摘要:

Glucocorticoids (GCs) can damage the hippocampus when exposure is prolonged, as well as impair the capacity of hippocampal neurons to survive various neurological insults. We have recently demonstrated that GCs impair the capacity of primary hippocampal cultures to survive many of these same insults. Using this culture system, we have characterized the features with which the GC corticosterone (CORT) impairs the capacity of these cells to survive the excitotoxin kainic acid. The GC endangerment seems to be mediated by the type II, but not type I corticosteroid receptor. As evidence for type II involvement, endangerment of cells was caused by CORT concentrations in the kilodalton range for the type II receptor, and also by the type II ligand dexamethasone; moreover, the endangerment was blocked by a type II antagonist. In contrast, a type I antagonist was not protective. Cultures contained both type I and II receptors. The effect was GC-specific, as cultures were endangered by CORT, cortisol and dexamethasone, but not by non-GC steroids. GCs did not exacerbate kainic acid damage in cerebeller or hypothalamic cultures, despite the presence of corticosteroid receptors. This agrees with the in vivo data showing that the GC exacerbation of neurological insults is either exclusive to or predominant in the hippocampus.

ISSN:0028-3835    

DOI:10.1159/000125400

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

We have localized and characterized the binding of the melatonin agonist, 2-[125I]iodomelatonin, in the rat area postrema (AP), by using quantitative autoradiography in vitro. At equilibrium conditions, Scatchard analysis revealed saturable high-affinity binding to a single class of sites (Ka 45.9 ± (SE) 6.0 pM and Bmax 30.8 ± 4.6 fmol/mg protein, n = 4 experiments with a total of 18 rats). Melatonin and 6-hydroxymelatonin were potent displacers of 2-[125I]iodomelatonin binding in the AP (IC50 20 and 500 pM, respectively) while N-acetylserotonin exhibited only a modest potency (IC50 25 nM). Micromolar concentrations of guanine nucleotides dose-dependently and specifically inhibited agonist binding at 22 ° C. Saturation studies revealed that this was due to a decrease in binding affinity. Divalent cations (4 mM CaCl2 or 2 mM MgCl2) had no detectable effect on the affinity of the binding site, whereas physiological concentrations of NaCl significantly decreased the binding affinity. These results demonstrate specific high-affinity binding sites for 2-[125I]iodomelatonin in the rat AP and suggest coupling of these putative receptors to guanosine nucleotide binding regulatory protein(

ISSN:0028-3835    

DOI:10.1159/000125401

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The Nb2 rat lymphoma cell prolactin (PRL) bioassay was used, in conjunction with standard radioimmunoassay techniques, to examine the effects of various stressors on plasma bioactive (bio) and immunoreactive (ir) PRL levels in 3- to 5- and 22- to 24-month-old male Copenhagen-Fischer 344 rats. The animals were implanted with chronic intracardiac venous cannulas 24–48 h prior to experimentation. Serial blood samples were taken prior to, during and after exposure to either 15 min restraint stress, 15 min strobe light stress or 2 min ether stress. In 2 of 3 studies, basal prestress irPRL levels were significantly higher in old as compared to young male rats. However, in all studies, basal bioPRL levels were significantly lower in the older animals. Exposure to restraint, strobe light or ether stress induced significant and parallel increases in plasma ir- and bioPRL levels in young rats, and these stressors did not affect the ratio of blood bio/irPRL. Old rats exposed to the same stressors displayed similar increases in plasma irPRL, but bioPRL release was significantly attenuated and the ratio of plasma bio/irPRL levels was significantly lower when compared to young rats. In contrast, ether stress induced similar increases in plasma ir- and bioPRL levels in both age groups and restored the ratio of plasma bio/irPRL levels in old rats to that of young animals. These results demonstrate that, despite having significantly higher basal plasma irPRL levels, the bioactivity of this hormone is significantly diminished in old as compared to young male rats. These results also demonstrate that, although various stressors induce similar increases in irPRL, they have differential effects on the circulating levels of bioPRL in young and old rats. These findings suggest that during the aging process qualitative changes occur in PRL biosynthesis, processing and/or release, which significantly reduces the biopotency of this hormone when secreted during basal conditions and in response to certain types of stres

