University of Wisconsin, Madison, WI 53706, USA
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Sardinha FLC, Telles MM, Albuquerque KT, Oyama LM, Guimarães PAMP, Santos OFP, Ribeiro EB. Gender difference in the effect of intrauterine malnutrition on the central anorexigenic action of insulin in adult rats. Nutrition 2006; 22:1152-61. [PMID: 17029904 DOI: 10.1016/j.nut.2006.07.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 07/05/2006] [Accepted: 07/09/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE We evaluated whether insulin hypophagia and hypothalamic signaling are affected in adult rats exposed to intrauterine undernutrition. METHODS Pregnant rats ate ad libitum throughout pregnancy and lactation (control, C) or 50% of control intake in the first 2 wk of pregnancy (restricted, R). Four-month-old C and R progeny received insulin or vehicle intracerebroventricular injections for evaluation of 24-h food intake, hypothalamic insulin receptor (IR), and IR substrate-1 (IRS-1) protein content and tyrosine phosphorylation, pp185 phosphorylation, and IRS-1 association with phosphatidylinositol 3-kinase (PI3-K). RESULTS With respect to males, R males had normal body composition and insulin-induced hypophagia. IR protein levels were lower but IR phosphorylation was higher in R than in C males. IRS-1 levels and phosphorylation were similar between C and R males, insulin stimulated an IRS-1/PI3-K association in C but not in R males, and pp185 phosphorylation was higher in R than in C males. For females, body fat and serum leptin were elevated in R females. Insulin inhibited food intake in C but not in R females. Insulin-induced IR phosphorylation and protein levels of IR and IRS-1 were higher in R than in C females. However, IRS-1 and pp185 phosphorylation and IRS-1/PI3-K association were significantly stimulated by insulin in C but not in R females. CONCLUSIONS Female adult rats exposed to intrauterine undernutrition had increased adiposity, marked impairment of hypothalamic insulin signaling, and loss of insulin-induced hypophagia. These disturbances were less severe or even absent in male progeny. The findings show that female progeny are more susceptible than their male siblings to the effects of maternal malnutrition.
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Affiliation(s)
- Fátima L C Sardinha
- Department of Physiology, Division of Nutrition Physiology, Federal University of São Paulo-UNIFESP, São Paulo, Brazil
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Mel'nikova VI, Lavrent'eva AV, Kudrin VS, Raevskii KS, Ugryumov MV. Dopamine Synthesis by Non-Dopaminergic Neurons in the Arcuate Nucleus of Rat Fetuses. ACTA ACUST UNITED AC 2005; 35:809-13. [PMID: 16132261 DOI: 10.1007/s11055-005-0129-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Indexed: 10/25/2022]
Abstract
The aim of the present work was to verify the hypothesis that non-dopaminergic neurons expressing individual complementary dopamine synthesis enzymes can perform the co-located synthesis of dopamine. According to this hypothesis, neurons expressing tyrosine hydroxylase use L-tyrosine for the synthesis of L-dihydroxyphenylalanine (L-DOPA), which then enters neurons expressing aromatic amino acid decarboxylase, which converts L-DOPA to dopamine. Experiments were performed using the mediobasal hypothalamus of rat fetuses, which mostly contains single-enzyme neurons (>99%) and occasional double-enzyme neurons (<1%). Controls were obtained from the fetal substantia nigra, which is enriched with dopaminergic neurons. High-performance liquid chromatography was used to measure levels of dopamine and L-DOPA in cell extracts and the incubation medium after incubation in the presence and absence of exogenous L-tyrosine. Addition of L-tyrosine to the medium led to increases in the level of synthesis and release of L-DOPA in the mediobasal hypothalamus and substantia nigra. In addition, L-tyrosine increased dopamine synthesis in the substantia nigra and decreased dopamine synthesis in the mediobasal hypothalamus. This regional difference in levels of dopamine synthesis is probably due to inhibition of the uptake of L-DOPA from the intercellular medium by neurons in the mediobasal hypothalamus containing aromatic amino acid decarboxylase, due to the competitive binding of the L-DOPA transporter by L-tyrosine. Thus, these results provide the first evidence for the co-located synthesis of dopamine by non-dopaminergic neurons expressing single complementary enzymes involved in the synthesis of this neurotransmitter.
