Abstract:
UNLABELLED:Opioid peptides are present in both the posterior pituitary (PP) and stalk-median eminence (SME). Their effects on the dopaminergic neurons in the SME are well documented, but little is known concerning their role in the regulation of dopamine (DA) release from the PP. The objectives of this study were (1) to develop an in vitro method suitable for examining the regulation of endogenous DA release from PP and SME, and (2) to describe and compare the effects of selected opioid peptides on potassium-evoked DA release from these tissues. Tissues were dissected from ovariectomized rats and incubated in media. After equilibration, two pulses of 28 mM potassium (K+), 3 min each, were delivered 30 min apart. Test substances were administered 20 min before the second K+ stimulus. DA in the media was determined by high-performance liquid chromatography. Potassium at 28 and 56 mM elicited a marked increase in DA release from the PP and SME; this was abolished by the removal of calcium. The opioid receptor antagonist, naloxone, significantly increased the release of DA from both PP and SME by 55%. Dynorphin A elicited a significant inhibition of DA release from PP and SME by 33 and 50%, respectively. In contrast, methionine enkephalinamide decreased DA release from the SME by 50%, but was without effect in the PP. The release of DA from both PP and SME was significantly inhibited by beta-endorphin, and this was reversed by naloxone. However, beta-endorphin was fourfold more effective in the SME. N-acetyl-beta-endorphin did not alter DA release. CONCLUSIONS:(1) we have developed a simple and sensitive in vitro method for studying the effects of hormones and drugs on the release of endogenous DA from PP and SME; (2) tuberoinfundibular dopaminergic and tuberohypophyseal dopaminergic nerve terminals are subjected to a similar inhibitory control by endogenous opioid peptides, and (3) exogenously applied opioid peptides exert differential effects on the release of DA from SME and PP which could be attributable to a dissimilar distribution of opioid receptor subtypes in these two tissues.
journal_name
Neuroendocrinologyjournal_title
Neuroendocrinologyauthors
Garris PA,Ben-Jonathan Ndoi
10.1159/000125612subject
Has Abstractpub_date
1990-10-01 00:00:00pages
399-404issue
4eissn
0028-3835issn
1423-0194journal_volume
52pub_type
杂志文章abstract::We used an in vivo pharmacological approach to investigate the potential influence of serotonin (5-HT) on peptide release from the intermediate lobe (IL) of the rat pituitary. Plasma levels of alpha-melanocyte-stimulating hormone (alpha-MSH) as well as the ultrastructural appearance of IL cells were used as indicators...
journal_title:Neuroendocrinology
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更新日期:1983-06-01 00:00:00
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doi:10.1159/000123288
更新日期:1982-02-01 00:00:00
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doi:10.1159/000123225
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更新日期:1993-12-01 00:00:00
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journal_title:Neuroendocrinology
pub_type: 杂志文章
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更新日期:1978-01-01 00:00:00
abstract::Previous work has demonstrated that physiological concentrations of 17beta-estradiol can protect the female rat brain against middle cerebral artery occlusion (MCAO)-induced ischemic damage. The present study examined whether therapeutic doses of the clinically relevant selective estrogen receptor modulator (SERM), ta...
journal_title:Neuroendocrinology
pub_type: 杂志文章
doi:10.1159/000068332
更新日期:2003-01-01 00:00:00
abstract::The influence of the hypothalamus on the development of the anterior pituitary cells was studied in normal and anencaphalic human fetuses. An immunocytological method was applied to study the quantitative evolution of the size of the cells during gestation. The somatotropic and corticotropic cells appeared at the end ...
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pub_type: 杂志文章
doi:10.1159/000122709
更新日期:1977-01-01 00:00:00
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journal_title:Neuroendocrinology
pub_type: 杂志文章
doi:10.1159/000126605
更新日期:1993-12-01 00:00:00
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pub_type: 杂志文章
doi:10.1159/000124463
更新日期:1986-01-01 00:00:00
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pub_type: 杂志文章
doi:10.1159/000124638
更新日期:1986-01-01 00:00:00
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journal_title:Neuroendocrinology
pub_type: 杂志文章
doi:10.1159/000124844
更新日期:1987-10-01 00:00:00
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更新日期:1993-05-01 00:00:00
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更新日期:1983-07-01 00:00:00
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更新日期:1996-04-01 00:00:00
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更新日期:1985-08-01 00:00:00
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更新日期:1997-02-01 00:00:00
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更新日期:2009-01-01 00:00:00
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journal_title:Neuroendocrinology
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更新日期:1981-04-01 00:00:00
abstract::Corticotropin-releasing hormone (CRH) plays a key role in adjusting the basal and stress-activated hypothalamic-pituitary-adrenal axis (HPA). CRH is also widely distributed in extrahypothalamic circuits, where it acts as a neuroregulator to integrate the complex neuroendocrine, autonomic, and behavioral adaptive respo...
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pub_type: 杂志文章,评审
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更新日期:2011-01-01 00:00:00
abstract::In situ hybridization was used to examine the effects of amygdala kindling on the expression of mRNAs for mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) in the rat hippocampus. Kindling increased MR mRNA levels in the dentate gyrus of the hippocampus 4 h after the last seizure, and these levels rem...
journal_title:Neuroendocrinology
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doi:10.1159/000126691
更新日期:1994-05-01 00:00:00
abstract::The involvement of histaminergic transmission in the rapid and sustained plasma ACTH and corticosterone (CORT) responses induced in conscious rats by intra-arterial infusions of 25 micrograms.kg-1 Escherichia coli lipopolysaccharide (LPS) was investigated. LPS challenge produced a rapid and transient increase (+ 62%) ...
journal_title:Neuroendocrinology
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更新日期:1996-03-01 00:00:00
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journal_title:Neuroendocrinology
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更新日期:1996-08-01 00:00:00
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pub_type: 杂志文章
doi:10.1159/000507761
更新日期:2020-04-08 00:00:00
abstract::Gastroenteropancreatic (GEP) endocrine tumors are hypervascular tumors able to synthesize and secrete high amounts of VEGF. We aimed to study the regulation of VEGF production in GEP endocrine tumors and to test whether some of the drugs currently used in their treatment, such as somatostatin analogues and mTOR inhibi...
journal_title:Neuroendocrinology
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更新日期:2010-01-01 00:00:00