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Li H, Zhang Y, Deng Z, Lu B, Ma L, Wang R, Wang X, Jiao Z, Wang Y, Zhou K, Wei Q. Constructing a Hydrophilic Microsensor for High-Antifouling Neurotransmitter Dopamine Sensing. ACS Sens 2024. [PMID: 38384144 DOI: 10.1021/acssensors.3c02042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9°, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 μA μM-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 μM in rat brains upon 2 μL of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.
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Affiliation(s)
- Haichao Li
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Yening Zhang
- Department of Hematology and Critical Care Medicine, The Third Xiangya Hospital, Central South University, Changsha, Hunan Province 410000, P. R. China
- Key Laboratory of Sepsis Translational Medicine of Hunan, Central South University, Changsha, Hunan Province 410000, P. R. China
| | - Zejun Deng
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Ben Lu
- Department of Hematology and Critical Care Medicine, The Third Xiangya Hospital, Central South University, Changsha, Hunan Province 410000, P. R. China
- Key Laboratory of Sepsis Translational Medicine of Hunan, Central South University, Changsha, Hunan Province 410000, P. R. China
| | - Li Ma
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Run Wang
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Xiang Wang
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Zengkai Jiao
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Yijia Wang
- Institute for Advanced Study, Central South University, Changsha 410083, P. R. China
| | - Kechao Zhou
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
| | - Qiuping Wei
- State Key Laboratory of Powder Metallurgy, School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
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Short-term fasting decreases excitatory synaptic inputs to ventromedial tuberoinfundibular dopaminergic neurons and attenuates their activity in male mice. Neurosci Lett 2018; 671:70-75. [DOI: 10.1016/j.neulet.2018.02.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/01/2018] [Accepted: 02/08/2018] [Indexed: 01/03/2023]
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3
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Two dimensional palladium nanoparticle assemblies as electrochemical dopamine sensors. Inorganica Chim Acta 2017. [DOI: 10.1016/j.ica.2017.08.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Jiang L, Nelson GW, Abda J, Foord JS. Novel Modifications to Carbon-Based Electrodes to Improve the Electrochemical Detection of Dopamine. ACS APPLIED MATERIALS & INTERFACES 2016; 8:28338-28348. [PMID: 27420730 DOI: 10.1021/acsami.6b03879] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this work, we describe three simple modifications to carbon electrodes that were found to improve the detection of an exemplar neurotransmitter (dopamine) in the presence of physiological interferents (ascorbic acid and/or uric acid). First, the electro-oxidation of ascorbic acid, as a pretreatment, at boron-doped diamond electrode (BDE) interfaces is studied. This treatment did suppress the detection of ascorbic acid oxidation signal, but only in a manner suitable for single-use detection of high concentrations of dopamine (i.e., > 1 μM). Second, the hydrogenation of BDE by electrochemical cathodic treatment and plasma hydrogenation was investigated. Large cathodic, applied potentials (i.e., > - 5 V) and hydrogen plasma pretreatment of BDE lead to the partial and complete oxidization of ascorbic acid before dopamine, respectively. The consequence at hydrogen-plasma treated BDE is the complete electrochemical separation of these two species without any typical catalytic reactions between the analytes. Third, the modification of glassy carbon electrodes with carbon black nanoparticles is explored. This modification enables the simultaneous detection of ascorbic acid, dopamine and uric acid, significantly enhancing the sensitivity of dopamine. Dopamine was best detected using the unconventional route of detecting 5,6-dihydroxyindole, which is made possible by use of carbon-black nanoparticles. The potential of all three studied modifications to be of electroanalytical use is highlighted throughout this work.
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Affiliation(s)
- Luyun Jiang
- Chemical Research Laboratory, University of Oxford , 12 Mansfield Road, Oxford, United Kingdom OX13TA
| | - Geoffrey W Nelson
- Chemical Research Laboratory, University of Oxford , 12 Mansfield Road, Oxford, United Kingdom OX13TA
| | - Julia Abda
- Chemical Research Laboratory, University of Oxford , 12 Mansfield Road, Oxford, United Kingdom OX13TA
| | - John S Foord
- Chemical Research Laboratory, University of Oxford , 12 Mansfield Road, Oxford, United Kingdom OX13TA
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Kim CH, Kim HY, Lee HS, Choi BY, Chang SO, Oh SH, Lee JH. Dopamine increases Na+ absorption in the Reissner's membrane of the gerbil cochlea. Auris Nasus Larynx 2012; 40:266-72. [PMID: 23058482 DOI: 10.1016/j.anl.2012.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/27/2012] [Accepted: 09/14/2012] [Indexed: 01/11/2023]
Abstract
OBJECTIVE The purpose of the present study was to investigate the effect of dopamine as a possible regulator of epithelial Na(+) channel (ENaC) in the Reissner's membrane (RM). METHODS RM was freshly dissected from the gerbil cochlea, and short-circuit current (Isc) was measured using the voltage-sensitive vibrating probe technique. The dopamine receptor expression was examined using immunohistochemistry. RESULTS The results showed that dopamine induced activation of the amiloride-sensitive Isc, but not after pre-treatment with amiloride. The D1-like receptor antagonist SCH-23390, but not the D2-like receptor antagonist sulpiride, decreased the stimulatory effect of dopamine on RM. The effect of dopamine on Na(+) transport via ENaC was still observed after blockade of the Na(+)-K(+)-ATPase by ouabain. D1 receptor immunoreactivity was observed in RM, stria vascularis and spiral ganglion. CONCLUSION Na(+) transport in RM is activated by dopamine possibly via D1-like receptors, and intracellular mechanisms other than cAMP-mediated pathway may be involved.
