bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced Leptin Levels in Human Narcolepsy
Authors: Schuld Andreas , Blum Werner F. , Uhr Manfred , Haack Monika , Kraus Thomas , Holsboer Florian , Pollmächer Thomas
Published: April 2003

Recently, hypocretins have been implicated in the pathophysiology of narcolepsy, a sleep disorder characterized particularly by the occurrence of excessive daytime sleepiness and cataplexy. Hypocretins, which stimulate food intake, have been reported to be absent in the cerebrospinal fluid (CSF) of the majority of patients suffering from narcolepsy. Because these patients also display an increased body mass index (BMI), it has been suggested that disturbances in metabolism and food intake regulation may be present. To further investigate these presumed alterations, we studied the production of leptin, a fat-cell-derived hormone signaling to the brain the size of the adipose tissue. We measured the levels of leptin in serum and CSF from 15 narcoleptic patients and compared the results to those from age-, sex- and BMI-matched control groups of depressive patients and patients suffering from a noninflammatory neurological disorder. Compared to both control groups, leptin levels in serum, but not in the CSF, were significantly reduced in narcoleptic patients by more than 50%. These results support the hypothesis that human narcolepsy is accompanied by complex alterations of the regulation of food intake and metabolism. The significance of these alterations for the core symptomatology of narcolepsy should be a target of future research.
Gonadotropin-Releasing Hormone Fibers Innervate the Pituitary of the Male African Catfish (Clarias gariepinus) during Puberty
Authors: Dubois Eline A. , Zandbergen Matthijs A. , Peute Jan , Hassing Ine , van Dijk Wytske , Schulz Rüdiger W. , Goos Henk J. Th.
Published: April 2003

The development of the catfish gonadotropin-releasing hormone (cfGnRH) fiber network in the pituitary of male African catfish (Clarias gariepinus) was investigated in relation to puberty. Double immunolabeling studied by confocal laser scanning microscopy revealed a concomitant development of gonadotropes and of pituitary cfGnRH innervation during the first wave of spermatogenesis. Catfish GnRH-immunoreactive fibers in the proximal pars distalis (PPD) of the pituitary were initially observed at the age of 10 weeks (onset of spermatogonial proliferation) and gradually reached the adult pattern at the age of 20 weeks (spermatozoa present in the testis). The content of cfGnRH-associated peptide (cfGAP, part of the prohormone) in the pituitary similarly increased during puberty. At the electron microscopical level, fibers containing cfGAP-ir granules came into close proximity of the gonadotropes at 18 weeks of age. In vitro studies indicated a progressively increasing basal and cfGnRH-stimulated luteinizing hormone (LH) secretion during pubertal development. The LH secretion patterns were similar in response to exogenous cfGnRH (0.1 µM) or to endogenous cfGnRH, the release of which was induced by forskolin (1 µM). Castration experiments demonstrated that the innervation of the pituitary with cfGnRH fibers continued after surgery, accompanied by an increase in the cfGAP levels. However, gonadotrope development was retarded, suggesting a differential regulation of the two maturational processes. Since testosterone stimulates both processes, other testicular factors may also be involved. Puberty-associated changes in LH release patterns appear to reflect changes in the GnRH sensitivity and in the pool of releasable LH, while availability of cfGnRH does not appear to be a limiting factor.
Effects of Photoperiod and Ambient Temperature on the Gonadotropin-Releasing Hormone Neuronal System in the Gray Hamster, Tscherskia triton
Authors: Kawamoto Keiichi , Tanaka Susumu , Kawano Masako , Hayashi Toshiyuki , Tsuchiya Kimiyuki
Published: April 2003

In seasonal breeders like the hamster, gonadal function depends on the photoperiod. The present study examined the effects of different photoperiods and ambient temperatures on the gonadotropin-releasing hormone (GnRH) neuronal system in male gray hamsters, Tscherskia triton. Hamsters were kept from birth under a long-day (LD: 16 h light and 8 h dark) photoperiod and at 23°C until the experiment began. The animals were then kept for 30 days under different photoperiods and ambient temperatures. After autopsy, immunocytochemical and semiquantitative reverse transcription-polymerase chain reaction analyses were performed on the hamster forebrain. Exposure to a short-day (SD: 8 h light and 16 h dark) photoperiod at 23°C induced a functional decline in the GnRH neuronal system (increased neuron number and immunoreactivity, and reduced cell size). LD with low ambient temperature (7°C) did not influence the GnRH neuronal system. In contrast, SD with low ambient temperature enhanced the SD-induced functional decline in GnRH neurons. Changes in immunoreactivity of GnRH fibers in the median eminence, their release site, were also similar to those in neuronal perikarya. Significant differences in GnRH gene expression were detected in the SD only group and the SD with low ambient temperature group. However, no differences were detected between the two groups. These findings suggest that low ambient temperature enhanced the SD-induced decline in GnRH release from nerve terminals, but was not a crucial factor in the synthesis of this decapeptide.
Developmentally and Regionally Regulated Expression of Growth Hormone Secretagogue Receptor mRNA in Rat Brain and Pituitary Gland
Authors: Katayama Masateru , Nogami Haruo , Nishiyama Junichirou , Kawase Takeshi , Kawamura Koki
Published: April 2003

