bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of γ-Aminobutyric Acid in the Control of GTH-1 and GTH-2 Secretion in Male and Female Rainbow Trout
Authors: Mañanos Evaristo L. , Anglade Isabelle , Chyb Jaroslaw , Saligaut Christian , Breton Bernard , Kah Olivier
Published: April 2003

The potential role of the neurotransmitter γ-aminobutyric acid (GABA) in the control of the secretion of the two pituitary fish gonadotropins (GTH-1 and GTH-2) was investigated in male and female rainbow trout (Oncorhynchus mykiss). The presence of glutamate decarboxylase-positive fibers in the neurohypophyseal digitations adjacent to the gonadotropic cells was demonstrated by means of double immunohistochemistry, providing a morphofunctional support for potential GABA-gonadotropin interactions in both sexes. In spermiating males, in vivo treatment with GABA did not affect basal gonadotropin release, but stimulated GTH-1 release when coadministered with a gonadotropin-releasing hormone analogue (GnRHa), and potentiated GnRHa-stimulated GTH-2 release. In vitro, using dispersed pituitary cells, GABA stimulated basal GTH-1 and GTH-2 secretion, in a dose-dependent manner, and potentiated salmon GnRH effect on both hormones. In mature females, GABA induced in vivo a strong elevation of plasma GTH-2 levels after 2– 6 h of injection, but had no effect in vitro. GABA treatment in vivo was also stimulatory in recrudescent females, slightly increasing plasma GTH-2 levels in both saline- and GnRHa-treated fish (GnRHa alone has no effect at this stage). Immature fish were unresponsive to GABA/GnRHa treatments but, after steroid implantation [testosterone (T) or estradiol] for 13 days, injection of GABA stimulated GTH-2 release in vivo (also GTH-1 slightly in T-implanted fish). In conclusion, GABA has an overall stimulatory action on GTH-1 and GTH-2 secretion in rainbow trout, which depends on the sex and the reproductive stage of the fish. The stimulatory action of GABA might be exerted, at least in part, directly onto the gonadotropes, as it stimulates basal and GnRH-induced GTH-1 and GTH-2 secretion from dispersed pituitary cells.
Long-Lasting Effects of Stress on Glucocorticoid Receptor Gene Expression in the Rat Brain
Authors: Kitraki Efthimia , Karandrea Despoina , Kittas Christos
Published: April 2003

Stressful stimuli are known to affect glucocorticoid receptor (GR) mRNA levels in the rat brain. The aim of this study was to examine the duration of chronic stress-induced changes in GR gene expression in the male rat hippocampus and cerebellum. By using in situ hybridization histochemistry, we detected a statistically significant down-regulation of GR mRNA both in the hippocampus and in the cerebellum of rats stressed for 8, 10 and 14 days. The same degree of down-regulation could also be detected in the above brain areas of rats stressed for 14 days and left undisturbed for 48 h or 8 days after stress. To examine the effects of subsequent stressors on the expression of down-regulated GR mRNA in the hippocampus of chronically stressed rats, we determined, by Northern blotting, GR mRNA levels in the hippocampi of rats stressed for 14 days and subsequently exposed to either short- or long-duration stressors. The down-regulated levels of GR mRNA remained practically unaffected when a subsequent new stressor was applied. Our results show that chronic stress-induced down-regulation of GR mRNA in the rat brain can be extended for periods longer than the initial/causative stimulus, irrespective of the presence of a novel stimulus.
Characterization of Ionotropic Glutamate Receptors in Rat Hypothalamus, Pituitary and Immortalized Gonadotropin-Releasing Hormone (GnRH) Neurons (GT1-7 Cells)
Authors: Mahesh Virendra B. , Zamorano Pedro , De Sevilla Liesl , Lewis Deborah , Brann Darrell W.
Published: April 2003

Evidence from various sources suggested that the Gonadotropin-Releasing Hormone (GnRH) neuron does not contain glutamate receptors. Northern analysis of the hypothalamus showed the presence of NMDAR1, GluR1, GluR4 and GluR6 mRNA, while the pituitary showed the presence of NMDAR1, GluR1 and GluR6 mRNA. Western blot analysis also showed the presence of NMDAR1 and GluR1 protein. Since there are relatively few GnRH neurons in the hypothalamus, and GT1-7 cells have been considered to be a GnRH neuronal cell line, GT1-7 cells were studied in detail. GT1-7 cells contained NMDAR1 mRNA levels as shown by Northern analysis but did not contain GluR1, GluR4, or GluR6 mRNA. They did not show the presence of NMDAR1 and GluR1 protein by Western analysis. In addition, GT1-7 cells showed no NMDA receptor binding using the competitive inhibitor CGP-39563 and the noncompetitive inhibitor MK-801. Likewise, no binding was detected for kainate receptors. However, a small amount of binding for AMPA receptors was found in GT1-7 cells. GT1-7 cells did not exhibit glutamate toxicity and NMDA failed to elicit inward currents using patch-clamp techniques, although GABA did induce currents in the cells. As a whole, these studies suggest that GT1-7 cells lack or possess only low levels of ionotropic glutamate receptors.
Expression of the L-Type Ca2+ Channel in AtT-20 Cells Is Regulated by Cyclic AMP
Authors: Xie Jiangang , Nagle Gregg T. , Childs Gwen V. , Ritchie Aileen K.
Published: April 2003

