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Iwanaga T, Hozumi Y, Takahashi-Iwanaga H. Immunohistochemical demonstration of dopamine receptor D2R in the primary cilia of the mouse pituitary gland. ACTA ACUST UNITED AC 2011; 32:225-35. [PMID: 21673453 DOI: 10.2220/biomedres.32.225] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dopamine regulates the synthesis and secretion of prolactin and α-MSH/β-endorphin in lactotrophs and melanotrophs, respectively. While a predominant dopamine receptor, D2R, is known to be expressed in both the anterior and intermediate lobes of the pituitary gland, no previous immunohistochemical studies have shown the existence of D2R in the plasma membrane of pituitary endocrine cells. The present study clearly demonstrated a selective localization of the D2R immunoreactivity in primary cilia of lactotrophs and melanotrophs in the mouse adenohypophysis. Another immunoreactivity of D2R was found along the plasma membrane of melanotrophs. The intensity of immunoreactivity for D2R in the primary cilia of lactrotrophs changed during the estrous cycle and with genital conditions in contrast to a consistent immunolabeling in the melanotrophs. Since there is accumulating evidence that the primary cilium functions as a sensory device at a cellular level, the D2R-expressing primary cilia in the pituitary gland may be involved in the sensation of dopamine and dopaminergic compounds-though their involvement differs between the anterior and intermediate lobes.
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Affiliation(s)
- Toshihiko Iwanaga
- Laboratory of Histology and Cytology, Hokkaido University Graduate School of Medicine, Sapporo.
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Christensen HR, Zeng Q, Murawsky MK, Gregerson KA. Estrogen regulation of the dopamine-activated GIRK channel in pituitary lactotrophs: implications for regulation of prolactin release during the estrous cycle. Am J Physiol Regul Integr Comp Physiol 2011; 301:R746-56. [PMID: 21653876 DOI: 10.1152/ajpregu.00138.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prolactin (PRL), synthesized and secreted from lactotrophs of the anterior pituitary gland, is tonically inhibited by hypothalamic dopamine (DA) throughout the female reproductive (estrous) cycle. Our laboratory has shown that DA hyperpolarizes these cells by activating G protein-coupled inwardly rectifying K(+) (GIRK) channels; however, this response is only observed on proestrus. While the cellular mechanisms that allow for functional expression of this unique DA-signaling pathway are unclear, we hypothesized that activation of the DA-GIRK effector pathway is due to the rise in circulating estrogen (E₂) during the preceding day of diestrus. Thus, we examined the effects of E₂ on primary lactotrophs isolated from female rats. Treatment with a physiological concentration of E₂ (40-80 pg/ml, in vivo or in vitro) induced a proestrous phenotype in diestrous lactotrophs. These cells exhibited a DA-induced membrane hyperpolarization, as well as a secretory rebound of PRL following DA withdrawal (characteristic of proestrous cells). Internal dialysis of GTPγS demonstrated that E₂ exposure enabled functional expression of GIRK channels, and this regulation by E₂ did not involve the D₂R. The effect of E₂ was blocked by the receptor antagonist, ICI 182,780, and by the protein synthesis inhibitor, cycloheximide. Single-cell analysis revealed increased mRNA expression of GIRK channel subunits in E₂-treated lactotrophs. While E₂ is known to have multiple actions on the lactotroph, the present findings illuminate a novel action of E₂ in lactotrophs-regulation of the expression of a DA effector, the GIRK channel.
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Affiliation(s)
- Heather R Christensen
- James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, USA.
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Liu B, Arbogast LA. Progesterone decreases tyrosine hydroxylase phosphorylation state and increases protein phosphatase 2A activity in the stalk-median eminence on proestrous afternoon. J Endocrinol 2010; 204:209-19. [PMID: 19945993 PMCID: PMC2808445 DOI: 10.1677/joe-09-0335] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The progesterone (P(4)) rise on proestrous afternoon is associated with dephosphorylation of tyrosine hydroxylase (TH) and reduced TH activity in the stalk-median eminence (SME), which contributes to the proestrous prolactin surge in rats. In the present study, we investigated the time course for P(4) effect on TH activity and phosphorylation state, as well as cAMP levels and protein phosphatase 2A (PP2A) activity and quantity, in the SME on proestrous morning and afternoon. P(4) (7.5 mg/kg, s.c.) treatment on proestrous afternoon decreased TH activity and TH phosphorylation state at Ser-31 and Ser-40 within 1 h, whereas morning administration of P(4) had no 1 h effect on TH. PP2A activity in the SME was enhanced after P(4) treatment for 1 h on proestrous afternoon without a change in PP2A catalytic subunit quantity, whereas P(4) treatment had no effect on PP2A activity or quantity on proestrous morning. cAMP levels in the SME were unchanged with 1 h P(4) treatment. At 5 h after P(4) treatment, TH activity and phosphorylation state declined coincident with an increase in plasma prolactin in both P(4)-treated morning and afternoon groups. PP2A activity in the SME was unchanged in 5 h P(4)-treated rat. Our data suggest that P(4) action on tuberoinfundibular dopaminergic (TIDA) neurons involves at least two components. A more rapid (1 h) P(4) effect engaged only on proestrous afternoon likely involves the activation of PP2A. The longer P(4) action on TIDA neurons is evident on both the morning and afternoon of proestrus and may involve a common, as yet unidentified, mechanism.