Distribution and development of growth hormone secretagogue receptor (GHS-R) mRNA expression in rat brain and pituitary gland were examined using ribonuclease protection assay. In adult male rats, GHS-R mRNA levels were highest in the pituitary gland, whereas those in the hypothalamus and hippocampus were 57 and 30% of those in the pituitary gland, respectively. Less abundant but detectable levels of GHS-R mRNA were found in the midbrain, pons, and medulla oblongata, but expression was barely detectable in the cerebellum and cerebral cortex. The expression of GHS-R mRNA was detected at late gestation (embryonic day 19) in the pituitary gland, hypothalamus, and brainstem. The mRNA levels increased with age in the pituitary gland, and decreased postnatally in the brainstem, while they remained constant in the hypothalamus during development. In contrast, GHS-R mRNA was not detectable in the hippocampus during the fetal period, but was first detected on postnatal day 7. Expression of GHS-R mRNA was also examined in the spontaneous dwarf rat (SDR), a model for isolated GH deficiency, to examine alterations in GHS-R mRNA expression in a GH-deficient state. GHS-R mRNA levels in the pituitary gland of SDRs were higher than those of control rats, suggesting negative regulation of GHS-R mRNA by GH in this region. GHS-R mRNA levels increased in the hypothalamus of female, but not in male SDRs. In contrast, GHS-R mRNA levels were not affected by GH in the brainstem and hippocampus. These results indicate that region-specific, developmentally regulated expression of GHS-R mRNA may reflect divergent physiological roles of GHS/GHS-R in distinct regions of the central nervous system and the pituitary gland.
Food Intake-Induced Leptin Secretion Modulates Hypothalamo-Pituitary-Adrenal Axis Response and Hypothalamic Ob-Rb Expression to Insulin Administration
Authors: Giovambattista Andrés , Chisari Andrea N. , Gaillard Rolf C. , Spinedi Eduardo
Published: April 2003

The mutation of the ob gene is known to induce a phenotype of obesity accompanied by symptoms including enhanced production of glucocorticoid. Chronic administration to ob/ob mice of leptin, the ob gene product, reverses hypercorticosteronemia. This establishes a clear relation between adipocyte and hypothalamo-pituitary-adrenal (HPA) axis functions. In the present study we investigated the acute modulatory effects of food intake-stimulated leptin secretion on HPA axis activity and hypothalamic leptin receptor (Ob-Rb) expression in 24-hour fasting, adult female, BALB/c mice after insulin-induced hypoglycemia. Our results indicate that: (1) food supply for 45 min to 24-hour fasting mice increased plasma glucose levels and reversed both hypercorticosteronemia and hypoleptinemia; (2) the insulin-induced hypoglycemia produced a marked HPA axis activation in animals with no access to food but this response was fully prevented by food intake and the consecutive increase in plasma leptin levels; (3) the inhibitory effect of leptin on the HPA axis response to insulin-induced hypoglycemia was corroborated by i.p. administration of murine leptin, and (4) fasting-induced hypothalamic Ob-Rb overexpression is not modulated by insulin itself but by leptin, since increase in leptin levels by food intake or by administration of exogenous leptin completely reversed this Ob-Rb overexpression. These results confirm the inhibitory effect of leptin on the HPA axis response to various stress stimuli. They clearly demonstrate that acute food intake in 24-hour fasting mice: (a) rapidly reduced fasting-induced hypercorticosteronemia by enhancing both spontaneous and insulin-elicited endogenous leptin secretion; (b) fully prevented HPA axis response to insulin administration, by rapidly increasing endogenous leptin secretion and probably also by diminishing the extent and the duration of insulin-induced hypoglycemia, and (c) abolished hypothalamic Ob-Rb overexpression induced by fasting itself combined with insulin treatment. The present data strongly suggests an inhibitory effect of endogenous leptin on insulin-induced HPA axis response, an interaction relevant to the physiological adaptation to starvation and caloric excess, and further supports the pivotal role played by the hypothalamus in restoring homeostasis in different allostatic states.
Dopaminergic Input to the Ventromedial Hypothalamus Facilitates the Oestrogen-Induced Luteinizing Hormone Surge in Ewes
Authors: Anderson Stephen T. , Walsh John P. , Tillet Yves , Clarke Iain J. , Curlewis Jonathan D.
Published: April 2003

In this study we examined the release of dopamine and noradrenaline in the ventromedial hypothalamus (VMH) of ovariectomized ewes during the oestrogen-induced luteinizing hormone (LH) surge by measuring their respective metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and methoxyhydroxyphenylglycol (MHPG) using microdialysis. Further we investigated whether inhibition of catecholamine synthesis in the VMH by bilateral reverse dialysis of α-methyl-p-tyrosine (α-MPT) would block the oestrogen-induced LH and/or prolactin surges. Oestradiol treatment (50 µg oestradiol benzoate) of ovariectomized ewes resulted in a biphasic LH response, significantly (p < 0.05) decreasing LH concentrations from 2.5 to 10.5 h after injection, followed by an LH surge beginning at 16 h. Prolactin concentrations were also significantly (p < 0.05) increased in oestradiol-treated ewes from 13 h. VMH DOPAC concentrations in oil-vehicle-treated animals were at the level of detection (0.02 ng/ml) in most samples over the 24-hour sampling period. In oestradiol-treated ewes, VMH DOPAC levels were initially low before and up to 8 h after oestradiol injection but then increased significantly (p < 0.05) at 10–12 h and remained elevated up to 20 h after injection. In contrast, oestradiol injection had no effect on MHPG concentrations in the VMH. Bilateral reverse microdialysis of α-MPT into the VMH significantly (p < 0.05) delayed the time from oestradiol injection to the onset of the LH surge, the time to peak LH concentration and attenuated the LH surge compared with reverse dialysis of Ringer solution alone. In contrast, α-MPT treatment had no effect upon the oestradiol-induced increase in prolactin concentrations. This study provides evidence that the VMH is an important hypothalamic site in the neuro-endocrine control of the LH surge in ewes. The results suggest that dopaminergic neurons with terminals in the VMH are part of a neuronal pathway mediating the positive feedback effects of oestradiol on gonadotropin-releasing hormone secretion and the LH surge.
Estrogens Act in Rat Hippocampus and Frontal Cortex to Produce Rapid, Receptor-Mediated Decreases in Serotonin 5-HT1A Receptor Function
Authors: Mize Amy L. , Poisner Alan M. , Alper Richard H.
Published: April 2003