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Affiliation(s)
- Chang-Hee Kim
- Department of Otorhinolaryngology-Head and Neck Surgery, Konkuk University School of Medicine, Republic of Korea
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Goldman JM, Stoker TE, Murr AS, McElroy WK, Cooper RL. Regional differences in the pituitary distribution of luteinizing hormone in the gonadectomized and proestrous female rat. Gen Comp Endocrinol 2008; 156:577-83. [PMID: 18395720 DOI: 10.1016/j.ygcen.2008.02.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 02/12/2008] [Accepted: 02/25/2008] [Indexed: 10/22/2022]
Abstract
Previous data have shown that regional differences in the presence of anterior pituitary luteinizing hormone (LH) generally correlate with the comparable disparities in distribution of gonadotropes throughout the gland. In female rats, the differences are apparent over the estrous cycle, but are more prominent during the hours preceding the proestrus surge of LH. The current experiments examined (1) if such regional disparities are present throughout the surge window, (2) if differences are mirrored by release of LH in vitro and (3) if the appearance of regional differences is altered in ovariectomized females. Results showed that a comparative elevation in the rostral portion of the pituitary during the pre-surge period diminishes and finally disappears concurrent with the rise in circulating LH. This increase in rostral LH concentrations is reflected in this region by a comparable effect in vitro on stimulated LH secretion from pituitary fragments, although the effect is somewhat diminished by referencing release against tissue concentrations of LH present in a contralateral rostral fragment. Ovariectomies conducted at 1500h on proestrus, at a time when a significant regional difference has faded, resulted in a prompt increase in LH across all areas of the pituitary, and the emergence of a marked augmentation in rostral concentrations over the ensuing 72h. The effect was not seen when ovariectomies were performed on estrus. These data show that, while a regional disparity in anterior pituitary LH is present as circulating concentrations of estradiol rise prior to the LH surge, the removal of this steroid feedback at a time when LH synthesis is normally amplified accentuates the difference between the rostral region and other areas of the pituitary.
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Affiliation(s)
- J M Goldman
- Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Johnston JD, Stirland JA, White MRH, Davis JRE, Loudon ASI. Heterogeneous regulation of individual lactotroph cells by photoperiod in the Syrian hamster (Mesocricetus auratus). Gen Comp Endocrinol 2003; 134:182-6. [PMID: 14511989 DOI: 10.1016/s0016-6480(03)00248-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In many mammals, changes in daylength (photoperiod) regulate multiple aspects of physiology, including the synthesis and secretion of the anterior pituitary hormone prolactin. Here, we tested the hypothesis that individual lactotroph cells exhibit a heterogeneous response to changes in photoperiod, by exploiting a recently developed assay for prolactin gene expression in single pars distalis (PD) cells. Male Syrian hamsters were exposed to either long (LD; 16 h light: 8 h dark) or short (SD; 8 h light: 16 h dark) photoperiods for 12 weeks. Response of the lactotrophic axis to photoperiod was confirmed by the significantly (P<0.01) lower plasma prolactin concentrations in SD than LD hamsters. Analysis of freshly dispersed PD cells by in situ hybridisation demonstrated that photoperiod has no effect (P>0.05) on the proportion of PD cells (approximately 25%) that expressed prolactin mRNA. Heterogeneity of prolactin mRNA expression was observed in both LD and SD. A similar proportion of cells expressed low levels of prolactin mRNA in both photoperiods, suggesting that they may be unresponsive to photoperiod change. In contrast, the remaining PD cells that expressed prolactin mRNA exhibited markedly increased gene expression in LD, consistent with the selective recruitment of a lactotroph subpopulation to a more transcriptionally active state in this photoperiod.
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8
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Hentschel K, Moore KE, Lookingland KJ. Effects of prolactin on expression of Fos-related antigens in tyrosine hydroxylase-immunoreactive neurons in subdivisions of the arcuate nucleus. Brain Res 2000; 857:110-8. [PMID: 10700558 DOI: 10.1016/s0006-8993(99)02362-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Dual immunohistochemistry was employed to determine the effects of prolactin on expression of Fos and its related antigens (FRA) in tuberoinfundibular dopamine (TIDA) neurons located in the dorsomedial (DM) and ventrolateral (VL) subdivisions of the arcuate nucleus (ARC) in the male rat. Systemic administration of the DA receptor antagonist haloperidol caused a sustained (up to 12 h) increase in plasma prolactin concentrations that was accompanied by a transient increase (at 3 h) in the percentage of tyrosine hydroxylase (TH)-immunoreactive (IR) neurons containing FRA-IR nuclei in the DM-ARC. In contrast, haloperidol caused a prolonged (1. 5 to 12 h) decrease in the percentage of TH-IR neurons with FRA-IR nuclei in the VL-ARC. Haloperidol had no effect, however, on the overall number of TH-IR neurons in either of these regions. Co-administration of prolactin antisera (PRL-AB) blocked haloperidol-induced increases in both plasma prolactin concentrations and the percentage of TH-IR neurons expressing FRA in the DM-ARC, but had no effect on haloperidol-induced inhibition of FRA expression in TH-IR neurons in the VL-ARC. Intracerebroventricular (i.c.v.) administration of prolactin also increased the percentage of TH-IR neurons containing FRA-IR nuclei in the DM-ARC, but this effect was of longer duration (up to 6 h) than that of haloperidol in all but the most caudal portion of the DM-ARC. In the VL-ARC, prolactin caused a transient increase (at 1.5 h) in the percentage of TH-IR containing FRA-IR nuclei. These results demonstrate that prolactin regulates immediate early gene expression in TIDA neurons in male rats, and reveal that there are temporal differences in the responsiveness of discrete subpopulations of these neurons to prolactin. Prolactin causes a short-lived increase in FRA expression in TIDA neurons in the VL-ARC which is followed by a more prolonged activation of FRA expression in TIDA neurons in the DM-ARC.