Activation of adenylyl cyclase by corticotropin-releasing hormone (CRH) stimulates secretion of adrenocorticotropin (ACTH) in rat anterior pituitary corticotropes and in the murine AtT-20 cell line. The stimulation of secretion is mediated by cAMP and is largely dependent on Ca2+ influx through voltage-gated L-type Ca2+ channels. To investigate whether CRH and cAMP also increase expression of the L-type Ca2+ channel in AtT-20 cells, an RNase protection assay was used to measure the α1C mRNA that encodes the pore-forming subunit of the L-type Ca2+ channel. The α1C mRNA level was measured by autoradiographic densitometry and normalized to the β-actin mRNA level in the same sample. The α1C mRNA was not changed by 24-hour treatment with CRH (10–500 nM). A 24-hour treatment with 1 mM 8Br-cAMP significantly increased the α1C mRNA by 40% over its control. The stimulatory effect was blocked by 2 µM actinomycin D and was, therefore, dependent on gene transcription. The measured half-life of the α1C mRNA, after inhibition of transcription, was 4.7 ± 0.3 h in control and 5.2 ± 0.6 h in the presence of 8Br-cAMP. Thus the 8Br-cAMP- induced increase in α1C mRNA could be due to an increase in α1C gene transcription or to a transcriptionally regulated increase in a protein that helps to stabilize α1C mRNA. Finally, to determine if the increased mRNA was followed by an increase in production of L-type Ca2+ channels, the binding of [3H]PN200-110 to Ca2+ channel proteins was assayed in AtT-20 membrane fragments. 8Br-cAMP increased [3H]PN200-110 binding sites by 32% (Bmax 36.0 ± 1.2 fmol/mg protein in control vs. 47.4 ± 3.2 fmol/mg protein in 8Br-cAMP-treated cells) but did not change the Kd. These studies show that both α1C mRNA and L-type Ca2+ channel protein are increased in AtT-20 cells by cAMP.
Cold Stress and Corticotropin-Releasing Hormone Induced Changes in Messenger Ribonucleic Acid for the α1-Subunit of the L-Type Ca2+ Channel in the Rat Anterior Pituitary and Enriched Populations of Corticotropes
Authors: Xie Jiangang , Nagle Gregg T. , Ritchie Aileen K. , Collins Thomas J. , Childs Gwen V.
Published: April 2003

In response to stress, adrenocorticotropin (ACTH) is secreted from anterior pituitary corticotropes. Corticotropin-releasing hormone (CRH) is a potent stimulator of ACTH secretion. The CRH stimulation of secretion is mediated by cAMP and is largely dependent on Ca2+ influx through voltage-gated L-type Ca2+ channels. This study was designed to investigate whether the expression of L-type Ca2+ channels in the rat anterior pituitary and in corticotropes is regulated by acute stress and CRH. RNase protection assays were used to quantify α1C mRNA of the L-type Ca2+ channel. The α1C mRNA levels from stressed rats increased by 31% in anterior pituitaries of rats after 30 min of exposure to cold stress. Neither 60 min cold stress nor 30 min restraint stress had an effect on α1C mRNA levels. When α1C mRNA was detected by in situ hybridization in a population of corticotropes enriched to 90%, 0.5 nM CRH (3 h) stimulated a 36% increase in the average area of label/cell and a 10% increase in the average density of label. Our results suggest that (1) the expression of α1C subunit mRNA of L-type Ca2+ channels is increased in the rat anterior pituitary with a stress-specific response that might reflect an increase both in thyrotropes and corticotropes (both are known to be stimulated by cold stress), and (2) the CRH-mediated increase in α1C mRNA expression in individual rat corticotropes, in vitro, supports the hypothesis that some of the increase in vivo is due to changes in corticotropes.
Galanin Immunoreactivity in Mouse Basal Forebrain: Sex Differences and Discrete Projections of Galanin-Containing Cells beyond the Blood-Brain Barrier
Authors: Rajendren Gopalan , Levenkova Nataliya , Gibson Marie J.
Published: April 2003

The distribution of galanin-immunoreactive (GAL-IR) cell bodies in the basal forebrain of mice was investigated. The overall pattern of staining for GAL in the area of brain analyzed was similar to that reported in other species with noticeable variations. Distinctive groups of GAL-IR cells were present in the bed nucleus of stria terminalis (BNST), supraoptic nucleus, retrochiasmatic supraoptic nucleus (SOR), magnocellular paraventricular nucleus, arcuate nucleus (ARC) and the nucleus circularis which is one of the cell groups belonging to the accessory magnocellular system. Comparison of the number of GAL-IR cells between the sexes indicated sexual dimorphism in the BNST, SOR and the ARC. As compared with female mice, the mean number of GAL-IR cells/section in the BNST and the SOR was higher and that in the ARC was lower in the males. Unlike in rats, the preoptic area contained mostly scattered GAL-IR cell bodies. Intraperitoneal injection of the retrograde tracer fluoro-gold in male mice resulted in uptake of fluoro-gold by selective GAL-IR cell groups in the basal forebrain suggesting that only some of these cell groups may project outside the blood-brain barrier whereas others may be involved in intracerebral neural transmission.
Monensin and Hypo-Osmolar Medium Cause Calcium-Independent β-Endorphin Secretion from Melanotropes
Authors: Bäck Nils , Soinila Seppo , Törnquist Kid
Published: April 2003

Monensin has been shown to cause nonexocytotic release of catecholamines from adrenal medullary and PC12 cells. We examined the effect of monensin on peptide secretion with cultured melanotropes from the rat pituitary as a model. 1 µM monensin caused an immediate, transient increase in β-endorphin secretion. The effect was still seen in a calcium-free medium, but was totally abolished in a sodium-free medium. Intracellular calcium concentration was measured with Fura 2: no increase was observed during monensin stimulation. Hypo-osmolar medium mimicked the effect of monensin, causing a 12-fold transient increase in β-endorphin secretion. This effect was not abolished in either calcium-free or sodium-free medium. No increase in the number of exocytotic figures captured by tannic acid incubation was observed during 5 min of incubation with 1 µM monensin or hypo-somolar medium. We thus show that monensin causes β-endorphin secretion from the melanotrope and that this effect is due to sodium influx and resultant cell swelling. The calcium independency and lack of increase of exocytotic figures suggest that swelling-induced secretion is nonexocytotic, possibly via transient exocytotic pore opening.
Influence of Different Serotonin Receptor Subtypes On Growth Hormone Secretion
Authors: Valverde Ignacio , Peñalva Angela , Dieguez Carlos
Published: April 2003