Previously our laboratory has shown that 17β-estradiol in vivo rapidly decreases R(+)-8-OH-DPAT-stimulated [35S]GTPγS binding (a measure of the initial biochemical event in the intracellular signaling pathway associated with 5-HT1A receptors) in the hippocampus, frontal cortex and amygdala. Studies were designed to determine if 17β-estradiol also acts in vitro on estrogen receptors in the hippocampus and frontal cortex to decrease 5-HT1A receptor function. Hippocampus and frontal cortex were dissected from ovariectomized rats and incubated for up to 3 h with various estrogens and antiestrogens; membrane homogenates were prepared for R(+)-8-OH-DPAT-stimulated [35S]GTPγS binding assays. 17β-Estradiol (10–6 M) decreased the maximal response in the R(+)-8-OH-DPAT-stimulated [35S]GTPγS binding assay in a time-dependent manner (observed at 30, 60 and 120 min) in both hippocampus and frontal cortex. The hormone, however, did not alter the EC50 of R(+)-8-OH-DPAT. When hippocampus and frontal cortex were incubated in graded concentrations of 17β-estradiol for 1 h, the calculated EC50 was approximately 2.5 × 10–8 M in both brain regions. The nonestradiol estrogen diethylstilbestrol also decreased 5-HT1A receptor function while the less potent estrogens 17α-estradiol and estriol were inactive at 5 × 10–8 M. The estrogen receptor antagonist ICI 182,780 potently and completely blocked the effects of 17β-estradiol on 5-HT1A receptor function with an apparent KB of approximately 10–9 M. These data demonstrate clearly that estrogens can act on estrogen receptors located in hippocampus and frontal cortex of ovariectomized rats to produce rapid heterologous decreases in 5-HT1A receptor function.
Glucose and Insulin Increase the Transport of Leptin through the Blood-Brain Barrier in Normal Mice but Not in Streptozotocin-Diabetic Mice
Authors: Kastin Abba J. , Akerstrom Victoria
Published: April 2003

Since fasting is one of the few factors found to change the rate of entry of leptin into brain, we used multiple-time regression analysis to study the effects of pretreatment with glucose or insulin on leptin transport across the blood-brain barrier (BBB). Two hours after intraperitoneal injection of glucose (3 g/kg), there was a statistically significant increase in the entry rate (Ki) of leptin in fasted (from 4.91 ± 0.70 × 10–4 ml/g min to 9.03 ± 1.00 × 10–4 ml/g min) but not (p = 0.15) in nonfasted normal (from 4.90 ± 1.21 × 10–4 ml/g min to 6.42 ± 1.79 × 10–4 ml/g min) or fasted streptozotocin (STZ)-treated diabetic mice (from 4.043 ± 0.959 × 10–4 ml/g min to 5.395 ± 1.355 × 10–4 ml/g min). Insulin (10 U/kg) increased leptin influx in fasted (from 4.77 ± 0.26 × 10–4 ml/g min to 10.6 ± 0.15 × 10–4 ml/g min at 0.5 h) and nonfasted (from 4.64 ± 0.75 × 10–4 ml/g min to 7.46 ± 1.48 × 10–4 ml/g min at 0.5 h) normal mice, but not in STZ-diabetic mice deficient in insulin (and leptin), even though basal concentrations of glucose were similarly increased in the nonfasted normal and STZ-treated mice. Moreover, the basal rate of leptin influx was the same in overnight fasted normal mice, nonfasted normal mice and STZ-diabetic mice. The results indicate that glucose and insulin can increase leptin transport, but they probably are not the principal factors responsible for the regulatory effect of the BBB on leptin entry into the brain.
Expression of Corticotropin-Releasing Hormone Type 1 Receptor in Paraventricular Nucleus after Acute Stress
Authors: Imaki Toshihiro , Katsumata Harumi , Miyata Mariko , Naruse Mitsuhide , Imaki Junko , Minami Shiro
Published: April 2003

We have previously proposed the existence of ultrashort loop-positive feedback regulation of corticotropin-releasing hormone (CRH) in the hypothalamus. To gain a better understanding of this effect, we performed double-label in situ hybridization to identify the neurons in the paraventricular nucleus (PVN) that express CRH type 1 receptor (CRH-R1) following stress. We also conducted immunohistochemistry to determine whether CRH-R1 mRNA was translated to CRH-R1 protein in the PVN. Thirty-minute restraint stress given to male Wistar rats increased c-fos mRNA expression primarily in the CRH-producing neurons of the parvocellular PVN. Small numbers of vasopressin and oxytoxin-producing cells were also labeled by c-fos probes. Approximately 70% of CRH-R1 positive neurons exhibited CRH mRNA 2 h after the beginning of stress, while only a small percentage of the vasopressin and oxytocin-producing cells coexpressed CRH-R1 mRNA. CRH-R1 immunoreactivity, which was detected in the perikarya and fibers of PVN neurons, appeared to increase in response to stress, though this was not statistically significant. Pretreatment with a selective CRH-R1 antagonist, CP-154,526, significantly attenuated stress-induced corticotropin (ACTH) secretion as well as c-fos mRNA expression in the PVN. These results demonstrate that acute stress increases neuronal activation and CRH-R1 mRNA expression primarily in CRH-producing neurons of the parvocellular PVN, that CRH-R1 message is translated to CRH-R1 protein, and that PVN neurons are activated at least in part through CRH-R1 under acute stress. The data further support the possibility of feedback regulation of CRH itself in CRH-producing neurons.
Differential Effect of Serotonin 5-HT1A Receptor Antagonists on the Secretion of Corticotropin and Prolactin
Authors: Jørgensen Henrik , Kjær Andreas , Warberg Jørgen , Knigge Ulrich
Published: April 2003