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Affiliation(s)
- Bin Liu
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-6523, USA
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Dufour S, Sebert ME, Weltzien FA, Rousseau K, Pasqualini C. Neuroendocrine control by dopamine of teleost reproduction. JOURNAL OF FISH BIOLOGY 2010; 76:129-160. [PMID: 20738703 DOI: 10.1111/j.1095-8649.2009.02499.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
While gonadotropin-releasing hormone (GnRH) is considered as the major hypothalamic factor controlling pituitary gonadotrophins in mammals and most other vertebrates, its stimulatory actions may be opposed by the potent inhibitory actions of dopamine (DA) in teleosts. This dual neuroendocrine control of reproduction by GnRH and DA has been demonstrated in various, but not all, adult teleosts, where DA participates in an inhibitory role in the neuroendocrine regulation of the last steps of gametogenesis (final oocyte maturation and ovulation in females and spermiation in males). This has major implications for inducing spawning in aquaculture. In addition, DA may also play an inhibitory role during the early steps of gametogenesis in some teleost species, and thus interact with GnRH in the control of puberty. Various neuroanatomical investigations have shown that DA neurones responsible for the inhibitory control of reproduction originate in a specific nucleus of the preoptic area (NPOav) and project directly to the region of the pituitary where gonadotrophic cells are located. Pharmacological studies showed that the inhibitory effects of DA on pituitary gonadotrophin production are mediated by DA-D2 type receptors. DA-D2 receptors have now been sequenced in several teleosts, and the coexistence of several DA-D2 subtypes has been demonstrated in a few species. Hypophysiotropic DA activity varies with development and reproductive cycle and probably is controlled by environmental cues as well as endogenous signals. Sex steroids have been shown to regulate dopaminergic systems in several teleost species, affecting both DA synthesis and DA-D2 receptor expression. This demonstrates that sex steroid feedbacks target DA hypophysiotropic system, as well as the other components of the brain-pituitary gonadotrophic axis, GnRH and gonadotrophins. Recent studies have revealed that melatonin modulates the activity of DA systems in some teleosts, making the melatonin-DA pathway a prominent relay between environmental cues and control of reproduction. The recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various internal and environmental cues. The plasticity of the DA neuroendocrine role observed in teleosts may have contributed to their large diversity of reproductive cycles.
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Affiliation(s)
- S Dufour
- Muséum National d'Histoire Naturelle, UMR Biologie des Organismes et Ecosystèmes Aquatiques" MNHN-CNRS-IRD-UPMC, 7 rue Cuvier, CP 32, 75231 Paris Cedex 05, France.
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5
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Joubert-Bression D, Brandi AM, Birman P, Peillon F. Effect of oestradiol on dopamine receptors and protein kinase C activity in the rat pituitary: binding of oestradiol to pituitary membranes. CIBA FOUNDATION SYMPOSIUM 2007; 153:156-68; discussion 168-71. [PMID: 2292210 DOI: 10.1002/9780470513989.ch9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Oestradiol exerts an important modulatory influence on the release of prolactin which is accomplished partly through disruption of the inhibitory influence of dopamine. We have focused on the status of the anterior pituitary D2 dopamine receptor in female rats treated chronically with oestradiol or progesterone. A direct membrane effect of these steroids on the dopamine system was also investigated in vitro. Both steroids affected the status of the D2 receptor, oestradiol decreasing the number of sites in vitro and progesterone increasing it both in vitro and in vivo. The in vitro studies demonstrated that these steroids exert a direct membrane effect on the D2 receptor. These results correlated with an in vitro short-term physiological effect of oestradiol and progesterone on the dopaminergic inhibition of prolactin release, oestradiol decreasing it while progesterone had the opposite effect. Binding studies with [3H] oestradiol on pituitary membranes revealed a site for oestradiol of high affinity and low capacity, indicating that oestradiol's membrane effects could be mediated by a specific receptor. In vivo treatment with oestradiol also induces proliferation of prolactin-secreting cells (lactotrophs). We focused on the effect of oestradiol on protein kinase C activity, which is involved in both secretion and proliferation. In female rats treated with oestradiol total protein kinase C activity was increased by 74% (particulate 90%, soluble 71%) in comparison with controls. This effect was reversed by concomitant treatment with a dopamine agonist. Thus in the pituitary oestradiol and progesterone affect the characteristics of membrane components that are implicated in the physiological control of the cell. Whether these effects are post-transcriptional only or are also mediated through direct membrane mechanisms needs further investigation.
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Szawka RE, Anselmo-Franci JA. A secondary surge of prolactin on the estrus afternoon. Life Sci 2004; 75:911-22. [PMID: 15193951 DOI: 10.1016/j.lfs.2004.01.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Accepted: 01/07/2004] [Indexed: 10/26/2022]
Abstract
It has been described that throughout the estrous cycle of the rat, plasma prolactin (PRL) is basal except on proestrus afternoon when a preovulatory surge occurs. However, there have been controversies about PRL levels on the estrus day. Thus, the aim of this study was to evaluate the existence of a secondary surge of PRL on estrus afternoon and correlate it with plasma estradiol levels. The jugular vein of cycling rats was cannulated at 14:00 h on proestrus and a blood sample was withdrawn at 17:00 h for plasma LH measurement and determination of the preovulatory LH surge occurrence. In order to exclude the regular cycling rats that do not present the gonadotropins preovulatory surge and do not ovulate, only rats showing the LH surge on proestrus were considered in this study. Blood samples were collected hourly during estrus from midnight to 9:00 h (group 1) and from 10:00 to 18:00 h (group 2). In group 1, PRL showed a descending profile from midnight to 9:00 h, whereas the estradiol concentrations were constant. In group 2, a secondary surge of PRL was observed in 20 of 25 (80%) rats and plasma estradiol remained constant, but was higher in animals with the PRL surge. Thus the present data suggest the occurrence of a secondary surge of PRL in the afternoon of estrus that seems to be related to plasma estradiol levels of estrus day, which might exert only a permissive role in this surge generation.