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Affiliation(s)
- V I Mel'nikova
- N. K. Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, 119334, Moscow, Russia
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Ershov PV, Ugrumov MV, Calas A, Krieger M, Thibault J. Degeneration of dopaminergic neurons triggers an expression of individual enzymes of dopamine synthesis in non-dopaminergic neurons of the arcuate nucleus in adult rats. J Chem Neuroanat 2005; 30:27-33. [PMID: 15935614 DOI: 10.1016/j.jchemneu.2005.04.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Revised: 01/21/2005] [Accepted: 04/04/2005] [Indexed: 11/24/2022]
Abstract
Non-dopaminergic neurons expressing individual complementary enzymes dopamine (DA) synthesis were shown to produce DA in cooperation [Ugrumov, M., Melnikova, V., Ershov, P., Balan, I., Calas A., 2002. Tyrosine hydroxylase- and/or aromatic L-amino acid decarboxylase-expressing neurons in the rat arcuate nucleus: ontogenesis and functional significance. Psychoneuroendocrinology 27, 533-548; Ugrumov, M.V., Melnikova, V.I., Lavrentyeva, A.V., Kudrin, V.S., Rayevsky, K.S., 2004. Dopamine synthesis by non-dopaminergic neurons expressing individual complementary enzymes of the dopamine synthetic pathway in the arcuate nucleus of fetal rats. Neuroscience 124, 629-635]. This study was aimed at testing our hypothesis that the cooperative synthesis of DA in non-dopaminergic neurons is an adaptive reaction under functional insufficiency of the dopaminergic system. Functional insufficiency of the tuberoinfundibular dopaminergic system was provoked by 6-OHDA-induced degeneration of dopaminergic neurons in the arcuate nucleus in adult rats. Bienzymatic (dopaminergic) neurons and monoenzymatic neurons expressing tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC) were detected with a double-immunofluorescent technique on cryostat sections. The 6-OHDA-induced degeneration of dopaminergic neurons was accompanied by a significant increase of the number of monoenzymatic TH neurons and AADC neurons that appears to support our hypothesis. The reaction of bienzymatic and monoenzymatic neuron populations to the 6-OHDA administration occurred to be region-specific. The former disappeared in the dorsomedial region of the arcuate nucleus while the latter increased in the ventrolateral region. Thus, degeneration of dopaminergic neurons in the arcuate nucleus of adult rats is accompanied by the expression of individual enzymes of DA synthesis in non-dopaminergic neurons that may be an adaptive reaction.
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Affiliation(s)
- P V Ershov
- Laboratory of Neurohistology, Institute of Normal Physiology, Russian Academy of Medical Sciences, 8 Baltiiskaya St., Moscow, Russia
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Ugrumov MV. Developing Brain as a Giant Multipotent Endocrine Gland. NEUROPHYSIOLOGY+ 2005. [DOI: 10.1007/s11062-005-0069-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ugrumov MV, Melnikova VI, Lavrentyeva AV, Kudrin VS, Rayevsky KS. Dopamine synthesis by non-dopaminergic neurons expressing individual complementary enzymes of the dopamine synthetic pathway in the arcuate nucleus of fetal rats. Neuroscience 2004; 124:629-35. [PMID: 14980733 DOI: 10.1016/j.neuroscience.2004.01.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2004] [Indexed: 11/29/2022]
Abstract
This study was aimed to test our hypothesis about dopamine (DA) synthesis by non-DAergic neurons expressing individual complementary enzymes of the DA synthetic pathway in cooperation, i.e. L-dihydroxyphenylalanine (L-DOPA) synthesized in tyrosine hydroxylase (TH)-expressing neurons is transported to aromatic L-amino acid decarboxylase (AADC)-expressing neurons for conversion to DA. The mediobasal hypothalamus of rats at the 21st embryonic day was used as an experimental model because it contains mainly monoenzymatic TH neurons and AADC neurons (>99%) whereas the fraction of bienzymatic (DAergic) neurons does not exceed 1%. The fetal substantia nigra containing DAergic neurons served as a control. DA and L-DOPA were measured by high performance liquid chromatography in: (1) cell extracts of the cell suspension prepared ex tempora; (2) cell extracts and incubation medium after the static incubation of the cell suspension with, or without exogenous L-tyrosine; (3) effluents of the incubation medium during perifusion of the cell suspension in the presence, or the absence of L-tyrosine. Total amounts of DA and L-DOPA in the incubation medium and cell extracts after the static incubation were considered as the indexes of the rates of their syntheses. L-Tyrosine administration caused the increased L-DOPA synthesis in the mediobasal hypothalamus and substantia nigra. Moreover, L-tyrosine provoked an increase of DA synthesis in the substantia nigra and its decrease in the mediobasal hypothalamus. This contradiction is most probably explained by the L-tyrosine-induced competitive inhibition of the L-DOPA transport to the monoenzymatic AADC-neurons after its release from the monoenzymatic TH neurons. Thus, this study provides convincing evidence of cooperative DA synthesis by non-DAergic neurons expressing TH or AADC in fetal rats at the end of the intrauterine development.