Serotonin (5-HT) participates in the neuroendocrine regulation of corticotropin (ACTH) and prolactin (PRL) secretion. We investigated the involvement of the 5-HT1A receptor in the mediation of ACTH and PRL response to the 5-HT1A receptor agonists 8-OH-DPAT and 5-HT, the 5-HT precursor 5-hydroxytryptophan (5-HTP) and restraint stress in male rats. Prior intracerebroventricular (i.c.v.) infusion of the 5-HT1A antagonists WAY-100635 and LY-206130 inhibited PRL and ACTH responses to i.c.v. infusion of 8-OH-DPAT, 5-HT as well as to 5-HTP administered systemically in combination with the 5-HT reuptake inhibitor fluoxetine (Flx). Infused i.c.v. NAN-190 inhibited the ACTH response to 8-OH-DPAT i.c.v. Intraperitoneal (i.p.) pretreatment with WAY-100635 inhibited ACTH and PRL responses to 8-OH-DPAT, whereas LY-206130 only inhibited the PRL response and NAN-190 had no effect. Injected i.p., the antagonists had no effect on 5-HT-induced hormone secretion, whereas the ACTH-stimulating effect of 5-HTP + Flx was increased by WAY and NAN. A 5-min restraint stress increased ACTH and PRL secretion; the ACTH, but not the PRL response to stress was inhibited by prior administration of WAY-100635 or LY-206130 either i.c.v. or i.p. NAN-190 had no effect on any stress response tested. It is concluded that (1) the three 5-HT1A antagonists used in our study have differential effects on stimulated hormone responses, (2) the antagonists exert different effects when administered systemically or centrally, and (3) the 5-HT1A receptor is involved in restraint stress-induced ACTH, but not PRL secretion.
Release of Luteinizing Hormone from the Anterior Pituitary Gland in vitro Can Be Concurrently Regulated by at Least Three Peptides: Gonadotropin-Releasing Hormone, Oxytocin and Neuropeptide Y
Authors: Evans John J. , Pragg Fiona L. , Mason Drusilla R.
Published: April 2003

Normal action of the female ovulatory cycle is dependent on a surge of luteinizing hormone (LH) from the pituitary. Regulation of the levels of LH is therefore vital to reproductive function. It has long been established that gonadotropin-releasing hormone (GnRH) is an important component of the regulatory processes. Other peptides, including oxytocin and neuropeptide Y (NPY), have also been observed to affect LH activities. However, the possibility of the concurrent actions of these peptides has rarely been considered despite their documented presence in the hypophyseal blood during pro-oestrus. In this study, the direct effects of oxytocin and NPY on LH release were studied, as well as the effects of both peptides simultaneously. Also, pituitaries were stimulated with GnRH, and the effects of pre-exposure of the pituitary tissue to oxytocin or NPY were investigated. Further, the effect of oxytocin and NPY together on GnRH stimulation of LH release was determined. Anterior pituitaries were collected from adult female rats on the morning of pro-oestrus. Hemipituitaries were cut in two and placed in a chamber of a perifusion system. The pituitary tissue was perifused with medium alone, oxytocin and NPY, separately or in combination, for 2 h after an initial 100-min equilibration period with no peptide present. Fractions of eluate were collected and LH was measured by radioimmunoassay. LH output was stimulated by both oxytocin (p < 0.01) and NPY (p < 0.02). Furthermore, the addition of NPY to oxytocin during the perifusion elicited a further increase in LH release (p < 0.05). The pituitary tissue was exposed to a 4-min pulse of GnRH after 220 min. Stimulation of LH release by GnRH was synergistically augmented by exposure of the tissue to either oxytocin (p < 0.01) or NPY (p < 0.05) for the immediately preceding 2 h. When NPY was added to oxytocin in the perifusion medium, stimulation of LH release by GnRH was increased even further (p < 0.05). Oxytocin also synergistically enhanced the effect of a second, primed GnRH pulse, whereas the effect of NPY was less robust. This study therefore demonstrated that LH release is modified in the presence of oxytocin, NPY or GnRH alone, and also that combinations of the peptides produce further variations in LH output. Therefore, the concentrations of LH that are present in vivo are likely to be at least partly the result of the co-ordinated effects of combinations of peptides acting on the pituitary.
The Endocrine Disrupters Butyl Benzyl Phthalate and Bisphenol A Increase the Expression of Progesterone Receptor Messenger Ribonucleic Acid in the Preoptic Area of Adult Ovariectomized Rats
Authors: Funabashi Toshiya , Kawaguchi Maiko , Kimura Fukuko
Published: April 2003

Butyl benzyl phthalate (BBP) and bisphenol A (BPA), so-called endocrine disrupters, are known to mimic the action of estrogens: they are thus liable to influence reproductive functions. Since little is known about their action on gene expression in the adult hypothalamus, we examined the effects of these chemicals on the expression of estrogen-regulated mRNAs, i.e., progesterone receptor (PR) mRNA, preproenkephalin (PPE) mRNA and neurotensin (NT) mRNA, in the hypothalamus and pituitary of adult female rats. Two weeks after ovariectomy, rats were subcutaneously injected with 10 mg BBP, 10 mg BPA, or 10 µg 17β-estradiol (E2) in sesame oil, or with sesame oil alone as a control. Twenty-four hours after the injection, tissues including the preoptic area (POA), mediobasal hypothalamus (MBH) and anterior pituitary were collected. Northern blot revealed that injection of E2 resulted in expected changes, i.e., significant increases in PR mRNA in the POA, MBH and anterior pituitary, and in PPE mRNA in the MBH. We also found that injection of BPA significantly increased PR mRNA in the POA and anterior pituitary, while injection of BBP increased PR mRNA in the POA and anterior pituitary, although the increase in the anterior pituitary was not significant. No significant effect of E2, BPA, or BBP on NT mRNA in the POA was detected. The present study demonstrates that the two endocrine disrupters BPA and BBP can increase the expression of PR mRNA in the POA of adult ovariectomized rats.
Lack of Decrease in Hypothalamic and Hippocampal Glucocorticoid Receptor mRNA during Starvation
Authors: Makino Shinya , Kaneda Tadafumi , Nishiyama Mitsuru , Asaba Koichi , Hashimoto Kozo
Published: April 2003