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Affiliation(s)
- Raphael Escorsim Szawka
- Faculdade de Medicina de Ribeirão Preto, Departamento de Fisiologia, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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Ursic M, Bavdek SV, Zabavnik J. The number of cells expressing dopamine D2 receptor mRNA in rat brain caudate putamen is higher in oestrus. J Anat 2003; 202:453-61. [PMID: 12739622 PMCID: PMC1571098 DOI: 10.1046/j.1469-7580.2003.00180.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dopamine D2 receptors (D2-Rs) in the central nervous system are involved in the control of locomotion, cognition, emotion and neuroendocrine secretion. The intensity of cellular responses to specific stimuli is dependent on the concentration of dopamine or its agonist, and the availability, as well as the concentration, of all the other components of the signalling pathway in the cell, including the receptors. Many factors can influence the level of mRNA encoding the receptors. In order to study the changes in the level of expression of the D2-R mRNA in the brain of female rats at different stages of the oestrous cycle, we used a quantitative in situ hybridization technique. Four groups of animals were analysed: rats in prooestrus (POE), oestrus (OE), dioestrus 1 (DOE1) and dioestrus 2 (DOE2). A 35S-labelled riboprobe was transcribed in vitro from the 1.5-kb D2-R cDNA. The caudate putamen of the rats, which shows the highest level of expression of D2-R mRNA in the brain, was examined. The number of silver grains per cell, representing hybridization of riboprobe, and the number of cells expressing the D2-R mRNA, were counted with the computer-assisted image analysis system Lucia-M. Our results show that the expression of the D2-R mRNA in the lateral striatum varies during the oestrous cycle, with the highest expression measured during DOE2. The number of cells expressing the D2-R mRNA also changes during the different phases, with the highest number being detected in OE. This indicates that during OE more cells transcribe the D2-R mRNA. The results suggest that the variations in the concentration of the D2-R mRNA in the caudate putamen of the rat brain at different stages of the reproductive cycle are caused by the combination of variable expression of the mRNA per cell and different number of the cells that express the mRNA.
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Affiliation(s)
- Matjaz Ursic
- Institute of Anatomy, Histology and Embryology, Veterinary Faculty, Ljubljana, Slovenia
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Gregerson KA. Functional expression of the dopamine-activated K(+) current in lactotrophs during the estrous cycle in female rats: correlation with prolactin secretory responses. Endocrine 2003; 20:67-74. [PMID: 12668870 DOI: 10.1385/endo:20:1-2:67] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Accepted: 12/20/2002] [Indexed: 11/11/2022]
Abstract
It is well established that hypothalamic dopamine (DA) is the major physiologic regulator of prolactin (PRL) secretion, exerting a tonic inhibition throughout most of the estrous cycle. A dramatic drop in the amount of DA perfusing the anterior pituitary occurs in the afternoon of proestrus and is critical for the production of the surge of PRL that occurs at that time. In my laboratory, we have identified and characterized a DA-activated K(+) channel (K(DA)) in lactotrophs derived from proestrous rats that underlies DA-induced membrane hyperpolarization of lactotrophs. We have also demonstrated that this hyperpolarization plays a critical role in both the inhibition of PRL release from proestrous cells and the PRL secretory rebound that occurs following DA withdrawal. We now report that the ability of DA to activate the K(DA) channel and elicit hyperpolarization in primary lactotrophs changes dramatically during the estrous cycle. Lactotrophs isolated from cycling female rats were studied using whole-cell voltage clamp. DA (1 microM) elicited a robust membrane K(+) current in the majority of proestrous lactotrophs (86%; 24.0 +/- 2.9 pA). By contrast, DA activated a considerably smaller membrane current (3.3 pA) in very few lactotrophs isolated from rats on either diestrus or estrus (8 and 0%, respectively). Using a perifusion system to examine temporal patterns of PRL release, we found that following application and withdrawal of DA, proestrous cells produced a robust secretory rebound, but diestrous and estrous cells did not. However, DA inhibited PRL release to the same extent regardless the stage of the cycle from which the cells were derived. These data are consistent with the presence of multiple DA effectors in lactotrophs and demonstrate that their relative importance shifts dramatically with changes in the endocrine status of the animal. We propose that the DA-activated K(+) channel (K(DA)) is a critical effector governing the unique secretory profile of PRL observed in proestrous animals.
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Affiliation(s)
- Karen A Gregerson
- Department of Pharmacological and Physiological Science, Saint Louis University, School of Medicine, St Louis, MO 63104, USA.