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Affiliation(s)
- K Hentschel
- Department of Pharmacology and Toxicology, Michigan State University, B-432 Life Sciences Bldg., East Lansing, MI 48824-1317, USA
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Engler D, Redei E, Kola I. The corticotropin-release inhibitory factor hypothesis: a review of the evidence for the existence of inhibitory as well as stimulatory hypophysiotropic regulation of adrenocorticotropin secretion and biosynthesis. Endocr Rev 1999; 20:460-500. [PMID: 10453355 DOI: 10.1210/edrv.20.4.0376] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- D Engler
- Laboratory of Molecular Genetics and Development, Institute of Reproduction and Development, Monash Medical Centre, Clayton, Victoria, Australia
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10
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Abraham EJ, Faught WJ, Frawley LS. Transforming growth factor beta1 is a paracrine inhibitor of prolactin gene expression. Endocrinology 1998; 139:5174-81. [PMID: 9832458 DOI: 10.1210/endo.139.12.6349] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have shown previously that rat mammotropes produce an activity that suppresses PRL gene expression by neighboring mammotropes. Here, we tested the hypothesis that this mammotrope-derived inhibitor is transforming growth factor-beta1 (TGFbeta1). To this end, we pursued a two-pronged strategy wherein we added exogenous TGFbeta1 to primary cultures of anterior pituitary cells transfected with a rat PRL-luc construct. Measurement of luciferase activity by luminometry of extracts revealed that administration of TGFbeta1, over a range of doses shown by others to be secreted by cultures of pituitary cells, caused a significant (P < 0.05) suppression of PRL gene expression. In contrast, immunoremoval of secreted TGFbeta1 led to an elevation of PRL promoter-driven reporter activity in these cultures. In a subsequent study, we repeated these experiments with a single cell model in an attempt to determine the demographics of the cellular responses. Accordingly, we transfected (via microinjection) individual mammotropes with the rat PRL-luc construct; exposed them to TGFbeta1, its neutralizing antibody, or respective controls; and then assessed PRL gene expression in "real-time" by quantification of photons emitted by the living cells after exposure to the substrate luciferin. Our results revealed that 1) TGFbeta1 inhibited PRL gene expression in all mammotrope studied; 2) only a subgroup of mammotropes (approximately 23%) was relieved of TGFbeta1 inhibition by antibody treatment; and 3) the growth factor exerted its inhibitory effect via a paracrine, as opposed to an autocrine, mechanism. These findings identify TGFbeta1 as the paracrine agent that exerts a tonic inhibitory influence over PRL gene expression in mammotropes.
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Affiliation(s)
- E J Abraham
- Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston 29425, USA
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11
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Anthony EL, Overdeep PA, Bruhn TO, Gustafson AW. Evidence for diverse pathways of hypophysiotropic hormone transport in mammals. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1998; 119:365-74. [PMID: 9827008 DOI: 10.1016/s0742-8413(98)00024-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Comparative studies of mammalian hypothalamic-pituitary relationships have revealed striking variations in hypophysiotropic systems and in portal vascular architecture. Immunocytochemical studies indicate that mammalian GnRH, GHRH and somatostatin systems can project to all portions of the neurohypophysis (median eminence, infundibular stem and pituitary neural lobe). In rats, primary secretion sites are located within the median eminence and upper infundibular stem, whereas in bats, most projections extend into the lower infundibular stem and pituitary neural lobe. In ferrets and monkeys, sites of secretion appear to extend throughout the neurohypophysis, from median eminence to proximal neural lobe. In this review, these interspecific differences are examined in light of observed structural variations in portal vascular systems. Correlations suggest that hypophysiotropic hormones can be delivered to target cells in the pars distalis by diverse routes, with some species relying more heavily on long and others on short portal transport. These patterns may have important functional implications with respect to regulatory mechanisms operating within the hypothalamic-pituitary complex.
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Affiliation(s)
- E L Anthony
- Department of Biology, Rhode Island College, Providence 02908, USA.
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12
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Cheung S, Will YM, Hentschel K, Moore KE, Lookingland KJ. Role of gonadal steroids in determining sexual differences in expression of Fos-related antigens in tyrosine hydroxylase-immunoreactive neurons in subdivisions of the hypothalamic arcuate nucleus. Endocrinology 1997; 138:3804-10. [PMID: 9275068 DOI: 10.1210/endo.138.9.5411] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Dual immunohistochemistry was employed to examine the role of gonadal steroids in determining sexual differences in the expression of Fos and its related antigens (FRA) in tuberoinfundibular dopaminergic (TIDA) neurons located in the dorsomedial (DM-) and ventrolateral (VL-) subdivisions of the arcuate nucleus (ARC). In the DM-ARC, there was no sexual difference in the number of tyrosine hydroxylase (TH)-immunoreactive (-IR) perikarya, but the number of these containing FRA-IR was greater in females than in males in all but the most caudal region. In the VL-ARC, there were more TH-IR perikarya in males than in females, but there was no sexual difference in the numbers of those containing FRA-IR throughout the entire rostrocaudal extent of this nucleus. Ovariectomy decreased the number of TH-IR perikarya containing FRA-IR in the DM-ARC, but not in the VL-ARC, whereas orchidectomy increased the number of TH-IR perikayra containing FRA-IR in both the DM-ARC and VL-ARC. These gonadectomy-induced effects were reversed by estrogen and testosterone, respectively. These results reveal gonadal steroid-dependent sexual differences in the regulation of immediate early gene expression in anatomically discrete subpopulations of TIDA neurons. In females, estrogen stimulates FRA expression in TIDA neurons in the DM-ARC, whereas in males, testosterone inhibits FRA expression in TIDA neurons in both the DM-ARC and the VL-ARC.
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Affiliation(s)
- S Cheung
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824-1317, USA.