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Affiliation(s)
- M V Ugrumov
- Laboratory of Hormonal Regulations, Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilov Street, Moscow 117334, Russia.
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Ershov PV, Ugrumov MV, Calas A, Makarenko IG, Krieger M, Thibault J. Neurons possessing enzymes of dopamine synthesis in the mediobasal hypothalamus of rats. Topographic relations and axonal projections to the median eminence in ontogenesis. J Chem Neuroanat 2002; 24:95-107. [PMID: 12191726 DOI: 10.1016/s0891-0618(02)00019-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We evaluated the topographic relations between tyrosine hydroxylase (TH)- and/or aromatic L-amino acid decarboxylase (AADC)-immunoreactive neurons in the arcuate nucleus (AN), as well as between TH- and/or AADC-immunoreactive axons in the median eminence (ME) in rats at the 21st embryonic day, 9th postnatal day, and in adulthood. The double-immunofluorescent technique in combination with confocal microscopy was used. Occasional bienzymatic neurons but numerous monoenzymatic TH- or AADC-immunoreactive neurons were observed in fetuses. There was almost no overlap in the distribution of monoenzymatic neurons, and therefore few appositions were observed in between. In postnatal animals, numerous bienzymatic neurons appeared in addition to monoenzymatic neurons. They were distributed throughout the AN resulting in the increased frequency of appositions. Furthermore, specialized-like contacts between monoenzymatic TH- and AADC-immunoreactive neurons appeared. The quantification of the fibers in the ME showed that there were large specific areas of the monoenzymatic TH-immunoreactive fibers and bienzymatic fibers in fetuses, followed by the gradual reduction of the former and the increase of the latter to adulthood. The specific area of the monoenzymatic AADC-immunoreactive fibers in fetuses was rather low, and thereafter increased progressively to adulthood. The fibers of all the types were in apposition in the ME at each studied age. Close topographic relations between the neurons containing individual complementary enzymes of dopamine synthesis at the level of cell bodies and axons suggest functional interaction in between.
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Affiliation(s)
- Petr V Ershov
- Laboratory of Neurohistology, Institute of Normal Physiology, Russian Academy of Medical Sciences, 8 Baltiiskaya St., Moscow, Russia
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Ugrumov M, Melnikova V, Ershov P, Balan I, Calas A. Tyrosine hydroxylase- and/or aromatic L-amino acid decarboxylase-expressing neurons in the rat arcuate nucleus: ontogenesis and functional significance. Psychoneuroendocrinology 2002; 27:533-48. [PMID: 11965353 DOI: 10.1016/s0306-4530(01)00091-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This study has evaluated in vivo, ex vivo and in vitro the ontogenesis and functional significance of the neurons of the arcuate nucleus (AN) expressing either individual enzymes of dopamine (DA) synthesis, tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC) as well as both of them in rats from the 17th embryonic day (E) till adulthood. Immunocytochemistry, image analysis, confocal microscopy, high performance liquid chromatography with electrochemical detection and radioimmunoassay were used to solve this problem. Monoenzymatic TH-containing neurons were initially observed on E18 located in the ventrolateral AN whereas the neurons expressing only AADC or both AADC and TH first appeared on E20 in the dorsomedial AN. On E21, the monoenzymatic TH- or AADC-expressing neurons comprised more than 99% of the whole neuron population expressing the DA-synthesizing enzymes. In spite of an extremely small number (<1%) of the neurons expressing both enzymes (DArgic neurons), the dissected AN (ex vivo) and its primary cell culture (in vitro) contained a surprisingly high amount of DA and L-dihydroxyphenylalanine (L-DOPA) which were released in response to membrane depolarization. Furthermore, DA production in the AN of fetuses occurred to be sufficient to provide an inhibitory control of prolactin secretion, as in adults. The above data suggest that DA could be synthesized, at least in the AN of fetuses, by monoenzymatic neurons containing either TH or AADC, in co-operation. This hypothesis may be extended to adult animals as their AN contained the same populations of the neurons expressing DA-synthesizing enzymes as in fetuses though the proportion of true DArgic neurons increased up to 38%. During ontogenesis, the monoenzymatic TH- and AADC-containing neurons established axosomatic and axo-axonal junctions that might facilitate the L-DOPA transport from the former to the latter. Moreover, the monoenzymatic AADC-expressing neurons project their axons to the median eminence, thereby, providing the pathway for the DA transport toward the hypophysial portal circulation. Thus, DA appears to be synthesized in the AN not only by DArgic neurons but also by monoenzymatic TH- and AADC-expressing neurons in co-operation.
