bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increased Expression of Type 1 Angiotensin II Receptors in the Hypothalamic Paraventricular Nucleus following Stress and Glucocorticoid Administration
Authors: Aguilera Greti , Kiss Alexander , Luo Xun 
Published: September 2006

AbstractDouble staining in situ hybridization studies have shown that angiotensin II (All) type 1 receptors (AT1) in the hypothalamic paraventricular nucleus (PVN) are located primarily in corticotropin releasing hormone (CRH) neurons of the parvicellular subdivision. The purpose of these studies was to investigate the role of All regulating the hypothalamic‐pituitary adrenal (HPA) axis, by correlating AT1 receptor expression levels in the PVN with the known changes in activity of the HPA axis under different stress paradigms, and manipulation of circulating glucocorticoids. AT1 receptor mRNA was measured by in situ hybridization using 35S‐labelled cRNA probes and All binding by autoradiography using 125I[Sar1,lle8]All in slide mounted hypothalamic sections. AT1 receptor mRNA levels and All binding in the PVN were reduced by about 20% 18 h after adrenalectomy remaining at these levels up to 6 days after. This effect was prevented by corticosterone administration in the drinking water, or dexamethasone injection (100 mg, s.c., daily). Conversely, dexamethasone injection in intact rats caused a 20% increase in AT1 receptor mRNA in the PVN. AT1 receptor mRNA and binding in the PVN increased 4 h after exposure to stress paradigms associated with activation of the HPA axis (immobilization for 1 h, or i.p. injection of 1.5 M NaCl), and remained elevated after repeated daily stress for 14 days. Unexpectedly, two osmotic stress models associated with inhibition of the HPA axis (60 h water deprivation or 12 days of 2% saline intake) also resulted in increased AT1 receptor mRNA levels and All binding in the parvicellular PVN. In intact rats, the stimulatory effect of acute stress on AT1 receptor mRNA in the PVN was significantly enhanced by dexamethasone administration (100 μg, s.c., 14 h and 1 h prior to stress), while in adrenalectomized rats, with or without glucocorticoid replacement, stress reduced rather than increased, AT1 receptor mRNA. Dexamethasone, 100 μg, injected sc within 1 min the beginning of immobilization in adrenalectomized rats, increased AT1 receptor mRNA in the PVN to levels significantly higher than those after dexamethasone alone, indicating that the stress induced glucocorticoid surge is required for the stimulatory effect of stress on AT1 receptor mRNA. The data suggest that AT1 receptor expression in the PVN is under dual control during stress: stress‐activated inhibitory pathways and the stimulatory effect of glucocorticoids. The lack of specificity of the changes in AT1 receptor expression in the PVN following stressors with opposite effects on ACTH secretion (osmotic and physical‐psychological stress) does not support a role for All as a major determinant of the response of the HPA axis during stress.
Bacterial Lipopolysaccharide‐Induced Changes in FOS Protein Expression in the Rat Brain: Correlation with Thermoregulatory Changes and Plasma Corticosterone
Authors: Hare A. S. , Clarke G. , Tolchard S. 
Published: September 2006

AbstractIn the present study the regions of the brain showing an increase in the number of FOS protein stained cells 180 min following intravenous saline or bacterial lipopolysaccharide (LPS) treatment were investigated and correlated with changes in body temperature and plasma corticosterone levels. Particular attention was given to the possible involvement of the circumventricular organs and regions of the brainstem containing central noradrenergic neurones. LPS at doses of 0.35, 3.5 and 50 μg caused highly significant increases in FOS protein expression in the organum vasculosum of lamina terminalis, the area postrema and the subfornical organ compared with saline controls. Marked increases in bacterial lipopolysaccharide‐induced FOS protein expression were observed in the ventrolateral medulla, the nucleus of the solitary tract and the locus coeruleus which contain the A1, A2 and A6 noradrenergic neurones respectively. The changes in body temperature induced by LPS were found to be dependent upon the dose of LPS administered; the lowest dose employed (0.35 μg) induced an immediate and sustained fever, 3.5 μg LPS caused a biphasic response consisting of a hypothermic response followed by a febrile response, whereas 50 μg LPS induced a hypothermic response which then normalised by 160 min post‐injection. Intravenous saline injection had no significant effect on body temperature. The occurance of LPS‐induced hypothermia was coincident with increased FOS expression in the bed nucleus of stria terminalis, which houses vasopressinergic neurones involved in antipyresis, whereas in animals showing an LPS‐induced febrile response there was no significant difference in the number of FOS stained cells in the bed nucleus of stria terminalis compared with saline treated animals. LPS also caused marked increases in FOS protein expression in the parvocellular regions of the paraventricular nucleus (pPVN) of the hypothalamus, the central nucleus of the amygdala and the ventral septa1 area. Plasma corticosterone was unaffected by the lowest dose of LPS (0.35 μg), however the higher doses employed (3.5 and 50 μg) caused significant increases in plasma corticosterone which correlated with the increases in the number of FOS stained cells in the pPVN. The results of the present study suggest that, in addition to the organum vasculosum of lamina terminalis, the area postrema and subfornical organ may be important in the responses to antigenic challenge that are mediated by the central nervous system. They also add support to the possible involvement of the bed nucleus of stria terminalis in LPS‐induced hypothermia and of the involvement of the of the major noradrenergic cell groups (A1, A2 & A6) and a number of hypothalamic and extrahypothalamic forebrain regions in the interaction of immune and central nervous systems.
Effects of Dopamine D1 and D2 Receptor Agonists and Antagonists on Basal and Ethanol‐Modulated β‐Endorphin Secretion from Hypothalamic Neurons in Primary Cultures
Authors: Boyadjieva Nadka. I. , Sarkar Dipak. K. 
Published: September 2006