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DeMaria JE, Livingstone JD, Freeman ME. Ovarian steroids influence the activity of neuroendocrine dopaminergic neurons. Brain Res 2000; 879:139-47. [PMID: 11011015 DOI: 10.1016/s0006-8993(00)02763-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The secretion of prolactin (PRL) from the anterior lobe (AL) of the pituitary gland is tonically inhibited by dopamine (DA) of hypothalamic origin. While ovarian steroids play a role in the regulation of the secretion of PRL, their effect on all three populations of hypothalamic neuroendocrine dopaminergic neurons is not fully understood. In this study we describe the effects of ovarian steroids on regulation of the release of DA from tuberoinfundibular dopaminergic (TIDA), tuberohypophyseal dopaminergic (THDA) and periventricular-hypophyseal dopaminergic (PHDA) neurons. Adult female rats were bilaterally ovariectomized (OVX) and, 10 days following ovariectomy (day 0), injected with corn oil (vehicle), estrogen, or estrogen plus progesterone (day 1). Animals were sacrificed every 2 h from 09.00 to 21.00 h by rapid decapitation. Trunk blood was collected and the concentration of PRL in serum was determined by radioimmunoassay. The median eminence (ME) and the AL, intermediate (IL) and neural (NL) lobes of the pituitary gland were dissected and the concentration of DA and DOPAC in each was measured by HPLC-EC. OVX rats presented small but significant increases in the secretion of PRL at 15.00 and 17.00 h. Replacement of estrogen or estrogen plus progesterone increased the basal concentration of PRL. Moreover, injection of estrogen only, or estrogen plus progesterone increased the concentration of PRL in serum at 15.00 h through 19.00 h, respectively, followed by a decrease to baseline thereafter. The turnover of DA in the ME and NL of OVX rats increased at 13.00 and returned to low levels. Turnover of DA in the IL of OVX rats increased in the morning by 11.00 h and remained elevated before decreasing by 17.00 h. The turnover of DA in the ME, IL and NL of OVX rats increased by 19.00 h. Injection of estrogen advanced the increase of TIDA activity by 2 h in the ME compared to OVX rats. Moreover, administration of estrogen suppressed the activity of THDA and PHDA neurons in the afternoon compared to OVX rats. In estrogen plus progesterone-treated rats, the activity of hypothalamic neuroendocrine dopaminergic neurons terminating in the ME, IL, and NL was inhibited prior to the increase in the secretion of PRL. The concentration of DA in the AL diminished prior to the estrogen-induced increase of PRL. Administration of progesterone, in concert with estrogen, delayed the increase of PRL in serum and the decrease of DA in the AL, compared to estrogen-treated rats, by 4 h. These data suggest a major role for ovarian steroids in controlling increases in the secretion of PRL by not only stimulating PRL release from lactotrophs, but also by inhibiting the activity of all three populations of hypothalamic neuroendocrine DAergic neurons.
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Affiliation(s)
- J E DeMaria
- Program in Neuroscience, Department of Biological Science, Florida State University, Tallahassee, FL 32306-4340, USA
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Freeman ME, Kanyicska B, Lerant A, Nagy G. Prolactin: structure, function, and regulation of secretion. Physiol Rev 2000; 80:1523-631. [PMID: 11015620 DOI: 10.1152/physrev.2000.80.4.1523] [Citation(s) in RCA: 1463] [Impact Index Per Article: 61.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.
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Affiliation(s)
- M E Freeman
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4340, USA.
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Fitch CA, Freeman ME. Effects of the estrous cycle stage on the prolactin secretory response to dopamine in vitro. Endocrine 1996; 4:59-63. [PMID: 21153292 DOI: 10.1007/bf02738875] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/1995] [Revised: 10/20/1995] [Accepted: 11/20/1995] [Indexed: 11/24/2022]
Abstract
Dopamine (DA) will both stimulate and inhibit prolactin (PRL) secretion from the anterior pituitary gland in vitro and in vivo. The present study was designed to determine if there are selected times during the estrous cycle of the rat when one function is favored over the other. Anterior pituitary glands collected on diestrus-1 (D1), diestrus-2 (D2), the morning of proestrus (Pro-AM), the afternoon of proestrus (Pro-PM), and estrus (E) were enzymatically dissociated and placed in monolayer culture. On the fourth day in culture, cells were challenged for 10, 20, 30, 60, 120, 180, or 240 min with media alone or media containing either 100 pM or 1 μM DA. The concentration of PRL in the media was determined by radioimmunoassay. Regression analysis revealed that in the absence of DA, PRL secretion from cultured cells differed significantly depending on the stage of the estrous cycle during which they were obtained. Cells obtained during the morning of diestrus-2 secreted PRL at the greatest rate compared to other stages of the cycle. When all stages were compared, the rates of PRL secretion were: D2>E>D1>Pro-AM>Pro-PM (each significantly different from the others,P<0.01). By 20-30 min of exposure to 100 pM DA, the rate of PRL secretion from cells obtained during each stage of the cycle was significantly enhanced. This enhanced secretion persisted in cells obtained during D2 and Pro-PM but was short-lived in cells obtained during other stages. No inhibition of PRL secretion was induced by this dose of DA. PRL secretion was inhibited when treated with 1 μM DA in cells obtained at all stages of the estrous cycle. Inhibition was more prolonged in cells obtained on D1, D2, and Pro-AM. DA was least effective as an inhibitor of PRL secretion in cells obtained during Pro-PM and E. Prior to inhibiting PRL secretion in cells obtained during Pro-PM, 1 μM DA rapidly stimulated PRL secretion. This effect persisted for 60 min. These data suggest that in the absence of DA, the dynamics of PRL secretion from anterior pituitary cells in vitro differ depending on the stage of the estrous cycle during which the cells were obtained. Moreover, the in vivo environment of the cell determines the direction and magnitude of the PRL-secretory response to DA.