The role of serotonin (5-HT) in the regulation of growth hormone (GH) secretion remains unclear due to the existence of many different receptors that mediate the 5-HT actions, and the lack of suitable specific agonist and antagonist drugs. In the present work we have taken advantage of the recent development of new selective 5-HT drugs in order to clarify the role played by different 5-HT receptor types and subtypes on GH secretion. The experiments were carried out on beagle dogs. GH-releasing hormone (GHRH) increased basal canine GH (cGH) levels from 0.8 ± 0.2 to 8.8 ± 1.7 µg/l at 15 min. Administration of 5-HT1D receptor agonist sumatriptan (SUM) induced a cGH peak at 30 min of 12.9 ± 2.7 µg/l. The combined administration of GHRH plus SUM strikingly potentiated cGH release with a peak of 36.9 ± 6 µg/l at 30 min (p < 0.05). Pretreatment with the muscarinic receptor antagonist atropine completely abolished the cGH response to SUM, while the cholinergic agonist pyridostigmine (PYR) did not modify this response (15.3 ± 5 µg/l PYR plus SUM vs. SUM alone 12.9 ± 2.7 µg/l). On the other hand, administration of drugs with activity at 5-HT2A/C receptors showed a stimulatory role for the 5-HT2C receptor subtype, since LY-53857 (antagonist 5-HT2A/C) and DOI agonist (5-HT2A/C) both modified the GH response stimulated by GHRH (AUC 88.5 ± 30.4 and 400 ± 64.6 vs. 267.3 ± 52.6 respectively), while ketanserin (antagonist 5-HT2A) did not modify this response. The 5-HT3 antagonist ICS-205–930 failed to modify either basal or GHRH induced GH responses. In conclusion, our data show that 5-HT1D receptors play a stimulatory role on GH secretion in the dog, possibly by acting through a decrease in hypothalamic somatostatin release. Similarly, the 5-HT2C receptor subtypes also appear to play a stimulatory role. However, 5-HT2A and 5-HT3 receptors do not appear to be involved in the control of basal and GHRH-induced GH secretion.
Estradiol Attenuates the Forskolin-Induced Increase in HypothalamicTyrosine Hydroxylase Activity
Authors: Arbogast Lydia A. , Hyde James F.
Published: April 2003

The purpose of this study was to evaluate interactions between estradiol and the 3′,5′ cyclic adenosine monophosphate (cAMP) signaling pathway to regulate tyrosine hydroxylase (TH) activity in hypothalamic dopaminergic neurons. The first experiment examined the ability of forskolin to activate TH in the tuberoinfundibular dopaminergic neurons of adult ovariectomized rats with or without estradiol treatment. Estradiol treatment reduced both basal and forskolin-stimulated TH activity in the median eminence. The second group of experiments examined the effect of estradiol on the forskolin-induced activation of TH in fetal hypothalamic cells cultures. Estradiol decreased basal TH activity in the hypothalamic cell cultures to 80% of control levels. Forskolin treatment for 1 h increased TH activity in a concentration-dependent manner in control and estradiol-treated cells, but estradiol attenuated the stimulatory response to 0.01–10 µM forskolin. The suppressive effect of estradiol on cAMP-dependent activation of TH was evident with 1–12 h of forskolin treatment. The responses to other activators of the cAMP- protein kinase A pathway, including dibutyryl cAMP and 8-bromo-cAMP, and to a depolarizing stimulus were blunted in estradiol-treated cultures. Forskolin treatment for 1 h increased radiolabeled phosphate incorporation into TH protein in control but not estradiol-treated cells, suggesting that estradiol interferes with the ability of the cAMP pathway to phosphorylate TH. Forskolin caused a time-dependent increase in TH mRNA signal levels in control cultures. The magnitude of the forskolin-induced increase in TH mRNA levels was less in the estradiol-treated cells after 6 h of forskolin treatment, indicating that estradiol hinders cAMP-regulated TH gene expression. These data indicate that estradiol attenuates the ability of hypothalamic dopaminergic neurons to respond to cAMP-dependent stimulation by interfering with phosphorylation mechanisms in the short term and control of TH mRNA levels in the long term.
Melatonin Receptors in the Pituitary of a Teleost Fish: mRNA Expression, 2-[125I]Iodomelatonin Binding and Cyclic AMP Response
Authors: Gaildrat Pascaline , Falcón Jack
Published: April 2003

Melatonin has for a long time been involved in the photoperiodic control of fish physiology (growth, reproduction) and behavior (locomotor activity); but its mechanisms of action are not understood. We show here that 2-[125I]iodomelatonin binds specifically to membrane preparations from Pike (Esox lucius, L.) pituitaries (KD: 556 pM; Bmax: 2.8 fmol/mg proteins). Radioautography indicated that the binding was restricted to a part of the pituitary only. Using polymerase chain reaction from pike genomic DNA, we subcloned two partial cDNAs encoding the P1.4 (Mel1a) and the P2.6 (Mel1b) melatonin receptor subtypes. The two corresponding transcripts were expressed in the pituitary as revealed by RT-PCR assay and Southern blot hybridization. In culture, melatonin inhibited in a time- and dose-dependent manner cyclic AMP levels in pituitaries cultured in the presence of forskolin, an adenylyl cyclase activator. This is the first evidence for the expression of melatonin receptors and binding sites, and for the modulation of a second messenger by melatonin in the pituitary of a nonmammalian species. We suggest that in fish, the melatonin-mediated photoperiodic control of neuroendocrine functions involves, at least, a direct effect on the pituitary.
Maternal Behavior Stimulates c-fos Activity within Estrogen Receptor Alpha-Containing Neurons in Lactating Rats
Authors: Lonstein Joseph S. , Gréco Béatrice , De Vries Geert J. , Stern Judith M. , Blaustein Jeffrey D.
Published: April 2003