We have shown in a previous study that high corticosterone levels during repeated immobilization stress result in a reduction of glucocorticoid receptor (GR) mRNA in the hypothalamic paraventricular nucleus (PVN) and the hippocampus. The reduction of GR presumably accounts for loss of or decrease in glucocorticoid-negative feedback, and thus hyperfunction of the hypothalamic-pituitary-adrenocortical (HPA) axis persists during chronic stress. Starvation is a stress state in which the counterregulatory responses against the loss of food occur in the central nervous system. We explored the impact of starvation on the HPA axis, GR and mineralocorticoid receptor (MR) mRNAs in the hippocampus, the PVN, and the anterior pituitary (AP) of rats. Rats were starved for 4 days and sacrificed in the morning. Starved rats showed high levels of plasma corticosterone, whereas neither plasma corticotropin (ACTH), AP proopiomelanocortin (POMC) mRNA nor AP type-1 corticotropin-releasing hormone (CRH) receptor mRNA was altered in the starved rats. In the presence of high corticosterone, starvation resulted in a decrease in both CRH mRNA and type-1 CRH receptor mRNA in the PVN. Consistently, the starved rats did not show any changes in GR mRNA in the hippocampus (CA1-2, CA3, and dentate gyrus), the PVN or the AP despite the elevation of plasma corticosterone. A significant decrease in MR mRNA was seen in the dentate gyrus and the AP, but not in CA1–2, CA3 or PVN. The lack of reduction of GR may be one of the organism’s counterregulatory responses during starvation, which allows an intact glucocorticoid negative feedback, thereby resulting in decreased anorectic neuropeptide levels, namely CRH, in the PVN. The results also indicate that GR mRNA in the hippocampus and other brain regions is not solely regulated by circulating glucocorticoids. The mechanism underlying the regulation of GR mRNA in the central nervous system remains to be clarified.
Central Stimulatory Influence of Oxytocin on Preovulatory Gonadotropin-Releasing Hormone Requires More than the Median Eminence
Authors: Selvage Daniel , Johnston Craig A.
Published: April 2003

The study was designed to determine whether the ability of central oxytocin (OT) to stimulate gonadotropin-releasing hormone (GnRH) on the afternoon of proestrus (PE) in the cycling female rat is mediated at the level of GnRH terminals within the median eminence (ME), or at higher hypothalamic levels where GnRH cell bodies and axons are located. Determining the location of this OT effect in vivo has proven difficult. Therefore, an in vitro system utilizing ME or basal hypothalamic (BH) explants containing GnRH terminals, or GnRH neurons including the cell bodies, axons and terminals, respectively, were harvested from regular cycling female rats at 15:00 h on PE or diestrus (DI). The explants were allowed to preincubate in Krebs Ringer Bicarbonate Buffer containing glucose, ascorbic acid, calcium, and a metalloprotease inhibitor (KRBG) and enriched with 95% O2/5% CO2 at 37°C until a stable baseline release of GnRH was achieved (30 min). The 0.05 level of probability was used as the minimum criterion of significance in all experiments. The ability of OT (10–15–10–9M) to stimulate the release of GnRH was determined in both ME and BH explants on PE and DI. The results demonstrated a sensitive, dose-dependent ability of OT to stimulate GnRH release from PE BH explants which was observed only in PE. Furthermore, OT failed to significantly stimulate GnRH release from ME explants on either PE or DI. The data indicate that the PE BH explant paradigm can be used to examine the manner and mechanisms by which OT influences GnRH release on the afternoon of PE. Furthermore, the results indicate for the first time that the stimulatory action of OT by itself on preovulatory GnRH release in cycling female rats is not mediated at the level of the GnRH terminals within the ME, but requires neuronal interactions and mechanisms within the BH explants.
Acute Effects of Purified and UV-Inactivated Herpes simplex Virus Type 1 on the Hypothalamo-Pituitary-Adrenocortical Axis
Authors: Ben-Hur Tamir , Cialic Ron , Itzik Anna , Yirmiya Raz , Weidenfeld Joseph
Published: April 2003

Herpes simplex virus type 1 (HSV-1) is a common cause of viral encephalitis, manifested by neuroendocrine and behavioral changes. We have previously demonstrated that HSV-1 induces marked hypothalamo-pituitary-adrenocortical (HPA) axis activation. In this study we characterized the acute effects of HSV-1 on the HPA axis occurring before viral replication and appearance of clinical signs of encephalitis. Since in previous studies we used crude virus preparations which may contain immune factors produced by the infected cells, we tested here the effects of purified HSV-1 virions. HSV-1 was propagated on Vero cells and virions were purified by centrifugation in sucrose gradients. Inactivation of viral infectivity was achieved by UV-irradiation, which caused a million-fold decrease in virus titer, as determined by plaque assay. Intracerebroventricular (ICV) inoculation of crude or purified virions induced a dose dependent increase in serum corticosterone and corticotropin (ACTH). This effect was maximal within 3.5 h postinfection and lasted for 72 h. ICV inoculation of UV-inactivated purified virions caused a marked increase in serum corticosterone and ACTH at 3.5 h, but in contrast to the effect of the active virus, the hormone levels gradually decreased at 24 h, and returned to basal levels at 72 h postinfection. HSV-1-induced HPA axis activation at 3.5 h was completely abolished by pretreatment with interleukin-1 receptor antagonist, injected ICV. Adrenalectomized rats failed to respond to ICV inoculation of purified HSV-1 by increase in ACTH. In contrast, these rats responded to ICV injection of LPS. In conclusion: (1) HSV-1 can acutely activate the HPA axis before and independently of any viral replication; (2) HSV-1-induced HPA axis activation depends on a permissive action of circulating glucocorticoids and on host derived brain interleukin-1.
Role of Gonadal Steroids in the Corticotropin-Releasing Hormone and Proopiomelanocortin Gene Expression Response to Δ9-Tetrahydrocannabinol in the Hypothalamus of the Rat
Authors: Corchero Javier , Manzanares Jorge , Fuentes José A.
Published: April 2003