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Affiliation(s)
- C A Fitch
- Department of Biological Science, Florida State University, 32306-4075, Tallahassee, FL
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12
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Omeljaniuk RJ. Specific [3H]spiperone binding sites in the pituitary of rainbow trout (Oncorhynchus mykiss) and goldfish (Carassius auratus). Can J Physiol Pharmacol 1995; 73:585-93. [PMID: 7585324 DOI: 10.1139/y95-074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dopamine, a catecholamine neurohormone, modulates pituitary hormone release in teleost fishes and other vertebrates. The existence and binding parameters of a pituitary dopamine-neuroleptic receptor from trout were examined and compared with those from goldfish. Pituitary homogenate was incubated with [3H]spiperone (D2 antagonist) under several experimental paradigms; incubations were terminated by filtration and bound 3H radioactivity was assessed by liquid scintillation spectroscopy. Specific binding of [3H]spiperone was tissue dependent. Equilibrium displacement analyses using domperidone (D2 antagonist) indicated a single class of binding site (LIGAND) with Kd = 2.49 +/- 0.89 microM and a capacity of 3.10 +/- 0.45 nmol/mg protein; the goldfish Kd and capacity were both significantly (p < 0.05) larger: Kd = 4.63 +/- 0.30 microM and capacity = 20.66 +/- 2.03 nmol/mg protein. The Kd and capacity for the trout pars distalis (2.45 +/- 0.33 microM and 3.27 +/- 0.24 nmol/mg protein, respectively) did not differ significantly (p < 0.05) from that of the neurointermediate lobe (2.50 +/- 0.08 microM and 3.58 +/- 0.56 nmol/mg protein, respectively). Dopamine D2 receptor ligands differentially displaced [3H]spiperone from the trout pituitary, while D1 ligands, a D4 ligand, and a 5-hydroxytryptamine (5HT2) receptor antagonist had only small nonspecific effects. Comparison of the trout and goldfish pituitary dopamine-neuroleptic receptor indicates conservation of receptor affinity (Kd); however, differences in receptor numbers and in the distribution of receptors between the pars distalis and neurointermediate lobe in the two species may be due in part to species or developmental differences, and may reflect differences in the role(s) and degrees of influence of dopamine in these fishes.
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Affiliation(s)
- R J Omeljaniuk
- Department of Biology, Lakehead University, Thunder Bay, ON, Canada
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13
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Zabavnik J, Wu WX, Eidne KA, McNeilly AS. Dopamine D2 receptor mRNA in the pituitary during the oestrous cycle, pregnancy and lactation in the rat. Mol Cell Endocrinol 1993; 95:121-8. [PMID: 8243802 DOI: 10.1016/0303-7207(93)90037-k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have used the technique of quantitative in situ hybridization in order to study the changes in the levels of expression of D2 receptor mRNA in the anterior pituitary gland of female rats at different stages of the reproductive cycle. Plasma prolactin levels in the same animals were determined by radioimmunoassay. Rats in the prooestrous, oestrous, dioestrous 1, dioestrous 2 phases of the oestrous cycle and in pregnant, lactating, ovariectomised and ovariectomised animals treated with diethylstilbestrol (DES) have been examined. Our results show that expression of D2 receptor mRNA in the anterior pituitary gland varies during the oestrous cycle, with the lowest expression measured during oestrus. Expression levels increased during dioestrus 1, reaching the highest values in dioestrus 2 and declining again in prooestrus. Expression of D2 receptor mRNA was reduced during pregnancy when compared to lactating animals. In ovariectomised animals, the level of D2 receptor mRNA was similar to that observed in intact animals during oestrus. Ovariectomised animals treated with DES showed dramatically increased prolactin levels, while D2 receptor mRNA remained low. Prolactin secretion might be controlled not only by variations in the release and plasma concentrations of dopamine itself, but also by modulation of D2 receptor expression in pituitary cells. Our results suggest that the variations in D2 receptor density in the anterior pituitary cells at different physiological states are, at least to some extent, regulated at the level of gene expression.