Estradiol and other hormones are thought to be critical for the onset, but not maintenance, of maternal behavior in rats. Maternal behavior is instead maintained postpartum by tactile stimulation that dams receive during interactions with pups, and many neural sites implicated in the control of maternal behavior show elevated c-fos activity in response to this stimulation. Many of these sites also contain neurons that express the alpha subtype of the estrogen receptor (ERα). Because of possible interactions between tactile stimulation from pups, c-fos, and ERα in the lactating rat brain, we determined if populations of cells that show increased c-fos activity after maternal behavior in lactating rats also contain ERα. Dams were separated from their pups for 48 h beginning on day 5 postpartum. On day 7 postpartum, experimental dams were reunited with pups and mother-litter interactions were observed for 60 min. Control dams received no pup stimulation. Subjects were sacrificed 60 min later and brain sections were double immunolabeled for the Fos and ERα proteins. As expected, the number of ERα-immunoreactive (ERα-ir) neurons did not differ between the two groups in the eight areas analyzed (lateral region of the lateral septum, posterodorsal medial amygdala, dorsal and ventral medial preoptic area, dorsal and ventral bed nucleus of the stria terminalis, lateral habenula, and ventrolateral caudal periaqueductal gray). Consistent with previous reports, maternal dams had 2- to 7-fold more Fos-immunoreactive (Fos-ir) neurons in these sites compared with nonstimulated controls. Maternal dams had significantly more Fos-ir neurons that also contained ERα-ir in all sites, with the greatest increases in the ventral medial preoptic area, lateral habenula, and ventral bed nucleus of the stria terminalis. Between ∼25 and 45% of the Fos-ir cells in the sites examined also expressed ERα. Thus, a substantial number of neurons that are genomically activated during maternal behavior contain ERα, raising the possibility that the postpartum display of maternal behavior can be influenced by ERα activity.
Fine Topography of Brain Areas Activated by Cold Stress
Authors: Baffi Judit S. , Palkovits Miklós
Published: April 2003

Neuronal activity in response to acute cold exposure was mapped in the central nervous system of adult rats using Fos immunostaining. A single, 3-hour exposure to cold elicited strong Fos-like immunoreactivity in the medial preoptic nucleus that is known as the thermoregulatory center of the brain. By this technique, pontine and medullary thermosensitive areas have been first localized and outlined anatomically. The medullary thermosensitive neurons occupy well-demarcated areas immediately ventral and dorsal to the spinal trigeminal nucleus, termed peritrigeminal and paratrigeminal nuclei, respectively. Cold-sensitive neurons were present in the dorsal part of the pontine reticular formation. Topographically, this area corresponds to the ‘pontine thermoregulatory area’, named on the basis of neurophysiological observations. In addition, thermosensitive neurons were found in the rostral thalamus and zona incerta. Several cell groups that showed strong Fos-like immunoreactivity in our previous pain-related stress experiments were also activated by cold exposure. The midline thalamic, hypothalamic dorsomedial, supramamillary and lateral parabrachial nuclei were targets of cold stress-induced noxious stimuli. Fos-positive neurons established specific topographical patterns in the paraventricular, arcuate, central amygdaloid nuclei, and the nucleus of the solitary tract. The possible involvement of central noradrenergic neurons in stress response to acute cold exposure was investigated by double immunostaining for tyrosine hydroxylase (TH) and Fos. None of the tyrosine hydroxylase positive neurons in the brain stem established Fos-like immunoreactivity, suggesting that the central noradrenergic system may have a minor, if any, role in cold-induced stress responses. Based on the topographical distribution of Fos-activated neurons, this study suggests that in addition to the hypothalamo-pituitary-adrenal axis, some other stress effector systems may play an important role in the maintenance of homeostasis during cold stress.
Expression of Opioid Receptors in Osteoblast-Like MG-63 Cells, and Effects of Different Opioid Agonists on Alkaline Phosphatase and Osteocalcin Secretion by These Cells
Authors: Pérez-Castrillón José L. , Olmos José M. , Gómez José J. , Barrallo Antonio , Riancho José A. , Perera Lorena , Valero Carmen , Amado José A. , González-Macías Jesús
Published: April 2003

We have previously shown that several stressful situations associated with tissue injury determine a decrease in serum osteocalcin concentration. Since reduced osteocalcin production is a marker of decreased osteoblastic activity, this finding could be related to the pathogenesis of osteoporosis secondary to some diseases. Endogenous opioids are involved in stress response. Proenkephalin-derived peptides have been shown to inhibit alkaline phosphatase activity, another marker of bone formation, in the murine cell line ROS-17/2.8. On the other hand, serum osteocalcin has been reported as being low in heroin abusers. We have therefore thought it of interest to study the presence of opioid receptors in the human osteoblast-like cell line MG-63, and to evaluate the effects of different opioid agonists on the secretion of alkaline phosphatase and osteocalcin by these cells. The presence of opioid receptors was studied by means of RT-PCR and immunohistochemistry. RT-PCR studies suggested the presence of specific mRNA for the three types of receptors, and immunohistochemistry clearly showed their occurrence. Osteocalcin synthesis was significantly inhibited by high concentrations of the mu agonists morphine and (D-Ala2,N-MePhe4,Gly5-ol)-enkephalin although no changes were seen with the delta agonist (D-Ala2,D-leu5)-enkephalin. Morphine-induced osteocalcin inhibition was abolished when osteoblastic cells were incubated simultaneously with naloxone, whereas it was potentiated when cells were preincubated with naloxone. None of the opioid agonists modified the secretion of alkaline phosphatase. In conclusion, human osteoblast-like cells MG-63 express the three types of opioid receptors. Endogenous opioids may be involved in the reduction of osteocalcin observed in stressful situations associated with tissue injury.
Estrogen and Tamoxifen Differentially Regulate Beta-Endorphin and cFos Expression and Neuronal Colocalization in the Arcuate Nucleus of the Rat
Authors: Priest Catherine A. , Roberts James L.
Published: April 2003