Chronic exposure to Δ9-tetrahydrocannabinol (Δ9-THC) increases corticotropin-releasing hormone (CRH) and proopiomelanocortin (POMC) gene expression in the rat hypothalamus. The levels of circulating gonadal steroids concurrently modulate both neuropeptides in male and female rats. However, it remains unknown whether gonadal steroids regulate Δ9-THC effects on CRH and POMC gene expression in the hypothalamus of male and female rats. To explore this hypothesis, experiments were conducted on intact, 2-week-gonadectomized, 1-week-gonadectomized, 1-week-dihydrotestosterone (DHT)- or estradiol-replaced male and female rats. One week after hormonal replacement, animals were treated with vehicle or Δ9-THC (5 mg/kg/day, i.p. for 7 days). Administration of Δ9-THC to intact male rats increased CRH gene expression. Castration abolished Δ9-THC effects of CRH gene expression in males but not in females. On the other hand, POMC mRNA levels were reduced as a result of castration, and DHT treatment did not prevent this decrease. Δ9-THC treatment similarly increases POMC gene expression of intact, orchidectomized and DHT-replaced males. In females, ovariectomy decreased CRH gene expression. Δ9-THC administration increased CRH gene expression to the same extent in castrated and estradiol-replaced rats. On the other hand, POMC gene expression was increased by ovariectomy, and Δ9-THC administration did only increase POMC transcript levels in the estradiol-replaced group. These data show that gonadal steroids differentially regulate the effects of Δ9-THC on both CRH and POMC gene expression in the hypothalamus of male and female rats, suggesting gender differences in the reaction to cannabinoids.
Differential Expression of Calcium Channel Subtypes in the Bovine Adrenal Medulla
Authors: García-Palomero Esther , Renart Jaime , Andrés-Mateos Eva , Solís-Garrido Luisa M. , Matute Carlos , Herrero Carlos J. , García Antonio G. , Montiel Carmen
Published: April 2003

This study aimed at determining the distribution and expression levels of different subtypes of Ca2+ channels in the bovine adrenal medulla, and whether individual subtypes were more abundant in chromaffin cells exhibiting an adrenergic or a noradrenergic phenotype. In situ hybridization using riboprobes specific for the pore-forming Ca2+ channel α1D (L-type channel), α1B (N-type channel), and α1A (P/Q-type channel) subunits of bovine chromaffin cells showed a broad distribution of the three transcripts in adrenal medulla tissue. However, a tissue-specific expression pattern of individual subunits was found; whereas α1B mRNA was homogeneously distributed throughout the medulla, α1D and α1A transcripts were present at higher densities in the internal medullary area, far away from the adrenal cortex. These results were corroborated by comparative analysis of the α1B, α1D, and α1A products amplified by RT-PCR from total RNA extracted from small pieces of tissue dissected out from external or internal medullary areas. Interestingly, immunohistochemical experiments performed in adrenal gland sections, using antidopamine-β-hydroxylase and anti-phenylethanolamine-N-methyltransferase antibodies, indicated a higher density of noradrenergic over adrenergic chromaffin cells in the internal medullary region. These results provide direct evidence in favor of a heterogeneous distribution of Ca2+ channel subtypes in the adrenal medulla, in agreement with previous functional data showing that blockade of the high K+-elicited responses by dihydropyridines was greater in noradrenergic than in adrenergic chromaffin cells. These differences may be relevant for the differential release regulation of each catecholamine under physiological and pathophysiological conditions.
Estradiol and para-Chlorophenylalanine Downregulate the Expression of Brain Aromatase and Estrogen Receptor-α mRNA during the Critical Period of Feminization in Tilapia (Oreochromis mossambicus)
Authors: Tsai Ching-Lin , Wang Li-Hsueh , Fang Lee-Shing
Published: April 2003

The period of maximal feminizing action of 17β-estradiol (E2) upon sex ratio is before 10 days posthatching in tilapia (Oreochromis mossambicus). The effect of E2 at this time is mimicked by para-chlorophenylalanine (p-CPA), a serotonin (5-hydroxytryptamine; 5-HT) synthesis inhibitor. The effect of E2 on sexual differentiation may be mediated by the 5-HT system, which is consistent with the suggestion in mammals. The masculinizing actions of 17α-methyltestosterone (MT) are most potent later at up to day 20 of age, and may depend on MT induction of aromatase activity. In the present study, the effects of gonadal steroids and p-CPA on brain aromatase and estrogen receptor (ER) mRNA expression during the critical period of sexual differentiation were investigated. Treatment of tilapia with E2 resulted in a significant decrease in the expression of brain aromatase and ERα between days 0 and 10, but not subsequently. The effect of E2 at this time can be mimicked by p-CPA. Treatment of tilapia with MT, by contrast, resulted in a significant increase in brain aromatase, ERα and ERβ mRNA expression when given between days 10 and 20. The downregulation of brain aromatase and ERα mRNA expression by E2 before 10 days of age and, in turn, the upregulation of brain aromatase and ERα and ERβ mRNA expression by MT at up to day 20 of age coincide with the period in which E2 and MT have the maximal effect on gonadal feminization and masculinization, respectively.
Mutation in the Neural Cell Adhesion Molecule Interferes with the Differentiation of Anterior Pituitary Secretory Cells
Authors: Gubkina Olena , Cremer Harold , Rougon Geneviève
Published: April 2003