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Poole MC, Easley CS, Hodson CA. Alteration of the mammotroph Golgi complex by the dopamine agonist 2 Br-alpha-ergocryptine (CB-154) in ovariectomized estrogen primed rats. Anat Rec (Hoboken) 1991; 231:339-46. [PMID: 1763815 DOI: 10.1002/ar.1092310307] [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: 12/28/2022]
Abstract
The present study examined the acute effects of 2 Br-alpha-ergocryptine (CB-154, a dopamine agonist) on mammotroph organelles during prolactin (PRL) suppression. Ovariectomized estrogen-primed rats received a single injection (sc) of 0.5 mg CB-154 and the animals were killed at intervals following injection. The anterior pituitary glands were fixed for electron microscopy and immunocytochemistry was used to confirm mammotroph identification. Serum PRL levels were determined by RIA. Following CB-154 administration, serum PRL was significantly (P less than 0.05) reduced within 15 minutes and was suppressed (P less than 0.01) to ovariectomized levels at 2 and 6 hours. A stereological analysis of mammotrophs in the central regions of the anterior pituitary showed that the Golgi complex volume was significantly (P less than 0.05) reduced at 2 hours after CB-154 treatment. However, the Golgi complex volume had recovered by 6 hours post CB-154 injection. In addition, the volumes of the mammotroph cells, the mature secretory granules, and the secondary lysosomes had significantly increased by 6 hours. There were no significant changes in any of the organelles following CB-154 in the mammotrophs from the peripheral regions of the gland. These studies show that the Golgi complex is especially susceptible to acute morphological changes induced by bromocryptine and that the mammotrophs in the central regions are more responsive to CB-154 than those in the peripheral regions.
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Affiliation(s)
- M C Poole
- Department of Anatomy and Cell Biology, School of Medicine, East Carolina University, Greenville, North Carolina 27858
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Terzolo M, Piovesan A, Osella G, Torta M, Buniva T, Paccotti P, Wierdis T, Angeli A. Exogenous melatonin enhances the TRH-induced prolactin release in normally cycling women: a sex-specific effect. Gynecol Endocrinol 1991; 5:83-94. [PMID: 1656706 DOI: 10.3109/09513599109028431] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The aim of the present study was to analyze the effects of exogenous melatonin (MT) upon pituitary and adrenal responsiveness to releasing hormones in different phases of the menstrual cycle. We evaluated the response of FSH and LH to 100 micrograms gonadotropin releasing hormone, of TSH and prolactin (PRL) to 200 micrograms thyrotropin releasing hormone (TRH), and of cortisol to 10 micrograms ACTH 1-17. We studied eight young women with normal ovulatory cycles in the early follicular (days 5-7) and luteal (days 22-24) phases. Stimulation tests were performed at 18.00 in baseline conditions as well as 1 h after oral intake of exogenous MT (2 mg as a gelatine capsule). We did not observe any significant change in FSH, LH, TSH and cortisol responses to their respective releasing hormones in either phase of the cycle. PRL response to TRH was higher after MT in the follicular phase, when evaluated in terms of net increment and integrated area of response (p less than 0.02 versus baseline conditions for both variables). In the luteal phase, we recorded larger interindividual variability and higher responses after MT were observed in five out of eight subjects. These results suggest that MT may play a facilitatory role in the TRH-induced PRL release in women of reproductive age.
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Affiliation(s)
- M Terzolo
- Università degli Studi di Torino, Dipartimento di Scienze Cliniche e Biologiche, Ospedale S. Luigi Gonzaga, Turin, Italy
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15
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Mukherjee P, Salada T, Hymer WC. Function of prolactin cells in the individual rat pituitary gland is location dependent. Mol Cell Endocrinol 1991; 76:35-44. [PMID: 1820975 DOI: 10.1016/0303-7207(91)90257-s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Anterior pituitary glands from individual ovariectomized (ovx) or ovx-estrogen (E2) treated rats were sectioned into 1/8 cubes. Each section was incubated for four consecutive 15 min periods in order to measure the release of immunoreactive and bioactive prolactin (PRL); each individual section was then trypsinized into a single cell suspension for determination of PRL cell numbers in that section. Hormone release (ng PRL/1000 PRL cells) was not uniform throughout the gland; the consistency of the secretory patterns demonstrated that the amount of PRL release from the gland was location-dependent. Statistical analysis of the data showed that the most active cells were in the gland's left lobe, while the least active were in the right lobe. Within these lobes, the dorsal-caudal and ventral-rostral left lobe areas released the most hormone in vitro while those in the dorsal-rostral, dorsal-caudal and ventral-rostral right lobe areas were least active. Injection of ovx rats with E2 for 2 days altered these secretory patterns. This sectioning procedure should prove useful in future studies addressing issues of cell-cell interaction and geographic location as they relate to pituitary cell function.
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Affiliation(s)
- P Mukherjee
- Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802
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Camanni F, Ciccarelli E, Ghigo E, Müller EE. Hyperprolactinemia: neuroendocrine and diagnostic aspects. J Endocrinol Invest 1989; 12:653-68. [PMID: 2685096 DOI: 10.1007/bf03350030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- F Camanni
- Dipartimento di Fisiopatologia clinica, Università di Torino, Italy
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Paradisi R, Frank G, Grossi G, Venturoli S, Porcu E, Capelli M, Galassi E, Flamigni C. High concentrations of catecholamines in human hypothalamic-hypophysial blood. J Clin Invest 1989; 83:2079-84. [PMID: 2723073 PMCID: PMC303934 DOI: 10.1172/jci114120] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
While the hypothalamic-hypophysial portal system has been extensively studied in laboratory animals, equivalent studies have not been performed in humans. Here, we present an experimental procedure for collecting suprapituitary blood in man. To solve the question on the origin of such blood we investigated specific markers of hypothalamic secretory activity: the catecholamines (CAs). We found (a) norepinephrine (NE), dopamine (DA), and epinephrine (E) concentrations from approximately 1.5 to 2.5, 3.5 to 4.5, and 6- to 10-fold higher, respectively, in suprapituitary than peripheral blood, (b) different NE/DA and NE/E ratios in favor of DA and E in suprapituitary blood, and (c), a complete (100%) group separation (suprapituitary vs. peripheral) when discriminant analysis included only DA and E. These data indicate that suprapituitary blood composition is different from that of the peripheral blood, and is particularly rich in CAs and claimed differences between DA and E release on one hand and NE release on the other in suprapituitary blood also are observed. We advance the hypothesis of a hypothalamic source of such amines draining via median eminence into portal vasculature, and name this blood "hypothalamic-hypophysial blood." Besides serving as "classical" neurotransmitters, CAs may also have a direct neurohormonal role in the regulation of the human hypothalamic-hypophysial function.