Estrogen regulates hypothalamic gene expression, synthesis and release of the endogenous opioid peptide β-endorphin (βEND), although a consensus estrogen response element sequence has not been identified in the rat proopiomelanocortin (POMC) gene. POMC gene expression is also regulated by the activation of AP-1 promoter elements, which are known to be estrogen sensitive. The present studies examine whether estrogen modulates the hypothalamic POMC system through a non-classical mechanism involving AP-1 binding proteins such as cFos. Immunohistochemical double-labeling for βEND and cFos was used and immunoreactive (-ir) populations were quantified in the arcuate nucleus and periarcuate area across time using unbiased stereological methods. Ovariectomized rats were injected with 50 µg estradiol (E2), 500 µg tamoxifen citrate (TAM) or both (E2+TAM) and were perfused 1, 2, 4 or 48 h later. E2 rapidly increased numbers of cFos-ir, βEND-ir and doubly-labeled cells after 4 h, and the number of βEND-ir cells remained high 48 h later, suggesting that the stimulatory effects of cFos on POMC in the hypothalamus persist after the cFos signal decays. Treatment with TAM alone did not affect the numbers of immunoreactive cells, although E2+TAM blocked the E2-mediated induction in all immunoreactive populations. Similar effects were seen at the transcriptional level. E2 increased hypothalamic POMC mRNA after 4 h, while TAM treatment or coadministration of E2+TAM did not significantly change the levels of POMC mRNA. Cellular colocalization of βEND-ir and cFos-ir supports a possible intracellular co-regulation of these peptides by an estrogen-dependent mechanism within a subset of hypothalamic neurons. It does not, however, appear that E2 acts directly through an AP-1 site within the POMC gene.
Antagonist of Pituitary Adenylate Cyclase Activating Polypeptide Suppresses Prolactin Secretion without Changing the Activity of Dopamine Neurons in Lactating Rats
Authors: Tohei Atsushi , Matsuzaki Minako , Kogo Hiroshi
Published: April 2003

Pituitary adenylate cyclase activating polypeptide (PACAP) is a relatively new neuropeptide, and it has a potent stimulatory effect on adenylate cyclase activity in rat pituitary cells. However, the role of PACAP in the physiological control of prolactin (PRL) secretion is still unclear. In the present study, we investigated the physiological significance of endogenous PACAP on PRL secretion in lactating rats. On lactation days 7–8, pups were separated from their mother rats for 5 h before the onset of suckling and PACAP6–38 (16 µg), a receptor antagonist, was injected through the lateral ventricle cannula just after the removal of pups. The effects of PACAP6–38 on PRL and oxytocin secretion, and on the activity of tyrosine hydroxylase (TH), were examined after the onset of suckling. Administration of PACAP6–38 inhibited PRL levels in response to suckling, but it did not affect the activity of TH, as measured by DOPA accumulation at 15 min after administration of NSD 1015 (25.0 mg/kg), an L-aromatic amino acid decarboxylase inhibitor, or the plasma concentrations of oxytocin in lactating rats. Injection of α-methyl-p-tyrosine (α-MT; 50 mg/kg), an inhibitor of dopamine synthesis, increased PRL levels, and suckling caused a further increase in the plasma concentrations of PRL. An injection of PACAP6–38 (i.c.v.) also inhibited the PRL response to suckling under dopamine depletion. These results suggest that endogenous PACAP acts as a neurotransmitter or neuromodulator within the hypothalamus and plays an important role for PRL secretion in lactating rats. Endogenous PACAP may regulate PRL secretion, possibly mediated by PRL-releasing factors such as vasoactive intestinal polypeptide or vasopressin.
Norepinephrine Dialysate Levels in the Hypothalamic Paraventricular Nucleus: Influence on Photoperiod-Driven Prolactin Levels in the Female Siberian Hamster
Authors: Dodge James C. , Badura Lori L.
Published: April 2003

Basal prolactin (PRL) levels in Siberian hamsters are modulated by ambient photoperiod via the nocturnal melatonin signal. Recent evidence from our laboratory has demonstrated that norepinephrine (NE), a putative neurochemical regulator of PRL secretion shows photoperiod-dependent fluctuations in the hypothalamic paraventricular nucleus (PVN) that are independent of the pineal melatonin signal. NE content in the PVN is elevated under a short-day photoperiod with a time course that follows the short-day-induced decline in PRL. NE could thus modulate the release of a prolactin-releasing factor that subsequently drives PRL synthesis and release rates. In order to determine whether NE release in the PVN correlates with basal PRL levels, this study evaluated the relationship between extracellular NE levels in the PVN and basal PRL under long- and short-day photoperiod conditions. In addition, the profile of NE during the proestrous surge of PRL was investigated. Female Siberian hamsters were housed either in long-day or short-day photoperiods for 8 weeks. After 6 weeks of photoperiod exposure, the animals were implanted with a stainless steel guide cannula aimed at the PVN. Two weeks later, the animals were fitted with a jugular cannula for serial blood sampling and implanted with an indwelling microdialysis probe. Dialysis samples were collected every 20 min for 5 h (12.00–17.00 h) from short-day-exposed animals and from long-day-exposed animals classified as being either in diestrus or proestrus. Blood samples were collected every hour and analyzed for PRL levels by radioimmunoassay. NE and methoxy-4-hydrophenylglycol (MHPG) levels were significantly higher in short-day-exposed animals, correlating with the suppressed basal secretion of PRL. Both long-day groups had lower NE and MHPG levels, and higher PRL, than the short-day group. However, long-day animals showed a significant decline in NE in proestrus just prior to the onset of the afternoon surge of PRL. These data suggest that NE released within the PVN participates in the regulation of photoperiod effects upon PRL secretion, as well as that of the afternoon surge of PRL on proestrus.
Hypothalamo-Pituitary-Adrenal Axis Sensitization after Chronic Salt Loading
Authors: Amaya Fumimasa , Tanaka Masaki , Hayashi Seiji , Tanaka Yoshifumi , Ibata Yasuhiko
Published: April 2003