ISSN:0028-3835    

DOI:10.1159/000125402

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Amantadine, a well-known antiviral agent, causing an increase in dopamine synthesis, release and the inhibition of re-uptake of noradrenaline and dopamine in central and peripheral catecholaminergic neurons, is successfully used in the treatment of Parkinson’s disease. In the present paper, we have studied the effect of various doses of amantadine on in vivo prolactin secretion and the incorporation of 3H-thymidine and 3H-spiperone binding by the anterior pituitary gland of long-term diethylstil-boestrol-treated male Wistar rats. Four weeks after a subcutaneous implantation of Silastic tubes containing 10 mg of diethylstil-boestrol, a dramatic rise in serum prolactin levels was observed, accompanied by an increased uptake of 3H-thymidine by DNA anterior pituitary cells. Amantadine, given in the subcutaneous doses of 50, 5 and 0.5 mg/kg of body weight attenuated the stimulatory effect of stilboestrol on serum prolactin concentration in a dose-dependent fashion. On the other hand, the incorporation of 3H-thymidine into DNA pituitary cells in all the groups of amantadine-treated rats was only slightly suppressed. In an additional experiment, Scatchard analyses were performed on the in vitro 3H-spiperone binding kinetics in a dispersed anterior pituitary cell culture prepared from the pituitaries of 6-week diethylstilboestrol-treated rats. It has been found that amantadine injected in the dose of 5 mg/kg of body weight for 14 days induced a twofold decrease in the density of dopamine D2 binding sites (36.6 ± 9.4 vs. 70.3 ± 3.4 fmol/l06 cells; p < 0.02), while the apparent affinity of the receptors was unchanged. It is concluded then that the inhibitory effect of amantadine on pituitary prolactin cell function seems to be related to the modulation of synthesis and release of dopamine from hypothalamic dopaminergic neurons and to the down-regulation of dopaminergic D2 binding sites within the anterior pituitary gl

ISSN:0028-3835    

DOI:10.1159/000125403

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

To assess the chronic effects of interleukin-1 (IL-1) and IL-2 on the hypothalamo-pituitary-adrenal axis in vivo, we administered recombinant human (rh) IL-1α, rhIL-1β or rhIL-2 (2.0 µg/day) repetitively to adult male rats for 10 days. In rhlL-1β-treated rats, adrenocorticotropic hormone-like immunoreactivity (ACTH-LI) of the anterior pituitary appeared to increase first on day 3 followed by an increase of corticotropin-releasing hormone (CRH)-LI both in the hypothalamus and in the adrenal gland after day 7. At the end of the 10-day treatment, wet weights of the adrenal glands of rhIL-1β-treated rats increased significantly compared with those of control rats. Plasma ACTH levels in rhIL-1 β-treated rats at the sampling time continued to be elevated throughout the experimental period. Under the same experimental design, rhIL-1α increased plasma ACTH levels at the sampling time without changes in adrenal weight or in the peptide contents investigated. The same amount of rhIL-2 had no effect on these measured variables during the 10-day treatment. These data indicate that the repetitive administration of IL-1β resulted in chronic effects in the hypothalamo pituitary-adrenal axis to increase the activities in these organs during the treatment and, moreover, IL-1 possibly has a positive direct effect on the CRH-containing cells in the adrenal

ISSN:0028-3835    

DOI:10.1159/000125404

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

We determined the effect of 17β-estradiol (E2) on synthesis and release of luteinizing hormone (LH) induced by drugs which activate intracellular signal transduction mechanisms in rat anterior pituitary cells. Cells were pretreated with E2 (6 × 10–10M) or diluent for 24 h, then washed and incubated for 4 h with E2 or diluent, respectively, in the presence or absence of drugs. LH translation and glycosylation were monitored by measuring incorporation of [14C]alanine and [3H]glucosamine, respectively, into total (medium plus cells) immunoprecipitable LH. Immunoreactive LH (IRLH) was measured by radioimmunoassay. Gonadotropin-releasing hormone (GnRH, 1 ILM), veratridine (5 µM), L-α-1,2-dioctanoyl glycerol (C8, 200 µM), and phospholipase C (PLC, 0.24 U/ml) all increased (p < 0.01) medium IRLH, [3H]glucosamine-LH, and [14C]alanine-LH, and total [3H]glucosamine-LH in both E2- and diluent-treated cells. Total IRLH or [14C]alanine-LH were not increased by any treatment. E2 alone slightly increased (p < 0.05) basal medium IRLH and [3H]glucosamine-LH. The stimulatory effects of E2 on basal medium [14C]alanine-LH and total [3H]glucosamine-LH were inconsistent. E2 potentiated (p < 0.01) the effects of veratridine, C8, PLC, and GnRH on medium IRLH, and medium and total [3H]glucosamine-LH. E2 also potentiated (p < 0.01) the effects of veratridine, PLC, and GnRH, but not of C8, on medium [14C]alanine-LH. In contrast, E2 did not increase either precursor uptake or incorporation of precursor into total protein in the presence of any secretagogue. These results suggest that LH glycosylation, like LH release, may involve the Ca2+ and PLC pathways, and that E2 augments LH glycosylation and release by interacting with these pa