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Affiliation(s)
- R Paradisi
- Department of Obstetrics and Gynecology, S. Orsola Hospital, Bologna, Italy
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Lafond J, Bouvier C, Forget H, Lagace G, Kaufman S, Collu R. Regulation of Basal and stimulated prolactin release in prolactin-secreting rat pituitary tumors*. J Neuroendocrinol 1989; 1:9-14. [PMID: 19210476 DOI: 10.1111/j.1365-2826.1989.tb00070.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract To better understand the mechanisms of the inhibitory effects of dopamine on pituitary prolactin release, we have utilized an estrone-induced, benign and dopamine-sensitive rat pituitary adenoma and two malignant, transplantable and dopamine-resistant rat pituitary tumors, 7315a and MITW15. Enzymatically dispersed and Percoll purified cells obtained from the three tissues were incubated for 30 min in media with or without Na(+) and in the presence or the absence of dopamine and/or various prolactin releasers for evaluating the secretion of prolactin under baseline and experimental conditions. In some experiments, the cells were pretreated for 16 h with pertussis toxin to evaluate the eventual presence and role of pertussis toxin-sensitive G proteins. Dopamine inhibited baseline prolactin release by adenomatous lactotrophs in a Na(+)-dependent manner, but was totally inactive with 7315a and MtTW15 cells. The Ca(2+) channel agonist BAY K 8644 stimulated prolactin release with all three preparations and its effects were enhanced by a Na(+)-free medium. Dopamine antagonized the stimulatory effects of BAY K 8644 with adenomatous and 7315a cells only, even in the absence of Na(+). Pertussis toxin pretreatment significantly increased baseline prolactin release by adenomatous and MtTW15 cells and abolished dopamine inhibition of adenomatous lactotrophs baseline hormone release. BAY K 8644, TRH and vasoactive intestinal peptide, stimulated prolactin release by adenomatous cells and this effect was antagonized by dopamine in a pertussis toxin-sensitive manner. All prolactin releasers, except TRH, were effective also with 7315a cells, and its actions were not blocked by pertussin toxin. The stimulatory effects of BAY K 8644 and vasoactive intestinal peptide on 7315a cells were enhanced by pertussis toxin pretreatment. The results obtained with an almost pure preparation of adenomatous lactotrophs confirm the existence of a dual mechanism of dopamine inhibitory action on prolactin release: 1) a Na(+)-dependent action exerted on baseline, and 2) a Na(+)-independent action exerted on stimulated prolactin release. They also indicate that both actions are exerted through pertussis toxin-sensitive G proteins. Furthermore, our results show the presence in transplantable pituitary tumors 7315a and MtTW15 of multiple and diverse anomalies in the regulation of prolactin release probably due, at least partly, to anomalies of one or more G proteins and/or neurotransmitter receptors.
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Affiliation(s)
- J Lafond
- Research Unit on Reproductive and Developmental Biology, Pediatric Research Center, Hôpital Sainte-Justine and Université de Montreal, Montreal, Quebec H3T 1C5, Canada
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19
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Goldman JM, Cooper RL, Rehnberg GL, McElroy WK, Hein JF, Booth KC. Age-related changes in the regional distribution of hormones in the male rat anterior pituitary. Biochem Biophys Res Commun 1988; 152:1213-20. [PMID: 3132154 DOI: 10.1016/s0006-291x(88)80414-5] [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: 01/04/2023]
Abstract
Some heterogeneity in the localization of hormone-containing cells has been reported in the mammalian anterior pituitary. Since age-related changes are present in pituitary hormone concentrations, the present study was designed to explore if such changes in the male rat are regionally consistent. The results show clear geographic patterns in the presence of immunoreactive LH, FSH, prolactin and TSH. In the two year-old male, specific regional declines in hormone concentrations were present. With one regional exception, such was not the case when values were expressed in total hormonal content. A fall in gonadotropins still appeared in the medial area of the most caudal strip. The results suggest that with age, there is a displacement of hormone-containing cells in the pituitary and that for the gonadotropes this effect appears to be more prominent within the medio-caudal area.
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Affiliation(s)
- J M Goldman
- Northrop Services, Inc., Environmental Sciences, Research Triangle Park, N.C
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20
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Wang PS, Gonzalez HA, Porter JC. Saline ingestion stimulates the in situ molar activity of tyrosine hydroxylase in the median eminence and superior cervical ganglion. Brain Res 1988; 446:363-8. [PMID: 2897232 DOI: 10.1016/0006-8993(88)90895-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of drinking saline for 7 days on the mass and in situ activity of tyrosine hydroxylase (TH) in the median eminence (ME) and superior cervical ganglion (SCG) of rats were investigated. TH mass was quantified by immunoblot assay. In situ TH activity was calculated from the rate of intracellular accumulation of L-dihydroxyphenylalanine (DOPA). In rats that drank 10 mM, 30 mM, and 100 mM NaCl for 7 days, TH activity in the ME was 34 +/- 4, 36 +/- 5, and 45 +/- 3 (mean and S.E.M.) mol of DOPA.h-1.mol of TH-1, respectively, compared to 30 +/- 2 for rats that drank water. The activity of TH in the SCG of animals that drank 10 mM, 30 mM, and 100 mM NaCl was 143 +/- 24, 167 +/- 12, and 272 +/- 13 mol DOPA.h-1.mol TH-1, respectively, compared to 119 +/- 10 for animals that drank water. The mass of TH in the ME and SCG decreased as a function of the concentration of NaCl in the drinking water. In animals that drank water, 10 mM, 30 mM, and 100 mM NaCl, the amounts (pmol) of TH were, respectively, 0.28 +/- 0.03, 0.31 +/- 0.04, 0.23 +/- 0.02, and 0.21 +/- 0.01 per ME and 0.67 +/- 0.06, 0.72 +/- 0.11, 0.37 +/- 0.01, and 0.34 +/- 0.02 per SCG. TH activity in the ME or SCG was unaffected by treatment for 7 days with arginine vasopressin.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P S Wang
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Health Science Center, Department of Obstetrics and Gynecology, Dallas 75235
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Goldman JM, Cooper RL, Rehnberg GL, Booth KC, McElroy WK, Hein JF. Regional patterning of hormones in the female rat anterior pituitary: disproportionate changes over the estrous cycle. Endocr Res 1988; 14:263-82. [PMID: 3150751 DOI: 10.1080/07435808809032989] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The present study addressed the possibility that regional differences exist in the typical patterning of anterior pituitary hormones seen over the estrous cycle. The results show that LH in the rostral area of the pituitary, significantly higher than in other regions on diestrus, rises markedly on proestrus before falling late on that afternoon to concentrations comparable to other areas. Smaller cyclic changes were seen for lateral and caudo-central areas. The pattern of regional FSH concentrations on diestrus, while similar to LH, does not show the proestrus fall in the rostral region. Prolactin declines from a high on diestrus I to a low on late proestrus, but no regional disparities are present. TSH shows distinct regional differences and a fall in concentrations that coincides with the reported rise in serum estradiol. These findings indicate that the preovulatory surge of LH may represent a regionally disproportionate event, possibly involving inequalities in the relative amounts of gonadotropin-releasing hormone reaching various areas of the pituitary or differences in the ability of this releasing hormone to trigger LH release.