Hypothalamic parvocellular vasopressin (VP) and corticotropin-releasing hormone (CRH) in the paraventricular nucleus (PVN) are major secretagogues of corticotropin (ACTH), and central plasticity including their alteration is closely related to hypothalamic-pituitary-adrenal (HPA) axis modulation. Chronic hyperosmotic stress caused by 2% salt lodaing has been known to alter VP and CRH expression. We recently reported that rehydration, a recovery stage from salt loading, induced a prolonged increase in parvocellular VP mRNA expression and suggested that rehydration can modulate HPA axis function without obvious external stress. In the present study, we examined hypothalamic VP and CRH mRNA expression and their responsiveness to acute immobilization stress in control, salt-loaded and rehydrated animals, in order to clarify the precise mechanism of HPA axis regulation during rehydration. The results were further compared with plasma corticosterone and ACTH levels. Plasma corticosterone decreased during salt loading, whereas it increased during rehydration at 1 week. Basal ACTH concentration increased in 1-week-rehydrated animals, with enhanced responsiveness to the acute immobilization stress. In the hypothalamic parvocellular PVN, basal CRH mRNA levels also decreased during salt loading and increased during rehydration. Basal VP mRNA was up-regulated during both salt loading and rehydration. VP mRNA responded to additional acute stress during salt loading and rehydration, but CRH mRNA did not. These results indicate that the HPA axis activity of parvocellular neurons is still altered at 1 week of rehydration and that VP plays a dominant role in regulating ACTH release in response to acute stress. This rehydration stage may thus be a good model for analysis of post-stress sensitization of the HPA axis.
Hypothalamic Circuitry of Neuropeptide Y Regulation of Neuroendocrine Function and Food Intake via the Y5 Receptor Subtype
Authors: Campbell Rebecca E. , ffrench-Mullen Jarlath M.H. , Cowley Michael A. , Smith M. Susan , Grove Kevin L.
Published: April 2003

Neuropeptide Y (NPY) displays diverse modes of action in the CNS including the modulation of feeding behavior, gonadotropin releasing hormone release, and stress responses. Many of the above physiological actions have been at least partially attributed to actions of NPY on the NPY Y5 receptor subtype. We utilized an antibody directed against the NPY Y5 receptor to characterize the distribution of this receptor in the rat brain. Using Western blot analysis, this antibody recognized a single major band at approximately 57 kD. To further verify the specificity of the antibody, animals were treated for 5 days with antisense oligonucleotides for the Y5 receptor. The antisense treatment significantly reduced food intake and body weight. Furthermore, the Y5 antibody detected a significant decrease in Y5 receptor protein. Y5-like immunoreactivity (-ir) was observed throughout the hypothalamus, thalamus, hippocampus and cortex. Double-label immunofluorescence demonstrated that Y5-ir was colocalized with the following neuronal phenotypes in the hypothalamus, gonadotropin-releasing hormone, neurophysins, corticotropin-releasing hormone, and γ-amino butyric acid. In addition, functional interactions were demonstrated by the presence of close appositions of NPY fibers with Y5-ir expressing cells. The wide distribution of the Y5 receptor-ir, as well as the colocalization within specific neuronal populations, agrees with the distribution of the Y5 receptor mRNA and the known physiological roles of the NPY/Y5 system. The role of the NPY/Y5 receptor system as a mediator between signals of peripheral energy availability and reproductive neuroendocrine function is discussed.
Effect of Long-Term Treatment with the Antiestrogen EM-652.HCl on Pituitary Estrogen Receptor Alpha and Prolactin mRNA Expression in Intact, Ovariectomized and Gonadotropin- Releasing Hormone-Treated Female Rats
Authors: Pelletier Georges , El-Alfy Mohamed , Labrie Claude , Martel Céline , Labrie Fernand
Published: April 2003