AbstractIn the present study, we determined the effects of dopamine receptor agonists and antagonists on basal and ethanol‐modulated β‐endorphin (β‐EP) secretion from hypothalamic neurons in primary cultures. Treatment with various concentrations of dopamine D1 agonist SKF 38393 and D1 antagonist SCH 23390 did not affect basal IR‐β‐EP release. However, dopamine D2 receptor agonist LY 141865 reduced basal immunoreactive (IR)‐β‐EP release in a concentration dependent manner. D2 receptor antagonist, sulpiride, on the other hand, stimulated basal IR‐β‐EP release and blocked LY 141865‐induced inhibition of IR‐β‐EP release in a concentration dependent manner. When the actions of these DA receptor agents on ethanol‐modulated IR‐β‐EP release were studied, both D1 and D2 receptor agents failed to affect ethanol‐modulated IR‐β‐EP release. These data suggest that the endogenous secretion of β‐EP from hypothalamic neurons is under the influence of an inhibitory dopaminergic system involving the D2 receptor. Furthermore, ethanol's effects on β‐EP secretion are not mediated by dopamine.
Cyclosporin A and FK506 are Potent Activators of Proopiomelanocortin‐Derived Peptide Secretion Without Affecting Corticotrope Glucocorticoid Receptor Function
Authors: Sheppard Karen E. 
Published: September 2006

AbstractUnliganded glucocorticoid receptors (GR) are localized in the cytoplasm and are associated with heat shock protein (hsp)90, hsp70, and a member of the immunophilin family, FK506 binding protein 59 (FKBP59). Several members of the cyclophilin and FKBP families have now been shown to associate with unactivated steroid receptors, however the physiological role these immunophilins play in steroid receptor function is questionable. In the present study we have measured GR binding and nuclear translocation of activated receptor in corticotrope cells following treatment with the immunophilin ligands FK506 and cyclosporin A (CsA). Extensive GR binding studies in AtT20 cells, a mouse corticotrope tumor cell line failed to demonstrate an effect of FK506 or CsA on either the ability of GR to bind ligand, or on nuclear translocation of the liganded receptor at either a saturating or subsaturating dose of dexamethasone (DEX). Consistent with the binding data, functionally, neither CsA nor FK506 altered the glucocorticoid induced decrease in either proopiomelanocortin (POMC) derived peptide secretion or POMC heteronuclear (hn) RNA expression. Despite the fact these drugs did not modulate the actions of glucocorticoids on corticotrope cells, both FK506 and CsA were potent stimulators of basal β‐endorphin secretion (4–6 fold) from rat anterior pituitary cultures and AtT20 cells. In addition, FK506 and CsA potentiated β‐endorphin secretion induced by corticotropin releasing factor (CRF) and phorbol ester, but had no apparent acute (60 min) effect on POMC hnRNA levels. Unlike the acute actions of these immunosuppressant drugs, chronic (24 h) treatment lead to a decrease in cytoplasmic POMC mRNA with no apparent change in the amount of secreted β‐endorphin. Taken together these data suggest that FK506 and CsA do not alter GR activation or function in corticotrope cells, however, they are potent but short lived stimulators of POMC‐derived peptide secretion. The observation that CsA and FK506 stimulate POMC‐derived peptide secretion, and potentiate both phorbol ester and CRF induced secretion, suggests that these immunosuppressant drugs are acting upon a common point within these intracellular pathways.
Effect of Perinatal Hypothyroidism on Expression of Cytochrome C Oxidase Subunit I Gene, which is Cloned by Differential Plaque Screening from the Cerebellum of Newborn Rat
Authors: Koibuchi Noriyuki , Matsuzaki Shigeru , Ichimura Kaoru , Ohtake Hideki , Yamaoka Sadao 
Published: September 2006