The neural cell adhesion molecule (NCAM) and its polysialylated isoform (PSA-NCAM) have been shown to influence the proliferation, differentiation and survival of different cell types. Here, we report the pattern of expression of NCAM and PSA-NCAM in the anterior lobe (AL) of the pituitary gland of the adult mouse. We demonstrate that the majority of cells express NCAM, while PSA-NCAM is retained mostly on corticotropes. Analysis of bromodeoxyuridine (BrdU) incorporation shows that the presence of PSA-NCAM on corticotropes is not related to proliferation but most likely to their functional properties. We subsequently analyzed defects induced by NCAM deficiency in adult NCAM knockout mice. In these mice, all secretory cell types in the AL are present and their distribution within the gland is similar to that in wild-type mice. However, proliferation of AL cells is significantly increased. In particular, more BrdU-positive cells are detected among somatotropes and mammotropes in NCAM-deficient mice. In addition, the percentages of secretory cells are changed: somatotropes are more numerous while the number of corticotropes is reduced. These data demonstrate the involvement of NCAM in the proper generation and/or maintenance of the different cell populations in the AL and suggest the importance of PSA in corticotrope functioning.
Changes in Fos Expression in Various Brain Regions during Deoxycorticosterone Acetate Treatment: Relation to Salt Appetite, Vasopressin mRNA and the Mineralocorticoid Receptor
Authors: Pietranera Luciana , Saravia Flavia E. , McEwen Bruce S. , Lucas Louis L. , Johnson Alan Kim , De Nicola Alejandro F.
Published: April 2003

Salt appetite, a conditioning factor for hypertension and cardiovascular diseases, is produced when high doses of mineralocorticoids are given to experimental animals. A commonly used procedure to identify neuronal activation is to determine the number of Fos-immunoreactive cells. In rats with established salt appetite after 8 days of deoxycorticosterone acetate (DOCA) treatment, Fos-positive cells were studied in seven brain areas. Significant increases in Fos activity were recorded in the paraventricular (PVN) and supraoptic (SON) nuclei, median preoptic nucleus (MnPO), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA), bed nucleus of the stria terminalis (BNST) and amygdala (AMYG). In most of these areas, increased Fos expression was also observed early (2 h) after a single DOCA injection, well before salt appetite develops. Using a mineralocorticoid receptor (MR) antibody, we studied whether Fos-active regions also expressed MR. MR-positive cells were found in the OVLT, MnPO, AMYG and BNST, but not in the POA, PVN and SON. In the PVN and SON, nevertheless, prolonged or single DOCA treatment increased expression of mRNA for arginine vasopressin (AVP). The present demonstration of Fos activation, in conjunction with differential expression of MR and stimulation of AVP mRNA, suggests that a neuroanatomical pathway comprising the AMYG, osmosensitive brain regions and magnocellular nuclei becomes activated during DOCA effects on salt appetite. It is recognized, however, that DOCA effects may also depend on mechanisms and brain structures other than those considered in the present investigation. Since some Fos-positive regions were devoid of MR, a comprehensive view of DOCA-induced salt appetite should consider nongenomic pathways of steroid action, including the role of reduced DOC metabolites binding to GABAergic membrane receptors.
The Hypothalamic Melanocortin System Stimulates the Hypothalamo-Pituitary-Adrenal Axis in vitro and in vivo in Male Rats
Authors: Dhillo Waljit S. , Small Caroline J. , Seal Leighton J. , Kim Min-Seon , Stanley Sarah A. , Murphy Kevin G. , Ghatei Mohammed A. , Bloom Stephen R.
Published: April 2003

α-Melanocyte-stimulating hormone (α-MSH) is an agonist, and agouti-related protein (Agrp) an endogenous antagonist at the melanocortin 3 and 4 receptors which are found in the central nervous system (CNS). We have examined the effect of α-MSH and Agrp on the hypothalamo-pituitary-adrenal (HPA) axis in vitro and in vivo in male rats. Intraparaventricular nuclear (iPVN) injection of [Nle4,D-Phe7]-α-MSH (NDP-MSH) (a long-acting α-MSH analogue) increased plasma adrenocorticotropic hormone (ACTH) (10 min post-injection: 25.0 ± 3.9 vs. saline 10.9 ± 2.0, p < 0.05) and plasma corticosterone (10 min post-injection: 174.1 ± 14.2 vs. saline 124.7 ± 16.3 ng/ml, p < 0.05). iPVN injection of Agrp(83–132) increased plasma ACTH (24.2 ± 4.0 vs. saline 10.1 ± 1.0 pg/ml, p < 0.01). The combination of NDP-MSH and Agrp(83–132) administered iPVN significantly increased plasma ACTH (10 min post-injection: 21.3 ± 3.8 vs. 10.9 ± 2.0, p < 0.05) and plasma corticosterone (10 min post-injection: 169.0 ± 15.1 vs. saline 124.7 ± 16.3 ng/ml, p < 0.05), but there was no additive effect. Hypothalamic explants treated with α-MSH (100 nM) resulted in a 159 ± 23% increase in corticotropin-releasing hormone (CRH) release (p < 0.01) and 175 ± 12% increase in arginine vasopressin (AVP) release (p < 0.001) compared to basal. Agrp(83–132) (100 nM) administered to hypothalamic explants resulted in a 161 ± 20% increase in CRH (p < 0.01) and 174 ± 13% increase in AVP release (p < 0.001) compared to basal. Hypothalamic explants treated with the combination of α-MSH and Agrp(83–132) (100 nM) resulted in a 179 ± 31% increase in CRH release (p < 0.01) and 130 ± 9% increase in AVP release (p < 0.01) compared to basal, but there was no additive effect. This is the first report that both α-MSH and Agrp(83–132) stimulate the HPA axis. The combination of α-MSH and Agrp(83–132) has no additive effect in vitro and in vivo in male rats. These results suggest that there may be another receptor independent of the known melanocortin receptors at which Agrp is acting.
Plasma Leptin Levels Are Pulsatile in Adult Rats: Effects of Gonadectomy
Authors: Bagnasco Michela , Kalra Pushpa S. , Kalra Satya P.
Published: April 2003