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Affiliation(s)
- J M Goldman
- Northrop Services, Inc., Environmental Sciences, Research Triangle Park, N.C
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22
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Mechanick JI, Cohen-Becker IR, Gregerson KA, Selmanoff M. Distribution of 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylglycol (DOPEG) in microdissected brain structures and the pituitary gland: metabolite changes in the median eminence in response to hyperprolactinemia and suckling. J Neural Transm (Vienna) 1987; 68:197-215. [PMID: 3559538 DOI: 10.1007/bf02098498] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Dopamine (DA), norepinephrine (NE), epinephrine (E), 3,4-dihydroxyphenylglycol (DOPEG) and dihydroxyphenylacetic acid (DOPAC) were determined simultaneously by a radioenzymatic, thin-layer chromatographic assay able to detect 1-10 pg of the parent compounds and 80-120 pg of their metabolites. A localization study of these compounds in 20 micro-dissected hypothalamic and limbic structures and the anterior and posterior pituitary glands of male rats was completed. DOPAC was detectable in 14 of 22 structures with the lowest DOPAC/DA ratio being found in the caudate nucleus (7.1%) and the highest in the medial aspect of the ventromedial nucleus of the hypothalamus (422.0%). There was a higher DOPAC/DA ratio in the lateral (21.5%) than in the medial (11.3%) portion of the median eminence suggesting that a greater portion of released DA in the medial median eminence enters the portal circulation. DOPEG was detectable in 6 of 22 structures with DOPEG/NE ratios ranging from 8% (interstitial nucleus of the stria terminalis, ventral aspect) to 32% (medial median eminence). A poor correlation exists between DOPAC and DA concentrations in the various brain regions while there was a stronger relationship between DOPEG and NE concentrations. Male rats were rendered hyper-prolactinemic for 48 hours with injections of ovine prolactin (oPRL) every 8 hours (4 mg/kg body weight sc). In such rats there was a suppression of endogenous rat PRL (rPRL) secretion, the DOPAC/DA ratio increased 2.2-fold in the medial (MEm) and 1.9-fold in the lateral median eminence (MEl), and the DA concentration in the anterior pituitary also increased 2.6-fold. In 10 day postpartum lactating rats, suckling produced marked increases in serum rPRL but no change in DOPAC/DA ratios in the ME or in the DA concentration in the anterior pituitary. The data reveal a wide range of DOPAC/DA ratios (7-422%) in brain regions containing cell bodies, axons and terminals of the different dopaminergic neuronal tracts in brain and pituitary. Considering the DOPAC/DA ratios in the MEm and MEl, it is suggested that a large perturbation of dopaminergic transmission produces a significant ratio change while a smaller perturbation is not detected by this index of neuronal metabolism.
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23
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Clarke IJ, Cummins JT. Pulsatility of reproductive hormones: physiological basis and clinical implications. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1987; 1:1-21. [PMID: 3297019 DOI: 10.1016/s0950-351x(87)80050-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The secretion of LHRH from the median eminence, into hypophyseal portal blood provides a signal whereby the central nervous system interfaces with the endocrine system. The pulsatile nature of this system originates from phasic neural signals and, except in extreme cases where pulses are eliminated by the pituitary action of steroids, pulse frequency is determined by LHRH secretion. Steroidal feedback and other extrinsic influences that affect pulse frequency act via neural afferents to the LHRH neurons. Amplitude regulation may be by way of steroidal influence at the level of the pituitary gland, or indirectly via changes in LHRH pulse frequency. In this chapter, we have attempted to outline our current knowledge of factors regulating LHRH pulsatility and how this is transmitted into pulsatile gonadotrophin secretion. Regarding PRL secretion, we have outlined evidence that pulsatility is inherent in the lactotrophs, requiring no hypothalamic input. The possible roles of PRL releasing factors in circumstances like suckling and stress and of PRL inhibiting factors have been discussed with reference to the pulsatile nature of PRL secretion.