AbstractEarly development of the central nervous system is influenced by several hormones including thyroid hormone. This study was designed to clone the gene whose expression is changed in association with perinatal hypothyroidism in the rat cerebellum. Rats were sacrificed at 15 day‐old postnatal age (P15) and their cerebella were removed. Poly (A)+ RNA was extracted to construct a cDNA library using λgt 10 cloning vector. Differential plaque screening was then performed using 32P‐labeled antisense cDNA synthesized from poly (A)+ RNA of the methimazole‐treated (hypothyroid) P15 rat cerebellum (hypothyroid probe), and of the euthyroid P15 rat cerebellum (euthyroid probe). The clones, which hybridized strongly to the euthyroid probe and weakly or not at all to the hypothyroid probe, were isolated. Sequence analysis of these clones revealed that all isolated clones encode cytochrome c oxidase subunit I (COX I), which is located in the mitochondria1 DNA. The decrease in COX I gene expression was not seen in the animals, which received methimazole treatment and daily replacement of thyroid hormone. In situ hybridization detection showed not only overall decrease in COX I gene expression but also change in distribution of hybridization signal in the cerebellar cortex of hypothyroid rat. Such change was not observed in the T4‐replaced animals. Based on the evidence that thyroid hormone greatly influences brain development, the results of the present study indicate that the terminal enzyme of mitochondria1 respiratory chain, COX I is one of the important target molecules regulated by thyroid hormone in the newborn rat cerebellum.
Inhibition of Hypothalamic Nitric Oxide Synthase Gene Expression in the Rat Paraventricular Nucleus by Food Deprivation is Independent of Serotonin Depletion
Authors: Ueta Yoichi , Levy Andrew , Chowdrey Hardial S. , Lightman Stafford L. 
Published: September 2006

AbstractWe have investigated the effects of food deprivation on nitric oxide synthase (NOS) transcript levels in the rat paraventricular (PVN) and supraoptic nuclei (SON), using in situ hybridization histochemistry. Food deprivation for 48 h significantly and consistently reduced NOS transcript prevalence by approximately 50% in both sites. Since there is considerable evidence for an important role of 5‐HT in feeding behaviour, we then examined the effect of food deprivation on NOS gene expression in the PVN following para‐chlorophenylalanine (PCPA)‐induced hypothalamic 5‐HT depletion. As starvation causes central down‐regulation of the thyroid axis, changes in thyrotropinreleasing hormone (TRH) and pituitary thyrotrophin (TSH) transcript prevalence were used as internal controls. PCPA pretreatment (200 mg/kg body weight as a single daily dose ip for 2 days) had no significant effect on basal levels of NOS, TRH or TSH transcripts, or on the effect of a subsequent 48 h fast, which significantly reduced all three. These results show for the first time, that food deprivation for 48 h significantly reduces NOS gene expression in the rat PVN and SON. Secondly, that basal levels and the fasting‐induced reductions in the prevalence of NOS, TRH and TSH transcripts were not affected by PCPA‐induced hypothalamic 5‐HT depletion. Therefore, at least under the experimental conditions used here, 5‐HT does not appear to be involved in setting baseline levels—or in the starvation‐induced inhibition of NOS or thyroid axis gene expression in the PVN.
Anorexia Induced by the Parasitic Nematode, Nippostrongylus brasiliensis: Effects on NPY and CRF Gene Expression in the Rat Hypothalamus
Authors: Horbury S. R. , Mercer J. G. , Chappell L. H. 
Published: September 2006