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Affiliation(s)
- M Ugrumov
- Laboratory of Hormonal Regulations, Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 26 Vavilov St., Moscow 117808, Russia.
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Ugryumov MV, Mel'nikova VI, Ershov PV, Balan IS, Kalas A. Non-dopaminergic neurons expressing dopamine synthesis enzymes: differentiation and functional significance. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2002; 32:299-307. [PMID: 12135344 DOI: 10.1023/a:1015018508998] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The development and functional significance of neurons in the arcuate nucleus expressing tyrosine hydroxylase and/or aromatic L-amino acid decarboxylase were studied in rat fetuses, neonates, and adults using immunocytochemical (single and double immunolabeling of tyrosine hydroxylase and aromatic L-amino acid decarboxylase) methods with a confocal microscope and computerized image analysis, HPLC with electrochemical detection, and radioimmunological analysis. Single-enzyme neurons containing tyrosine hydroxylase were first seen on day 18 of embryonic development in the ventrolateral part of the arcuate nucleus. Neurons expressing only aromatic L-amino acid decarboxylase or both enzymes of the dopamine synthesis pathway were first seen on day 20 of embryonic development, in the dorsomedial part of the nucleus. On days 20-21 of embryonic development, dopaminergic (containing both enzymes) neurons amounted to less than 1% of all neurons expressing tyrosine hydroxylase and/or aromatic L-amino acid decarboxylase. Nonetheless, in the ex vivo arcuate nucleus and in primary neuron cultures from this structure, there were relatively high leveLs of dopamine and L-dihydroxyphenylalanine (L-DOPA), and these substances were secreted spontaneously and in response to stimulation. In addition. dopamine levels in the arcuate nucleus in fetuses were sufficient to support the inhibitory regulation of prolactin secretion by the hypophysis, which is typical of adult animals. During development, the proportion of dopaminergic neurons increased, reaching 38% in adult rats. Specialized contacts between single-enzyme tyrosine hydroxylase-containing and aromatic L-amino acid decarboxylase-containing neurons were present by day 21 of embryonic development; these were probably involved in transporting L-DOPA from the former neurons to the latter. It was also demonstrated that the axons of single-enzyme decarboxylase-containing neurons projected into the median eminence, supporting the secretion of dopamine into the hypophyseal portal circulation. Thus, dopamine is probably synthesized in the arcuate nucleus not only by dopaminergic neurons, but also by neurons expressing only tyrosine hydroxylase or aromatic L-amino acid decarboxylase.
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Affiliation(s)
- M V Ugryumov
- Laboratory of Hormonal Regulation, N. K. Kol'tsov Institute of Developmental Biology, Moscow, Russia
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Ershov PV, Ugrumov MV, Calas A, Krieger M, Thibault J. Differentiation of tyrosine hydroxylase-synthesizing and/or aromatic L-amino acid decarboxylase-synthesizing neurons in the rat mediobasal hypothalamus: quantitative double-immunofluorescence study. J Comp Neurol 2002; 446:114-22. [PMID: 11932930 DOI: 10.1002/cne.10173] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this double-immunofluorescence study, we first quantified the neurons of the arcuate nucleus as immunoreactive (+) for tyrosine hydroxylase (TH) and/or aromatic L-amino acid decarboxylase (AADC) in rats at embryonic day 21 (E21), at postnatal day 9 (P9), and in adulthood by using conventional fluorescent or confocal microscopy. On E21, monoenzymatic (TH(+)AADC immunonegative (-) and TH(-)AADC(+)) neurons and bienzymatic (TH(+)AADC(+)) neurons accounted for 99% and 1%, respectively, of the whole neuron population expressing enzymes of dopamine synthesis. Further development was characterized by the dramatic increase in TH(+)AADC(-) dorsomedial and TH(+)AADC(+) dorsomedial populations from E21 to P9 as well as by the increase in the TH(+)AADC(+) dorsomedial population (in females) and a drop in the TH(+)AADC(-) ventrolateral and TH(+)AADC(-) dorsomedial (in males) populations from P9 to adulthood. In contrast to TH(+)AADC(-) (in males) and TH(+)AADC(+) neurons, the TH(-)AADC(+) neurons did not change in number from E21 to adulthood. Thus, in rat fetuses, the neurons synthesizing TH and/or AADC were mainly monoenzymatic, whereas during postnatal life the fraction of bienzymatic neurons increased by up to 60%.