ISSN:0028-3835    

DOI:10.1159/000125405

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Vasoactive intestinal peptide (VIP) inhibits pulsatile luteinizing hormone (LH) secretion in the ovariectomized rat. Hypothalamic nuclei known to contain VIPergic neurons were destroyed electrolytically to determine whether either an increased response or a loss of response to exogenous VIP would result. Bilateral electrolytic lesions were made of either the suprachiasmatic (SCN) or paraventricular (PVN) nuclei in separate experiments; all animals received an intracerebroventricular cannula at the same time. Sham-lesioned animals were used as a control. One week later, a catheter was placed in the jugular vein of each rat and, after a recovery period of at least 2 h, blood samples were taken every 5 min for 3 h. After a control period of 1.5 h, either VIP or saline was infused into the third ventricle for an additional 1.5 h. Two doses of VIP were used: 3.5 nmol/h, previously shown to be inhibitory, and 0.4 nmol/h, which is ineffective in ovariectomized rats. LH was measured in the plasma by radioimmunoassay. The high dose of VIP lowered mean LH levels and pulse frequency but had no effect on pulse amplitude in both sham-lesioned and SCN-lesioned rats. The low dose of VIP did not affect pulsatile LH patterns in sham-lesioned rats, but did lower mean LH and pulse frequency in SCN-lesioned rats, indicating a denervation hypersensitivity subsequent to SCN lesions. Destruction of the PVN abolished the inhibitory effect of the high dose of VIP on pulsatile LH release. The low dose of VIP was ineffective in both PVN- and sham-lesioned animals. We interpret these results to mean that exogenous VIP inhibits pulsatile LH secretion in the ovariectomized rat through an effect on the terminal fields in the PVN of VIPergic neurons whose cell bodies are in the SCN, and that this effect is mediated by a non-VIPergic connection between the PVN and the gonadotropin-releasing hormone pulse generator.

ISSN:0028-3835    

DOI:10.1159/000125406

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The treatment of GH4C1 cells, a prolactin-producing rat anterior pituitary cell line, with estradiol (1 nM), insulin (300 nM) and epidermal growth factor (10 nM) has been previously shown to substantially increase both the intracellular level of prolactin, as well as the number of secretory granules. In this study, we examined the effect of this treatment on levels of carboxypeptidase E (CPE), a prohormone-processing enzyme. GH4C1 cells contain CPE mRNA and enzymatic activity. The secretion of both prolactin and CPE activity from GH4C1 cells is stimulated 10-fold by 50 ml KCl and 2- to 3-fold by 100 nM thyrotropin-releasing hormone, suggesting that these two proteins are contained in secretory granules. Treatment of GH4C1 cells with estradiol, insulin, and epidermal growth factor causes an increase in the intracellular level of CPE to approximately 2-fold of control values. This change is much smaller than the change in the level of prolactin: intracellular prolactin is increased 140-fold by the treatment. Kinetic analysis of the CPE activity indicates that the treatment does not alter the Km of substrate hydrolysis, with the change in activity the result of an increase in apparent Vmax. Northern blot analysis indicates that the level of CPE mRNA is not influenced (<10%) by the treatment, whereas the level of prolactin mRNA is increased 9-fold. These results indicate that CPE is not coordinately regulated with prolactin in the GH4C1 cell line, although some regulation of CPE activity does occur.