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Affiliation(s)
- J Zabavnik
- MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, UK
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14
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Hallonquist JD, Seeman MV, Lang M, Rector NA. Variation in symptom severity over the menstrual cycle of schizophrenics. Biol Psychiatry 1993; 33:207-9. [PMID: 8448269 DOI: 10.1016/0006-3223(93)90141-y] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- J D Hallonquist
- Department of Psychiatry, Mount Sinai Hospital, Toronto, Ontario, Canada
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15
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Pasqualini C, Sarrieau A, Dussaillant M, Corbani M, Bojda-Diolez F, Rostène W, Kerdelhué B. Estrogen-like effects of 7,12-dimethylbenz(a)anthracene on the female rat hypothalamo-pituitary axis. JOURNAL OF STEROID BIOCHEMISTRY 1990; 36:485-91. [PMID: 2145477 DOI: 10.1016/0022-4731(90)90092-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have recently demonstrated that 7,12-dimethylbenz(a)anthracene (DMBA), a potent inducer of mammary tumors in rodents, can in vitro decrease the number of membrane dopamine D2 receptors and stimulate prolactin (PRL) release, by direct estrogen-like actions on anterior pituitary. In the present study, we tested the ability of DMBA to mimic the in vivo estradiol (17 beta E2) effects on pituitary D2 receptors and on PRL as well as LH release. We have found that DMBA, like 17 beta E2, when injected to ovariectomized rats, induced a decrease in the number of anterior pituitary D2 receptors, a release of PRL and exerted a biphasic (acute negative and longer term positive) action on LH secretion. We thus examined the ability of DMBA to interact with 17 beta E2 receptors in the hypothalamo-pituitary axis: DMBA binds to the pituitary cytosolic estrogen receptors with an affinity 0.001% that of 17 beta E2. Finally [3H]DMBA binds to hypothalamus-containing brain sections. This binding was displaced partially by RU 2858 a pure estrogen agonist and totally by tamoxifen, a purported estrogen antagonist. No competition for [3H]DMBA binding was observed with an androgen (RU 1881) or a glucocorticoid (RU 26988) agonist. From these data, it may be concluded that DMBA can act as a partial estrogen in pituitary and hypothalamic tissues.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/metabolism
- 9,10-Dimethyl-1,2-benzanthracene/pharmacology
- Animals
- Binding Sites
- Binding, Competitive
- Brain/metabolism
- Cytosol/metabolism
- Estrogens
- Female
- Hypothalamo-Hypophyseal System/drug effects
- Kinetics
- Luteinizing Hormone/blood
- Luteinizing Hormone/metabolism
- Pituitary Gland, Anterior/drug effects
- Pituitary Gland, Anterior/metabolism
- Prolactin/blood
- Prolactin/metabolism
- Rats
- Rats, Inbred Strains
- Receptors, Dopamine/drug effects
- Receptors, Dopamine/metabolism
- Receptors, Dopamine D2
- Receptors, Estradiol/drug effects
- Receptors, Estradiol/metabolism
- Reference Values
- Spiperone/metabolism
- Tamoxifen/metabolism
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Affiliation(s)
- C Pasqualini
- Laboratoire de Neurobiologie de la Reproduction, CNRS-INRA, Jouy-en-Josas, France
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16
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Arushanyan EB, Borovkova GK. Psychotropic properties of ovarian estrogens (review). NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1989; 19:57-66. [PMID: 2664552 DOI: 10.1007/bf01148412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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17
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Ferretti C, Blengio M, Ghi P, Racca S, Genazzani E, Portaleone P. Tamoxifen counteracts estradiol induced effects on striatal and hypophyseal dopamine receptors. Life Sci 1988; 42:2457-65. [PMID: 3374265 DOI: 10.1016/0024-3205(88)90344-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
UNLABELLED We investigated the ability of Tamoxifen (TAM), an antiestrogen drug, to counteract the modifications induced by estrogens on dopamine (DA) receptors on striatum and on adenohypophysis of ovex female rats. Subacute treatment with 17 beta-estradiol (E2) at both low (0.1 micrograms/kg) and high (20 micrograms/kg) doses confirmed its ability to increase the number of striatal 3H-Spiperone (3H-SPI) binding sites in a dose dependent manner. By contrast in the pituitary, only high doses of estrogen were effective in reducing the number of DA receptors. We treated ovex female rats for 15 days with TAM alone or associated with E2, to see if these estrogenic effects could be suppressed by an antiestrogenic drug. TAM did not affect the number of striatal DA receptors, but significantly increased the adenohypophyseal DA binding sites, without varying their affinity. No changes were observed in pituitary and striatal DA receptor density, even when TAM was injected in association with estradiol. IN CONCLUSION TAM is able to counteract the effects estrogens have on DA receptors. However there is some evidence that it could influence the pituitary DA systems independently of its antiestrogenic activity.
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Affiliation(s)
- C Ferretti
- Institute of Pharmacology, Medical School, University of Turin, Italy
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18
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Welch MJ, Katzenellenbogen JA, Mathias CJ, Brodack JW, Carlson KE, Chi DY, Dence CS, Kilbourn MR, Perlmutter JS, Raichle ME. N-(3-[18F]fluoropropyl)-spiperone: the preferred 18F labeled spiperone analog for positron emission tomographic studies of the dopamine receptor. INTERNATIONAL JOURNAL OF RADIATION APPLICATIONS AND INSTRUMENTATION. PART B, NUCLEAR MEDICINE AND BIOLOGY 1988; 15:83-97. [PMID: 3258305 DOI: 10.1016/0883-2897(88)90164-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The ligands currently used for PET studies of the dopamine receptor are fluorine-18-labeled spiperone (FSp) and carbon-11 or fluorine-18-labeled N-methyl-spiperone. All three of these ligands have drawbacks in either their chemical preparation or their biological behavior. We have previously prepared a series of N-fluoroalkyl-spiperone derivatives which are simple to prepare in high radiochemical yield. N-[18F]fluoropropyl-spiperone (3-F-Pr-Sp) and N-[18F]fluoroethyl-spiperone (2-F-Et-Sp) were the most promising ligands. In vitro competitive binding studies showed affinities for the dopamine receptor of 3-F-Pr-Sp greater than FSp greater than 2-F-Et-Sp. Brain extraction studies in a primate model showed that FSp, 2-F-Et-Sp, and 3-F-Pr-Sp were not completely extracted by the brain. High bone uptake and kidney clearance was observed with 3-F-Pr-Sp, while 2-F-Et-Sp cleared through the intestine in rats. This is in contrast to FSp where clearance is through the kidney. Studies to evaluate the extraction of metabolites in the brain were carried out by administering large doses (10 mCi) of FSp, 2-F-Et-Sp and 3-F-Pr-Sp to rats and reinjecting the metabolites in blood into other rats. These experiments showed that less than 0.02% of the metabolites from FSp and 3-F-Pr-Sp entered the brain, while 0.5% of the metabolites from 2-F-Et-Sp entered the brain. The majority of the activity present in the cerebellum after the administration of 2-F-Et-Sp is metabolites; therefore 2-F-Et-Sp is unsuitable for PET imaging studies. PET imaging studies in baboons and in one normal human volunteer with 3-F-Pr-Sp showed a high striatum-to-cerebellum ratio, showing that 3-F-Pr-Sp can replace ligands currently in use to study dopamine receptors.