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Collu R, Bouvier C. Effects of sulpiride and apomorphine on prolactin release in adrenalectomized animals. Role of sodium ions. Brain Res 1987; 401:23-9. [PMID: 2949800 DOI: 10.1016/0006-8993(87)91158-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The present experiments were performed to demonstrate in vivo the existence of a modulatory role of Na+ in the inhibitory control of prolactin (PRL) secretion. Groups of adult male rats were either adrenalectomized (adrenex) or sham-operated (normals) and implanted in the right atrium with a chronic cannula for the infusion of solutions or the sequential withdrawal of blood samples. Four days later, adrenex rats were infused for 1 h with either saline 0.9% or dextrose 5.6% (310 mOsm/kg H2O) at the rate of 10 ml/kg/h from Time -60 min until Time 0 min. All animals were injected at Time -45 min with sulpiride 0.05 mg/kg. At Time 0 min, some animals received apomorphine 5 mg/kg while others received a 0.05 mg/kg dose of the drug. Blood samples were obtained at -45, -30, -15, 0, 5, 10, 20 and 30 min for PRL assay. Plasma Na+ concentration was measured at -45, 0 and 30 min and plasma osmolarity at 0 min in adrenex rats. In normal controls plasma Na+ values were measured at the end of the experiment. Binding values (KD and Bmax) of pituitary D2-receptors were measured in adrenex and sham-operated rats using [3H]spiroperidol as ligand and D-butaclamol to define non-specific binding. Plasma Na+ values remained constant in saline-infused adrenex rats and similar to those of normal controls, while in dextrose-infused adrenex rats they fell progressively during the experimental period and were always lower than in the two other groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Selmanoff M, Walovitch RC, Walker GE, London ED. Effects of hyperprolactinemia on plasma prolactin and glucose and on local cerebral glucose utilization. J Neurochem 1987; 48:94-101. [PMID: 3491876 DOI: 10.1111/j.1471-4159.1987.tb13131.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Elevated blood levels of prolactin increase the synthesis, turnover, and release of 3,4-dihydroxyphenylethylamine (dopamine) from the tuberoinfundibular dopaminergic neurons, which project to the median eminence. The present study examined whether hyperprolactinemia also increases local cerebral glucose utilization, as determined by the 2-deoxy-D-[1-14C]glucose method, in the median eminence and other brain structures. Adult male rats were given ovine prolactin (4 mg/kg) subcutaneously every 8 h for 48 h. This treatment exerted an autoregulatory feedback effect on endogenous rat prolactin secretion, as evidenced by decreased circulating levels of rat prolactin. Ovine prolactin treatment also decreased plasma glucose concentrations. However, in both partially immobilized and free-ranging rats, glucose utilization in brain structures containing tuberoinfundibular dopaminergic cell bodies (the arcuate nucleus) and terminals (the median eminence) was not affected by ovine prolactin treatment. Hyperprolactinemia was, however, associated with decreased glucose utilization in the medial forebrain bundle and the CA subfield of the dorsal hippocampus. The lack of a significant effect of prolactin treatment on glucose utilization in the median eminence indicates that the resolution of the deoxyglucose technique, as used here, is not adequate to detect the ovine prolactin-induced increase in tuberoinfundibular dopaminergic neuronal activity, that the median eminence does not utilize glucose as its primary energy substrate, or that ovine prolactin treatment causes a counterbalancing decrease in the activity of other neurons projecting to the median eminence.
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26
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Gordon MN, Schechter JE, Felicio LS, Finch CE. Spontaneous tumors in aging female mice are more prevalent in the lateral pituitary zones. Neurobiol Aging 1987; 8:67-70. [PMID: 3561666 DOI: 10.1016/0197-4580(87)90060-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The localization of gross and microscopic spontaneous pituitary tumors was examined in aging female C57BL/6J mice. These tumors were lactotroph adenomas, by morphological and immunocytochemical criteria. Each lobe of the pars distalis was divided into three zones of approximately equal size and the number of tumors in each zone was counted. Twelve out of 30 tumors were located entirely within the most lateral zone. An additional 14 tumors occurred in both the most lateral and the interjacent zones. Thus, almost 90% of the observed tumors were localized in more lateral zones of the pars distalis (Chi-squared test, p less than 0.01). These findings support a hypothesis that lower portal blood dopamine levels reaching lateral portions of the pars distalis are a factor in the higher incidence of lactotroph adenomas in these zones.
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27
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Wang PS, Porter JC. Hormonal modulation of the quantity and in situ activity of tyrosine hydroxylase in neurites of the median eminence. Proc Natl Acad Sci U S A 1986; 83:9804-6. [PMID: 2879287 PMCID: PMC387230 DOI: 10.1073/pnas.83.24.9804] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The role of ovarian hormones in the control of the quantity and activity of tyrosine hydroxylase (TyrOHase) in neurites of the median eminence of the rat was investigated. TyrOHase was quantified by an immunoblot assay using purified rat TyrOHase as the standard. Treatment of ovariectomized animals with progesterone, but not estradiol, resulted in a significant reduction in the amount of TyrOHase in the median eminence. The in situ activity of the enzyme was assayed by measuring the rate of synthesis of L-3,4-dihydroxyphenylalanine (dopa), and the results were expressed as mol of dopa per hr per mol of TyrOHase. In animals treated with both estradiol and progesterone for 3 days, the in situ activity of TyrOHase in the median eminence was 114 +/- 13.5 (mean +/- SEM) compared to 26 +/- 4.7 for the controls. Estradiol or progesterone alone was much less effective than was the combination of estradiol and progesterone. To ascertain whether the effect of estradiol and progesterone on TyrOHase activity was reflected in the secretion of dopamine into hypophyseal portal blood, ovariectomized rats were treated for 3 days with both estradiol and progesterone or with the solvent vehicle. The concentration of dopamine in portal plasma of the hormone-treated animals was 1.93 +/- 0.533 ng/ml compared to 0.34 +/- 0.094 ng/ml in vehicle-treated animals. We conclude that the quantity and in situ molar activity of TyrOHase in neurites of the median eminence as well as the secretion of dopamine from these neurites are modulated by the combined action of estradiol and progesterone.