ISSN:0028-3835    

DOI:10.1159/000125407

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Incubation of cultured goldfish pituitary cells with 10 nM to 1 µM apomorphine (APO), a non-selective dopamine agonist, increased growth hormone (GH) release in a dose-dependent manner. GH release was also stimulated in a dose-dependent manner by 0.1 nM to 1 µM salmon gonadotropin (GTH)-releasing hormone (sGnRH), sGnRH analog, and chicken GnRH-II (cGnRH-II). The magnitude of GH responses to 1 µM GnRHs were less than that to 1 µM APO. GH responses to 10 nM to 1 µM APO were not significantly increased by the addition of GnRHs. Static incubations with 0.1 nM to 1 µM of the dopamine Dl agonist SKF38393 did not alter basal GTH release, or the GTH responses to 10 nM sGnRH and cGnRH-II. In contrast, the Dl agonist SKF38393 significantly increased basal GH secretion with maximal stimulation achieved at 100 nM concentration, and GH responses to 10 nM sGnRH and 10 nM cGnRH-II were enhanced by simultaneous applications of SKF38393. Incubation with 1 µM of the D2 agonist LY171555 decreased basal GTH release. Additions of 0.1 nM to 1 µM LY171555 caused dose-dependent decreases in the GTH secretion induced by 10 nM sGnRH and cGnRH-II. In contrast, basal and GnRH-stimulated GH release were not affected by coincubations with LY171555. The Dl antagonist SKF83566 and the D2 antagonist domperidone, at 1 µM concentrations, specifically blocked the Dl agonist SKF38393-stimulated increase in GH release and the D2 agonist LY171555-induced depression of GTH secretion, respectively. In cell column perifusion studies, the Dl agonist SKF38393 at 0.1 nM to 1 µM had no effects on GTH release, but significantly elevated GH secretion rates when applied at 0.1–1 µM concentrations. The GH release induced by 1 µM SKF38393 was significantly reduced by simultaneous perifusion with 1 µM of the Dl antagonist SKF83566. Treatments with SKF38393 and/or SKF83566 did not affect net GTH and GH responses to sGnRH challenges. In contrast, perifusion with 0.1 and 1 µM of the D2 agonist LY171555 depressed basal as well as sGnRH-induced GTH responses. These effects of 1 µM LY171555 were completely blocked by simultaneous applications of 1 µM domperidone, a D2 antagonist. Treatments with these D2 selective drugs did not affect basal and sGnRH-stimulated GH release. These results indicate that in cultured goldfish pituitary cells, activation of dopamine Dl- and D2-like receptors specifically stimulates GH release and inhibits both basal and stimulated GTH secretion, respectively. The presence of direct actions of sGnRH and cGnRH-II on goldfish GTH an GH release are also demonstrated. This is the first study do demonstrate stimulatory dopamine Dl actions in the ver

ISSN:0028-3835    

DOI:10.1159/000125408

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The present studies were designed to evaluate the role of substance P (SP) in the control of the release of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL). SP was microinjected into the medial preoptic area (MPOA) of conscious, freely moving intact or orchidectomized (ORCX; 21 days post-ORCX) adult male rats. Microinjection of SP into the MPOA induced a significant decrease in plasma LH and FSH concentrations, effects which were accompanied by an elevation in plasma PRL concentration. To examine the participation of endogenously secreted SP in the activity of the MPOA neurons controlling release of these cited pituitary hormones, another study was performed in which either a potent and specific antagonist to SP (D-Pro2,D-Trip7,9-SP; SP-ANT) or an antibody against SP (SP-AB), was injected into the MPOA. SP-ANTand SP-AB both elevated plasma LH, FSH and decreased plasma PRL concentration. These data suggest that endogenous SP within the MPOA exerts an important inhibitory tonus over LH and FSH release and an excitatory tonus over PRL release. In conclusion, SP seems to participate as a neurotransmitter or neuromodulater in the control of LH, FSH and PRL secretion, at least in part, by acting at the level of MPOA, a region in which the neuronal cell bodies that produce LH-releasing hormone and the associated gonadotropin-releasing hormone-associated peptide are located.

ISSN:0028-3835    

DOI:10.1159/000125409

出版商:S. Karger AG    

年代:1990

数据来源: Karger