AbstractInfections of the gastrointestinal nematode, Nippostrongylus brasiliensis, in the laboratory rat result in a characteristic biphasic anorexia which is followed by hyperphagia once the worm burden has been cleared. Despite the importance of parasite‐induced anorexia, relatively little is known of the underlying mechanisms. We have investigated the involvement of the central appetite drive in this anorexia by studying the gene expression of two neuropeptides with opposing actions on energy balance, NPY and CRF. Gene expression was assessed by in situ hybridization at 2, 8 and 16 days post‐infection (p.i.) in infected rats, in uninfected controls, and in a group with food intake restricted to match that taken voluntarily by the parasitized animals. The sampling intervals corresponded to each of the two phases of maximum anorexia and the period of compensatory hyperphagia. Surprisingly, we found that increases in NPY gene expression in the hypothalamic arcuate nucleus (ARC) accompany anorexia in rats infected with N. brasiliensis; there was a significant relationship between degree of anorexia and induction of NPY mRNA after 8 days of infection. Furthermore, ARC NPY mRNA levels in parasitized animals were similar to those in pair‐fed individuals with food intake restricted to match the infected rats. The number of larvae used to establish the infection affected both the degree of anorexia and the level of NPY mRNA at 8 days p.i. in a dose‐dependent manner. NPY gene expression remained elevated in infected rats during at least the initial stages of compensatory hyperphagia. This suggests that animals detect a state of energy deficit during the early stages of the infection, yet do not feed, but become hyperphagic coincident with worm loss. The failure of anorectic parasitized animals to feed in response to activation of the NPYergic system makes this a novel system in which to study the regulation of hypothalamic NPY by physiological challenge. There were no significant differences in CRF gene expression between the groups at any of the sampling intervals.
Expression of Early Genes in Estrogen Induced Phenotypic Conversion of Neuroblastoma Cells
Authors: Santagati Sabrina , Ma Zhi Qing , Ferrarini Concetta , Pollio Giuseppe , Maggi Adriana 
Published: September 2006

AbstractEstrogens are known to modulate the growth rate and differentiation state of a number of cells. In uterine, as well as in mammary tumor cells, estrogen‐dependent proliferation and differentiation are correlated to a series of biochemical responses, including increased expression of proto‐oncogenes such as:, c‐fos, c‐jun and c‐myc. Since estrogens were shown to regulate the proliferation and the differentiation state of cells of nervous origin, the aim of the present study was to investigate whether these effects were associated to changes in the expression of early genes. In the model system utilized, the human cell line SK‐ER3, an increase in c‐fos mRNA and Fos protein without change of c‐jun and related genes mRNA concentration was observed after short term treatment with 17β‐estradiol (E2). A significant decrease of c‐fos, c‐jun and jun‐D proto‐oncogene mRNA levels were found after prolonged hormonal treatment. The exposure to the hormone did not determine any change in N‐myc expression. Since the three protooncogene mRNAs are rapidly induced following estrogen treatment in other cell systems and target tissues, it is concluded that the estrogen‐induced differentiation of neuroblastoma cells is correlated to a pattern of expression of early genes that might be peculiar for the activity of this hormone in neural cells.
Gonadotropin‐Releasing Hormone (GnRH) Neurons of the Developing Tectum of the Mouse
Authors: Wu T. J. , Gibson M. J. , Silverman A. J. 
Published: September 2006

AbstractUsing a modified immunocytochemistry protocol with enhanced sensitivity, we were able to visualize a population of neurons in the tectum of the developing mouse that contained GnRH‐like immunoreactivity. In microscopic studies conducted using 100 pm sections cut in sagittal or horizontal planes, 10–20 lightly‐stained neurons were first detected in the tectum at E 13.75 (morning of plug = E0.5). The number of immunostained cells increased exponentially reaching a peak at E 15.75 before decreasing in number. No positive neurons were seen in the tectum at PN20 or later. The GnRH cells were located medially along the dorsoventral axis of the tectum in a region of the brain distinct from that containing GnRH neurons that migrate into the CNS from the olfactory placode. To determine the nature of the immunoreactivity, two approaches were used. Analysis of tissue from an hpg mutant strongly supports the hypothesis that these cells make mammalian GnRH. lmmunocytochemical data suggest that although the precursor protein is synthesized, the cleaved and amidated decapeptide may be absent or be present at an undetectable level. Our results demonstrate that in addition to the GnRH neurons from the placade, a population of GnRH neurons exists in the mouse tectum. This population is developmentally regulated, appearing only during embryonic and early postnatal ages but not in the adult.
Regulation of Pituitary Vasopressin V1b Receptor mRNA during Stress in the Rat
Authors: Rabadan‐Diehl Cristina , Lolait Stephen J. , Aguilera Greti 
Published: September 2006