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Affiliation(s)
- Petr V Ershov
- Laboratory of Neurohistology, Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow 125315, Russia
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Abstract
Dopamine is a small and relatively simple molecule that fulfills diverse functions. Within the brain, it acts as a classical neurotransmitter whose attenuation or overactivity can result in disorders such as Parkinson's disease and schizophrenia. Major advances in the cloning and characterization of biosynthetic enzymes, transporters, and receptors have increased our knowledge regarding the metabolism, release, reuptake, and mechanism of action of dopamine. Dopamine reaches the pituitary via hypophysial portal blood from several hypothalamic nerve tracts that are regulated by PRL itself, estrogens, and several neuropeptides and neurotransmitters. Dopamine binds to type-2 dopamine receptors that are functionally linked to membrane channels and G proteins and suppresses the high intrinsic secretory activity of the pituitary lactotrophs. In addition to inhibiting PRL release by controlling calcium fluxes, dopamine activates several interacting intracellular signaling pathways and suppresses PRL gene expression and lactotroph proliferation. Thus, PRL homeostasis should be viewed in the context of a fine balance between the action of dopamine as an inhibitor and the many hypothalamic, systemic, and local factors acting as stimulators, none of which has yet emerged as a primary PRL releasing factor. The generation of transgenic animals with overexpressed or mutated genes expanded our understanding of dopamine-PRL interactions and the physiological consequences of their perturbations. PRL release in humans, which differs in many respects from that in laboratory animals, is affected by several drugs used in clinical practice. Hyperprolactinemia is a major neuroendocrine-related cause of reproductive disturbances in both men and women. The treatment of hyperprolactinemia has greatly benefited from the generation of progressively more effective and selective dopaminergic drugs.
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Affiliation(s)
- N Ben-Jonathan
- Department of Cell Biology, Neurobiology, and Anatomy, University of Cincinnati Medical Center, Cincinnati, Ohio 45267, USA.
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Balan IS, Ugrumov MV, Calas A, Mailly P, Krieger M, Thibault J. Tyrosine hydroxylase-expressing and/or aromatic L-amino acid decarboxylase-expressing neurons in the mediobasal hypothalamus of perinatal rats: differentiation and sexual dimorphism. J Comp Neurol 2000; 425:167-76. [PMID: 10954837 DOI: 10.1002/1096-9861(20000918)425:2<167::aid-cne1>3.0.co;2-k] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this quantitative and semiquantitative immunocytochemical study, the authors evaluated the differentiation of neurons expressing tyrosine hydroxylase (TH) and/or aromatic L-amino acid decarboxylase (AADC) in the mediobasal hypothalamus (MBH) of male and female rats on embryonic day 18 (E18), E20, and postnatal day 9 (P9). Four neuronal populations were distinguished according to either enzyme expression or neuron location. The earliest and most prominent first population was represented by TH-immunoreactive (IR)/AADC-immunonegative (IN) neurons that were detected initially at E18 and always were located in the ventrolateral region of the MBH. The second population of TH-IN/AADC-IR neurons was observed first at E20 and, after that time, was distributed dorsomedially. The third minor population of TH-IR/AADC-IR neurons initially was detected at E20 and was located dorsomedially. The fourth population was represented by TH-IR/AADC-IN neurons that were distributed in the dorsomedial region at any studied age. The numbers of TH-IR and AADC-IR neurons increased from their initial detection at E18 and E20 until P9. The area of TH-IR and AADC-IR neurons also increased from E18 to E20 and from E20 to P9, respectively. Both TH-IR and AADC-IR neurons showed sex differences in the neuron number, size, and optic density (OD). The numbers of TH-IR neurons in males exceeded those of females at E20 and at P9, although, at P9, sexual dimorphism was a characteristic only of the ventrolateral population. The area and OD of TH-IR neurons from females exceeded those from males in the entire mediobasal hypothalamus (MBH) at E18 and E20 but only in its dorsomedial region at P9. Sexual dimorphism also was an attribute of AADC-IR neurons at E20 and P9. Their number, size, and OD were significantly higher in females than in males. Thus, the MBH of perinatal rats contained two major populations of TH-IR/AADC-IN or TH-IN-AADC-IR neurons and a minor population of TH-IR/AADC-IR neurons. The differentiating neurons expressing either enzyme showed sexual dimorphism.
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Affiliation(s)
- I S Balan
- Laboratory of Neurohistology, Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow 117808, Russia
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