Estrogen receptor α (ERα) is the predominant estrogen receptor subtype in the anterior pituitary gland. In order to assess the influence of the pure antiestrogen EM-652.HCl on ERα gene transcription, we have studied the effect of long-term administration of the antiestrogen in ovariectomized rats as well as in intact female rats treated or not with the GnRH-agonist D-trp6, des-Gly-NH210 GnRH ethylamide (GnRH-A), a treatment which induces pharmacological castration. To evaluate the degree of pituitary responsiveness to changes in estrogen exposure, prolactin (PRL) mRNA levels were also measured. ERα and PRL mRNA levels were evaluated by quantitative in situ hybridization. It was found that, 49 weeks after ovariectomy (OVX), pituitary ERα mRNA levels were decreased by 55%. Long-term administration (49 weeks) of EM-652.HCl to OVX animals resulted in a further 41% decrease in ERα mRNA. On the other hand, ovariectomy induced an 82% decrease in PRL mRNA levels while the administration of EM-652.HCl to OVX animals did not further decrease PRL mRNA. The administration of EM.652.HCl or GnRH-A alone to intact rats during 52 weeks did not significantly modify pituitary ERα mRNA levels. Concomitant administration of both GnRH-A and EM-652.HCl induced 41 and 47% decreases in ERα mRNA levels, when compared to the levels measured in vehicle-treated and GnRH-treated animals respectively. Combined administration of EM.652.HCl and GnRH-A induced 56 and 65% decreases in PRL mRNA, respectively. When EM-652.HCl was administered concomitantly with GnRH-A, the inhibitory effect on PRL mRNA levels was more marked than that observed in GnRH-A-treated animals. The present data demonstrate that when circulating estrogens are absent or maintained at very low levels by GnRH administration, EM-652.HCl can still depress ERα gene transcription. It is suggested that estrogens can positively regulate pituitary ERα gene transcription and that the antiestrogen EM-652.HCl can downregulate by itself pituitary ERα gene transcription.
A New Point Mutation in the COL4A5 Gene Described in a Spanish Family with X-Linked Alport Syndrome
Authors: Palenzuela Lluís , Callís Lluís M. , Vilalta Ramon , Vila Ángel , Nieto José L. , Meseguer Anna
Published: April 2003

Background/Aim: Alport syndrome is a hereditary glomerulonephritis, X-linked in 85% of the cases. This form is associated with mutations in the COL4A5 gene which encodes the α5 chain of type IV collagen. We have performed the mutational analysis of the COL4A5 gene in a Spanish family with X-linked Alport syndrome. Methods: We have analyzed three polymorphic markers close to the gene to confirm the X chromosome linkage. By means of the PCR technique, we have screened the 51 exons of the gene. Results: The segregation of the alleles from the analyzed markers was in agreement with the X linkage. Direct sequencing of PCR-amplified products has shown a CCT-to-CTT change in exon 25, resulting in substitution of a proline for a leucine at position 619 of the polypeptide chain (nucleotide 2058). Conclusions: Although proline is considered a nonconserved amino acid, it is essential, upon hydroxylation, in the maintenance of a stable alpha chain triple-helix collagen. Furthermore, the change cosegregates with the disease in all affected members of the family, not being present in 80 control chromosomes. This represents a new mutation in the COL4A5 gene found in the Spanish population.
Bismuth Subcitrate Nephrotoxicity
Authors: Sarikaya Metin , Sevinc Alper , Ulu Ramazan , Ates Fehmi , Ari Fahri
Published: April 2003

Bismuth subcitrate is a known nephrotoxic agent that may lead to acute oliguric renal failure when ingested in toxic doses. We report a 17-year-old girl who was admitted to the emergency room with complaints of nausea, vomiting, and anuria. She had taken 25 tablets containing 300 mg bismuth subcitrate (total 7.5 g). The patient was managed with hemodialysis started a week after ingestion. Bismuth subcitrate nephrotoxicity should be considered in the differential diagnosis of acute renal failure.
Delay between Stroke Onset and Emergency Department Evaluation
Authors: Goldstein L.B. , Edwards M.G. , Wood D.P.
Published: April 2003

Background: Public educational programs have been developed to reduce delays between the onset of ischemic stroke symptoms and emergency department evaluation. An increase in the proportion of patients presenting soon after stroke would reflect the effectiveness of these efforts. Methods: All patients (n = 506) with ischemic stroke admitted to an academic medical center located within the ‘Stroke Belt’ of the USA were prospectively identified over 2 years (1998–1999). Demographics, stroke characteristics and time from symptom onset to arrival in the emergency department were recorded. Results: A higher proportion of ischemic stroke patients presented within 3 h of symptoms in 1998 than in 1999 (18% of 234 vs. 8% of 272, p = 0.0001). Those with less severe strokes (Canadian Neurological Scale score; Spearman r = 0.18, p < 0.0001) and younger patients (r = –0.09, p = 0.04) had greater delays. There was no difference in time to presentation based on race (13% of whites and blacks presented within 3 h, p = 0.70) or sex (16% of women vs. 9% of men, p = 0.10). Logistic regression showed that time to presentation was independently related to both stroke severity and year. Conclusions: These data show that, after accounting for other variables, the proportion of stroke patients presenting within 3 h of symptom onset to one academic medical center decreased by 10% between 1998 and 1999. Revision of public stroke-related educational programs may need to be considered.
Alcohol Drinking and Risk of Hemorrhagic Stroke
Authors: Klatsky Arthur L. , Armstrong Mary Anne , Friedman Gary D. , Sidney Stephen
Published: April 2003

In view of conflicting prior reports, we prospectively studied associations between alcohol consumption and subsequent hospitalization for hemorrhagic stroke (HS) in 431 persons. Alcohol use was determined at examinations in 1978–1984 among 128,934 members of a prepaid health plan. Cox proportional hazards models, with 6 covariates, yielded the following multivariate relative risks (95% CI’s) for HS: lifelong abstainers (ref) = 1.0, exdrinkers = 0.9 (0.5–1.5), persons drinking <1/month = 1.1 (0.8–1.4), >1/month; <1 drink/day = 0.7 (0.5–0.9), 1–2/day = 0.8 (0.6–1.1), 3–5/day = 1.0 (0.6–1.5), 6+/day = 1.9 (1.0–3.5). Relationships to alcohol were similar for subarachnoid (31% of HS) or intracerebral hemorrhage (69% of HS) and in men or women. Beverage choice (wine, beer, and liquor) was not independently related. We conclude that only heavy drinking is weakly related to increased HS risk and that light drinking need not be proscribed with respect to HS risk.
Large Vestibular Aqueduct Syndrome Presenting with Mixed Hearing Loss and an Intact Mobile Ossicular Chain
Authors: Mamıkoğlu Bülent , Bentz Brandon , Wiet Richard J.
Published: April 2003