AbstractPrevious studies have shown a parallel relationship between pituitary vasopressin (VP) receptor content and responsiveness of the corticotroph during chronic stress. The regulation of pituitary VP receptors was further studied by analysis of V1b VP receptor mRNA levels in pituitaries of rats subjected to chronic immobilization, i.p. hypertonic saline injection (physical stress paradigms associated with increased pituitary responsiveness), and water deprivation, or to 2% saline in the drinking water (osmotic stress paradigms associated with decreased pituitary responsiveness). Northern blot hybridization with a 363 bp 32P‐labelled fragment of the rV1b receptor cDNA coding sequence revealed two bands of about 3.7 and 3.2 Kb, whereas a probe directed to the 5′ untranslated region recognized only the 3.7 Kb band. Repeated i.p. hypertonic saline injection, 3 times in 24 h at 8 h intervals, or daily for 8 days, increased the intensity of the 3.7 Kb band by 155 ± 17.5% (P<0.01) and 118 ± 14.6% (P<0.01), respectively, while the 3.2Kb band increased by 122 ± 39.3% (P<0.01) only after 3 times injection. Smaller increases of 39 ± 11 and 33 ± 9% (P<0.05) in the 3.7 Kb band were found after repeated immobilization 3 times in 24 h and 2 h for for 8 days respectively. In situ hybridization studies confirmed significant increases (P<0.05) in V1b receptor mRNA levels after 8 and 14 days repeated immobilization (63 ± 19% and 83 ± 10%) or i.p. hypertonic saline injection (110 ± 13% and 73 ± 20%). In response to acute stress, V1b receptor mRNA increased by 77 ± 5% (3.7 Kb band) after 4 h immobilization for 1 h, whereas both bands were reduced by 49 ± 5% and 45 ± 5%, 4 h after a single i.p. hypertonic saline injection. The decrease in V1b receptor mRNA following a single i.p. hypertonic saline injection was prevented by pretreatment with a V1 receptor antagonist, suggesting that increased VP secretion may account for this effect. In spite of the decrease in V1 b receptor mRNA following i.p. hypertonic saline injection, VP binding in pituitary membrane rich fractions, and VP‐stimulated inositol phosphate formation in quartered hemipituitaries were increased by 24 and 39%, respectively. V1b receptor mRNA levels were unchanged or decreased following prolonged osmotic stimulation.These studies suggest that increased V1b receptor mRNA levels contribute to the VP receptor upregulation observed during repeated immobilization and i.p. hypertonic saline injection, whereas the lack of parallelism between V1b receptor mRNA and VP binding indicates that regulation of steady‐state levels of V1b receptor mRNA is not a primary determinant in the control of pituitary VP receptor concentration during stress.
ACTH‐Suppressive and Vasodilator Actions of Adrenomedullin in Conscious Sheep
Authors: Parkes David G. , May Clive N. 
Published: September 2006

AbstractAdrenomedullin (ADM) is a 52 amino‐acid peptide which is a potent vasodilator in rats, and suppresses basal and CRF‐induced ACTH release from cultured pituitary cells. The present study examines the hemodynamic and hormonal actions of human ADM (1–52) infusion in conscious, chronically instrumented sheep. Five sheep were infused intravenously (IV) or intracerebroventricularly (ICV) with ADM at 100 pg/h for 60 min, and mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), total peripheral conductance (TPC), coronary blood flow (CF), coronary conductance (CC), peak aortic flow (Fmax), and left ventricular dF/dt were monitored by a computer‐based data collection system every 2 min. Plasma concentrations of adrenocorticotropin (ACTH), arginine vasopressin (AVP) and renin were measured after 60 min of infusion. IV ADM produced a small fall in MAP of 3 ± 1 mmHg, associated with a reflex increase in HR of 14 ± 3 b/min. CO increased by 1.3 ± 0.3 1/min, whereas SV remained unchanged. TPC was markedly increased by 20 ± 3 ml/min/mmHg. Changes in CF were also seen with an increase of 10 ± 2ml/min, and CC increased in parallel by 0.15 ± 0.02 ml/min/mmHg. Fmax and dF/dt showed small increases of 2.1 ± 0.5 Vmin and 85 ± 20 1/min/sec respectively. Plasma concentrations of ACTH and cortisol were reduced by 58% and 55% respectively, whereas plasma renin concentration increased by 106%. There was no change in plasma levels of AVP. ICV infusion of ADM had no effect on any parameter measured. These data suggest that systemic ADM produces a sustained vasodilator action to lower blood pressure in sheep, and this is the first study to report the ACTH‐suppressor action of ADM in conscious animals. ADM may therefore be an important hormone involved in the regulation of pituitary/adrenal function, in addition to its cardiovascular and fluid regulatory actions in mammals.