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Lafond J, Collu R. Effects of repeated stimuli on prolactin release in vitro from normal and adenomatous rat lactotrophs. Mol Cell Endocrinol 1986; 47:175-81. [PMID: 3091427 DOI: 10.1016/0303-7207(86)90029-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
It is now well known that dopamine (DA) plays a major role in the inhibitory control of prolactin (PRL); however, the mechanisms that are physiologically involved in the stimulation of PRL release are still under investigation. Indeed, although suppression of DA inhibitory tonus, administration of thyrotropin-releasing hormone (TRH) or vasoactive intestinal peptide (VIP) are all known PRL releasers, it is not clear whether they interact during physiological periods of PRL release such as suckling and estrus. No clear indications exist, furthermore, on whether they all act upon a same pituitary pool that may become depleted following repeated exposure to stimuli. Refractoriness to a single or a repeated stimulus has been reported to occur in prolactinoma-bearing or normal humans, respectively, the mechanism of which is still matter for discussion. Our present studies performed by perifusing normal or adenomatous rat lactotrophs attached to Cytodex I microcarrier beads was undertaken to try and answer some of these questions. The experimental period consisted in perifusing the cells for 1 h with Dulbecco's modified Eagle's medium (DMEM) containing DA 10(-5) M, then for 2 h with either DMEM, DMEM and TRH 10(-8) M, DMEM and VIP 10(-7) M, then again with DA in DMEM for 1 h, and finally with DMEM, DMEM and TRH, or DMEM and VIP. Three experiments of various combinations were performed. Lower PRL levels were observed under DA, while two periods (first and second) of PRL release followed the suppression of DA infusion with or without the addition of either one of the two peptides.(ABSTRACT TRUNCATED AT 250 WORDS)
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Lafond J, Ducharme JR, Collu R. Inhibition of prolactin release and blockade of adenohypophyseal cell cyclic AMP accumulation are two dissociable effects of dopaminergic and non-dopaminergic drugs. Mol Cell Endocrinol 1986; 44:219-25. [PMID: 3007237 DOI: 10.1016/0303-7207(86)90127-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The secretion of PRL by the anterior pituitary gland is under a tonic inhibitory control exerted by dopamine (DA). However, the mechanism(s) involved in the inhibition of PRL secretion is not clearly defined. Several recently published papers supported the hypothesis that DA inhibits the release of PRL through blockade of the pituitary adenylate cyclase-cyclic AMP system. We have recently demonstrated that sodium ions are essential for dopaminergic inhibitory action on PRL secretion. The present paper reports the effects, in the presence or in the absence of Na+, of either DA, bromocriptine, apomorphine or 2 anticalmodulin drugs, penfluridol and W-7, on cyclic AMP accumulation by rat adenohypophyseal cells in primary culture. Studies with dopaminergic agonists show that in the presence of Na+ inhibition of both PRL and cyclic AMP is obtained at 15 and 30 min, while in the absence of the ion a dissociation exists between the inhibition of PRL release which is completely abolished, and that of cyclic AMP content which is still present. Dose-response studies done in the presence of Na+ show the existence of a good correlation between hormone and nucleotide effects of dopaminergic agonists while, in the absence of Na+, a dissociation is observed between the inhibition of PRL release, which is completely suppressed, and that of cyclic AMP accumulation which is slightly or not at all decreased. The inhibitory effects of penfluridol after 15 and 30 min of incubation were not suppressed by Na+ removal, although its hormonal actions were slightly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)
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Ghigo E, Goffi S, Molinatti GM, Camanni F, Massara F. Prolactin and TSH responses to both domperidone and TRH in normal and hyperprolactinaemic women after dopamine synthesis blockade. Clin Endocrinol (Oxf) 1985; 23:155-60. [PMID: 3931942 DOI: 10.1111/j.1365-2265.1985.tb00210.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A study of the effect of alpha-methyl-1-tryosine (metyrosine) blockade (2 g/d for 2 d) of dopamine (DA) synthesis on the PRL and TSH response to domperidone (DOM) and TRH in normal women and subjects with pathological hyperprolactinaemia is reported. In the normal subjects, there was a marked increase in basal PRL (51.7 +/- 11.1 vs 5.7 +/- 1.0 ng/ml) and the PRL and TSH responses to DOM were abolished. The PRL response to TRH was also reduced. In the hyperprolactinaemic subjects, metyrosine had no effect on basal PRL nor on the virtually non-existent PRL response to DOM, whereas it abolished the exaggerated TSH response. The conclusion is drawn that the response of both PRL and TSH to DA receptor blockers is really dependent upon DA inhibitory tone. A fall in this tone can also be postulated as responsible for the hyporesponsiveness of PRL to DOM frequently observed in pathological hyperprolactinaemia. In addition, the fact that metyrosine also abolished the exaggerated TSH response to DOM shows that the latter is totally dependent on enhanced DA inhibition of the thyrotrophs. Lastly, the reduced PRL response to TRH after metyrosine indicates that DA partly determines the ability of the lactotrophs to respond to TRH.
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Sheaves R, Warburton E, Laynes R, Mackinnon P. Adrenaline concentration and turnover in the arcuate nucleus and median eminence during the critical period in the rat. Brain Res 1984; 323:326-9. [PMID: 6525520 DOI: 10.1016/0006-8993(84)90307-x] [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: 01/20/2023]
Abstract
Previous work has shown a relatively high turnover of adrenaline in the mediobasal hypothalamus during the critical period (15.00-17.00 h) of the proestrous rat. We now report that this high level of adrenergic activity can be detected in the median eminence (turnover rate 1.62 +/- 0.36 pg/micrograms protein/h) rather than the arcuate nucleus (turnover rate 0.18 +/- 0.32 pg/micrograms protein/h). In addition the median eminence was isolated as medial and lateral components and determination of catecholamine concentrations revealed a greater proportion of adrenaline (A) (59%) in the lateral median eminence whereas a larger proportion of dopamine (60%) was found in medial median eminence.
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32
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Porter JC, Reymond MJ, Arita J, Sissom JF. Secretion of hypothalamic dopamine into the hypophysial portal vasculature: an overview. Methods Enzymol 1983; 103:607-18. [PMID: 6142401 DOI: 10.1016/s0076-6879(83)03043-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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