Leptin, primarily secreted by adipocytes, is a peripheral hormonal signal involved in the hypothalamic integration of energy homeostasis. We report that plasma leptin levels fluctuated in a pulsatile fashion in gonad-intact adult female and male rats. Whereas in male rats leptin was secreted in the form of low-amplitude, high-frequency pulses, in female rats high-amplitude pulses were secreted at only a slightly lower frequency. Consequently, plasma leptin concentrations were higher in female than in male rats. Gonadectomy decreased leptin secretion but the sexually dimorphic leptin pulsatility pattern persisted. These results show that there is a distinct female-type and male-type leptin pulsatility pattern and each is amenable to augmentation by gonadal steroids either involving mechanisms that impart leptin pulsatility patterns directly at the level of adipocytes and/or at hypothalamic target sites.
Association between Blood Pressure and Cognitive Function in a Biracial Community Population of Older Persons
Authors: Morris Martha Clare , Scherr Paul A. , Hebert Liesi E. , Bennett David A. , Wilson Robert S. , Glynn Robert J. , Evans Denis A.
Published: April 2003

We examined whether or not blood pressure is related to cognitive function in a cross-sectional study of a biracial community of 5,816 persons aged 65 years and older. Blood pressure had a curvilinear association with cognitive performance in linear regression models adjusted for age, sex, race and education. Scores were lower by 2–5 percentiles at 100 mm Hg systolic pressure compared to scores at the mean of 140 mm Hg and lower by <1 percentile at 180 mm Hg. For diastolic pressure, scores were lower by 2–3 percentiles at 60 mm Hg and by 1–2 percentiles at 100 mm Hg compared to scores at the mean (77 mm Hg). The differences in the scores with low blood pressure were reduced with further adjustment for body mass index, self-perceived health status, depressive symptoms, alcohol use and smoking. The curvilinear associations were stronger among persons with histories of stroke, myocardial infarction and hypertension. The cross-sectional association between blood pressure and cognitive functions is small and curvilinear and more apparent in persons with cardiovascular conditions.
Stroke Mortality in Andalusia (Spain) from 1975 to 1999: Effect of Age, Birth Cohort and Period of Death
Authors: Cayuela Aurelio , Rodríguez Susana , Iglesias Pablo , Lapetra José , Gil-Peralta Alberto
Published: April 2003

The aim of this study was to analyze stroke mortality rates in Andalusia during the period from 1975 to 1999 by studying age, cohort and period effects. Deaths due to stroke along with the corresponding population figures were divided into 11 age groups and five 5-year periods. From this, age-specific mortality rates for 15 birth cohorts were then computed. These were plotted and fitted to Poisson regression models to assess age, period and cohort effects. An exponential age effect was present for both sexes regardless of cohort or period. The rates of stroke mortality decreased significantly among both sexes in Andalusia during the study period, although in recent years, this declining trend has started to slow down, primarily in males. Age- and period-adjusted stroke mortality was greater for earlier cohorts and lower for generations born at the beginning of the 20th century.
Der Einfluss von druckinduzierten Trommelfellbewegungen auf vestibulospinale und vestibulookuläre Reaktionen bei Patienten mit Morbus Ménière
Authors: Petzold T. , Hüttenbrink K.-B. , Dörr Chr.
Published: April 2003

Fragestellung: Mögliche Interaktionen zwischen Mittelohrdruck und Gleichgewichtsstörungen werden seit vielen Jahren diskutiert. Der Rolle der druckausgelösten Trommelfellbewegungen, die bei degenerativ fixierten Ossikelgelenken aufgrund des Hydraulikfaktors eine viel grössere Kraft ausüben als der direkte Druck an den Innenohrfenstern, wurde dabei nur geringe Aufmerksamkeit gewidmet. Patienten und Methodik: Wir untersuchten bei 19 Patienten mit einseitigem Morbus Ménière die durch wechselnde Drucke im äusseren Gehörgang (analog zur Tympanometrie) ausgelösten Interaktionen zwischen Trommelfellauslenkungen und vestibulären Reaktionen in der Elektronystagmographie und in der Posturographie. Ergebnisse und Schlussfolgerungen: Bei schnellen und langsamen Druckwechseln konnten zwischen –600 und +400 daPa weder auf dem gesunden noch auf dem erkrankten Ohr im Elektronystagmogramm Nystagmen nachgewiesen werden. Die posturographische Aufzeichnung der vestibulospinalen Reaktionen auf einer Luzerner Messplatte erwies sich dagegen als sensibler. Die Längenzunahme der Schwankungslinie zeigte bei beiden durchgeführten Druckwechseln auf dem kranken Ohr signifikante Unterschiede gegenüber der Messung bei Reizung des gesunden Ohres. Diese Methode ist somit der klassischen Prüfung des Hennebertschen Fistelsymptoms überlegen. Das vestibulospinale System reagiert möglicherweise empfindlicher als das vestibulookuläre auf Druckschwankungen der Perilymphe. Darüber hinaus könnte der nachgewiesene Zusammenhang der druckausgelösten Trommelfellbewegungen mit cochleovestibulären Symptomen bei einigen Patienten mit M. Ménière den Erfolg einer Paukenröhrcheneinlage erklären, da hiermit aussendruckinduzierte Trommelfellbewegungen und damit verbundene Perilymphschwankungen von vornherein unterbunden werden.