The majority of patients with large vestibular aqueduct syndrome (LVAS) present with progressive sensorineural hearing loss. Some patients with LVAS also have a mixed hearing loss with conduction components ranging from 15 to 40 dB. In this paper, we report a child with LVAS who presented with a moderate mixed hearing loss which appeared following a head trauma. Exploration of the middle ear revealed an intact and mobile ossicular chain. Opening of the inner ear showed a moderate gusher. Aspects of the issue that LVAS might present with a combined sensorineural and conductive hearing loss are discussed.
Treatment of Bipolar Depression, a Review of the Literature and a Suggestion for an Algorithm
Authors: Nolen Willem A. , Bloemkolk Dieneke
Published: April 2003

A review of the methodology and results of 9 controlled studies on the acute treatment of bipolar depression and the risk of switches into (hypo)mania is presented. There are indications but no proof for efficacy of mood stabilizers such as lithium, carbamazepine and valproate. Only lamotrigine has been shown to be effective, with a relative low risk of switching. Several antidepressants appear effective as well, but again there is no (placebo-controlled) proof of their efficacy. The only exception is tranylcypromine which has been found to be more effective than imipramine. The switch ratio into (hypo)mania by tricyclic antidepressants seems to be higher than by several other antidepressants, especially the selective serotonin reuptake inhibitors. In the acute treatment of bipolar depression, it is recommended to start with a mood stabilizer, and to add an antidepressant after 4–6 weeks in case of nonresponse. In severer cases, one might consider to start earlier with the combination of a mood stabilizer and an antidepressant, and in refractory patients, there is a place for tranylcypromine. In the maintenance treatment, there are indications that the combined treatment of a mood stabilizer (mostly lithium) and an antidepressant (TCA) is associated with an increased risk of switches into (hypo)mania, when compared to a mood stabilizer alone. Therefore, it is recommended to try whether a monotherapy with a mood stabilizer is effective, before combining it with an antidepressant.
New Insights into the Mechanisms and Sites of Action of Lamotrigine
Authors: Langosch J.M. , Zhou X.-Y. , Grunze H. , Walden J.
Published: April 2003

This study was aimed at investigating the effects of lamotrigine (LTG) on electrically evoked field excitatory postsynaptic potentials (fEPSP) and population spikes in the CA1 hippocampal region of guinea pigs. The concentration response curves showed different actions of LTG on fEPSP and on population spikes. The data are in contrast to previous findings that suggest the drug acts primarily on presynaptic sites via a blockade of the release of excitatory amino acids. In the range of therapeutic plasma levels, synaptic transmission was not affected.
Lithium-Induced EEG Changes in Patients with Affective Disorders
Authors: Schulz C. , Mavrogiorgou P. , Schröter A. , Hegerl U. , Juckel G.
Published: April 2003

In 12 patients with affective disorders (ICD-10: F31, F32, F33), EEGs were recorded before and after 4.4 months of lithium treatment. Effects of lithium on the EEG were analyzed by power spectral analysis controlled for vigilance. We found (1) an increase in relative power in both delta and theta band which was related to the lithium plasma level, (2) a decrease in relative alpha power especially at occipital leads and (3) a reduction of the dominant alpha frequency. The changes in relative power were more pronounced in the right hemisphere, which is in contrast to the hypothesis of a site-specific localization of lithium effects only in left anterior regions.
Levels of Monocyte Reactive Oxygen Species Are Associated with Reduced Natural Killer Cell Activity in Major Depressive Disorder
Authors: Frank Matthew G. , Hendricks Shelton E. , Bessette Diane , Johnson Donald R. , Wieseler Frank Julie L. , Burke William J.
Published: April 2003

Major depressive disorder (MDD) is associated with reductions in natural killer cell activity (NKCA), however the mechanism(s) mediating reduced NKCA in MDD has yet to be determined. In light of evidence that MDD is associated with an inflammatory immune response, we propose that reactive oxygen species (ROS), generated by inflammatory leukocytes (monocytes and/or neutrophils), may mediate the suppression of NKCA in MDD. Intracellular levels of monocyte ROS were significantly associated with reductions in NKCA in outpatients (n = 15) diagnosed with MDD. Sleep disturbance was also significantly correlated with reductions in NKCA. Elevated levels of ROS may be an additional characteristic of a subset of depressed patients in whom an inflammatory response persists and elevations in ROS may, in part, mediate the associations observed between MDD, cardiovascular disease, and cancer.
Association between the Ser9Gly Polymorphism of the Dopamine D3 Receptor Gene and Tardive Dyskinesia in Chinese Schizophrenic Patients
Authors: Liao Ding-Lieh , Yeh Yu-Chi , Chen Hung-Mei , Chen Hung , Hong Chen-Jee , Tsai Shih-Jen
Published: April 2003

It has been suggested that dopamine D3 receptor (DRD3) may have important implications for antipsychotic-induced tardive dyskinesia (TD). Previous studies have demonstrated an association between a serine to glycine polymorphism in the first exon of the DRD3 gene and TD; however, the results have been inconsistent. Therefore, we have replicated these studies using a Chinese sample population. A total of 115 schizophrenic patients from chronic wards were assessed for TD severity using the Abnormal Involuntary Movements Scale (AIMS) and were subsequently genotyped for the DRD3 polymorphism. The mean AIMS score for patients carrying the heterozygote (DRD3ser-gly) was significantly greater than for those with the homozygotes (DRD3ser-ser and DRD3gly-gly). Our results are in line with a previous report, the results of which suggest that the presence of the DRD3ser-gly genotype may be a risk factor for the development of TD in patients treated with antipsychotics.