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Affiliation(s)
- M J Welch
- Division of Radiation Sciences, Washington University School of Medicine, St Louis, MO 63110
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19
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Di Paolo T, Falardeau P, Morissette M. Striatal D-2 dopamine agonist binding sites fluctuate during the rat estrous cycle. Life Sci 1988; 43:665-72. [PMID: 3412110 DOI: 10.1016/0024-3205(88)90137-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Striatal D-2 dopamine (DA) antagonist and agonist binding sites were measured during the rat estrous cycle and compared to ovariectomized (OVX) rats. Dopaminergic D-2 antagonist binding sites were constant during the estrous cycle while agonist binding sites show a rapid and significant decrease of the ratio of high to low D-2 agonist binding sites from proestrus AM (PAM) to diestrus 1 (D1) and return to OVX value in diestrus 2 (DII). Thus, physiological fluctuations of hormones as occur during the estrous cycle can modulate extrahypothalamic biogenic amine activity, namely striatal DA systems which are not involved in the control of hormone secretion.
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Affiliation(s)
- T Di Paolo
- School of Pharmacy, Laval University Ste-Foy, Québec, Canada
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20
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Enjalbert A, Bertrand P, Bockaert J, Drouva S, Kordon C. Multiple coupling of neurohormone receptors with cyclic AMP and inositol phosphate production in anterior pituitary cells. Biochimie 1987; 69:271-9. [PMID: 2820513 DOI: 10.1016/0300-9084(87)90017-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Regulation of adenohypophyseal hormone secretions has been shown to involve cyclic AMP production, modulation of phosphatidyl inositol diphosphate breakdown and Ca2+ mobilization. Various neurohormone receptors are positively or negatively coupled to adenylate cyclase activity in anterior pituitary cells. The effects of these neurohormones on adenylate cyclase activity are consistent with the effect on hormone secretions, suggesting that modulation of the enzyme activity is actually involved in the regulation of adenohypophyseal secretions. Thus DA inhibits, whereas VIP stimulates adenylate cyclase activity of the same cell type, which, according to the effect of these neurohormones on prolactin secretion, appear to be lactotrophs. On the other hand, SRIF inhibits, whereas GRF stimulates the adenylate cyclase activity of another cell type, namely somatotrophs, whereas CRF appears to act on a third cell type, corticotrophs. Peripheral hormones have been shown to modulate the sensitivity of anterior pituitary cells to these neurohormones. Estradiol long-term treatment has an anti-dopaminergic effect on prolactin secretion. The steroid also suppresses the dopamine inhibition of adenylate cyclase. This effect appears selective to the DA inhibition, since AII inhibition of the enzyme is only partially reduced, whereas the somatostatin inhibition is markedly increased. Peripheral hormones seem to affect the sensitivity of adenohypophyseal cells not only by modulating the number of receptors for a given neurohormone but also by interfering with the coupling mechanisms of these receptors. AII and DA inhibit the adenylate cyclase activity of lactotroph cells. The prolactin stimulation induced by angiotensin is not consistent with the effect of the peptide on adenylate cyclase.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Enjalbert
- INSERM U159, Neuroendocrinologie, Centre Paul-Broca, Paris, France
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21
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Ramos JA, Pais JR, Cebeira M, Fernandez-Ruiz J. Role of estrogens on striatal dopaminergic activity. JOURNAL OF STEROID BIOCHEMISTRY 1987; 27:683-9. [PMID: 2961941 DOI: 10.1016/0022-4731(87)90137-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Studies were undertaken to evaluate the effects of estradiol and prolactin on striatal dopamine receptor activity. Dopamine receptors were quantified in partially purified striatal membranes by equilibrium binding using [3H]spiroperidol. When we investigated whether the D-2 dopamine receptor activity changes during the estrous cycle, the results suggest an increase in dopamine receptor density in diestrous, without modifications in the affinity. The finding that in ovariectomized rats the dopamine receptor binding parameters remained unchanged, suggests that gonadal steroids are not essential in the mechanism of action of this receptor. Results of activity of D-2 dopamine receptors showing that hyperprolactinemia fails to increase the number of these receptors do not support the hypothesis that circulating prolactin regulates the activity of these striatal dopamine receptors. Administration of estradiol benzoate (250 micrograms/kg per day) to hyperprolactinemic rats, by s.c. injection, significantly decreased both the density and the affinity of the striatal dopamine receptors. The present data indicate that, although prolactin does not seem to modify the activity of striatal dopamine receptors, it could modulate the estrogen-induced hypersensitivity of these receptors.
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Affiliation(s)
- J A Ramos
- Department of Biochemistry, School of Medicine, Complutensis University, Madrid, Spain
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22
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Petrovic SL, McDonald JK, De Castro JC, Snyder GD, McCann SM. Regulation of anterior pituitary and brain beta-adrenergic receptors by ovarian steroids. Life Sci 1985; 37:1563-70. [PMID: 2997565 DOI: 10.1016/0024-3205(85)90474-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Ovariectomy of adult female rats (200-230g) resulted in an increase in beta-adrenergic receptors in the cerebral cortex, hypothalamus and anterior pituitary. The anterior pituitary had the largest overall increase as well as the most rapid increase in beta-adrenergic receptor density of the tissues examined. The increase in hypothalamic or cerebral cortical beta-adrenergic receptors became apparent only long after ovariectomy (7-14 days). Fourteen days after ovariectomy, the density of beta-adrenergic receptors was 79%, 40%, and 24% in excess of control values in crude membranes prepared from anterior pituitary, hypothalamus and cerebral cortex, respectively. Over the same interval, the plasma concentration of luteinizing hormone (LH) increased 28-fold, while the concentration of follicle-stimulating hormone (FSH) rose 5-fold compared to control levels. Estradiol replacement (20 micrograms/kg/day) in these animals for four days before sacrifice concomitantly reduced plasma levels of the gonadotropins as well as the density of beta-adrenergic receptors in both the anterior pituitary and the hypothalamus. Long-term steroid replacement during the fifth and sixth week after ovariectomy, with implants of estradiol and progesterone which released the steroids in approximately physiological concentrations, significantly reduced beta-adrenergic density in anterior pituitary, but not in the hypothalamic membranes. This treatment significantly reduced plasma LH, but not FSH. Beta-adrenergic receptor density was also found to fluctuate significantly during the 4-day estrous cycle. The highest values were found on proestrus, and the lowest on diestrus 1. These studies indicate that changes in plasma concentrations of gonadal steroids (e.g. during the estrous cycle) influence the density of beta-adrenergic receptors in tissues involved in the control and release of anterior pituitary gonadotropins.
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23
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Pazos A, Stoeckel ME, Hindelang C, Palacios JM. Autoradiographic studies on dopamine D2 receptors in rat pituitary: influence of hormonal states. Neurosci Lett 1985; 59:1-7. [PMID: 2931628 DOI: 10.1016/0304-3940(85)90206-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The influence of the estrous cycle on the density of dopamine D2 sites in the rat pituitary was studied by quantitative autoradiography using [3H]spiperone. While no significant changes were found in the neural and intermediate lobes during the cycle, a lower number of D2 receptors in the anterior lobe was observed in the proestrus when compared to the diestrus. The difference in the density of [3H]spiperone binding in the pituitary between male and female rats was also analysed. A significantly lower number of receptors in the three lobes of the male pituitary, as compared to those of the female, was found. Finally, no significant variation in the number of binding sites in the 3 pituitary lobes was observed between lactating and separated mothers.
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24
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Ali SF, Peck EJ. Modulation of anterior pituitary dopamine receptors by estradiol 17-beta: dose-response relationship. J Neurosci Res 1985; 13:497-507. [PMID: 4009741 DOI: 10.1002/jnr.490130404] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Exposure of ovariectomized rats to estradiol-17-beta for 48-96 hr resulted in a dose-dependent reduction in the number but not the Kd of D-2 dopamine receptors of the anterior pituitary. No influence of estrogen was observed on dopamine or muscarinic acetylcholine receptors of caudate or hypothalamus. The dose-response relationship observed suggested that the influence of estrogen is directly on the pituitary, not secondary to the alteration of dopaminergic systems in the hypothalamus.
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25
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Di Paolo T, Falardeau P. Modulation of brain and pituitary dopamine receptors by estrogens and prolactin. Prog Neuropsychopharmacol Biol Psychiatry 1985; 9:473-80. [PMID: 4089182 DOI: 10.1016/0278-5846(85)90004-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ovariectomized rats were treated for 2 weeks with 17 beta-estradiol (0.0002-100 micrograms/day). [3H]spiperone striatal dopamine receptor binding was maximally increased by 30% after 0.05 micrograms/day of 17 beta-estradiol and a similar increase is observed at higher doses. By contrast, plasma prolactin concentrations of these rats are unchanged after 0.05 micrograms/day and increased after 100 micrograms/day. A chronic estradiol treatment at very low doses (0.0002-0.001 microgram/day) leads to increases in pituitary dopamine receptor binding while plasma prolactin levels are unchanged. At higher doses (1-100 micrograms/day) binding is decreased and plasma prolactin concentrations are elevated. [3H]spiperone striatal dopamine receptor binding is elevated in lactating female rats compared to intact or ovariectomized female rats. Anterior pituitary dopamine receptor concentrations fluctuate during the estrous cycle while striatal dopamine receptors are unchanged. An injection of 30 ng of estradiol, which reproduces the estradiol proestrus surge, leads as in proestrus, to a decrease of anterior pituitary dopamine receptors.
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