bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Sensitivity to ACTH, but Not Stress, in Two Sources of Outbred Sprague-Dawley Rats
Authors: Matthys Laura , Castello Rosa , Zilz Alexandra , Widmaier Eric P. 
Published: April 2003

Adrenocorticotropic hormone (ACTH) is the major regulator of adrenocortical steroidogenesis in mammals. By comparing the sensitivity to ACTH of isolated adrenocortical cells from two sources of the same strain (Sprague-Dawley, SD) of outbred rats, we have identified a source of rat with low sensitivity to ACTH in vitro. Cells isolated from Holtzman SD rats had a high sensitivity to ACTH (minimal effective concentration 50 pg/ml), whereas Taconic SD rats had a low sensitivity (minimal effective concentration 250 pg/ml; maximal steroidogenesis <50% of Holtzman cells). The responsiveness to analogues of cyclic adenosine monophosphate and cholesterol was also significantly lower in Taconic SD rats. Taconic adrenals were smaller, had significantly more mitochondria per cell, but approximately 20% less total lipid droplet volume per cell. There was no difference in latency to ACTH in vitro; however, steroidogenesis plateaued in Taconic cells after 25 min, while Holtzman cells secreted corticosterone almost linearly for at least 120 min. By contrast, the cyclic adenosine monophosphate secretion increased at the same rate for at least 120 min in cells from both sources. There were no differences between cells from the two sources in immunoreactive steroidogenic enzyme content. In vivo, the magnitude of the ACTH and corticosterone responses to two types of stress were similar in both sources. The thymus glands of Holtzman rats were significantly larger than those of Taconic rats. It is concluded that: (1) reduced sensitivity to ACTH in vitro in Taconic SD rats results from differences in the later stages of the steroidogenic pathway; (2) factors in addition to ACTH are required for maximal steroidogenesis in Taconic SD rats; (3) a comparison of the steroidogenic pathways in adrenal cells from these two sources of outbred rats should be useful in further delineating the relative importance of putative intracellular signalling mechanisms involved in initiation and maintenance of steroidogenesis, and (4) these data suggest that different sources of the same strain of rats sufficiently diverge over time to become separate strains (‘substrains’). Overreliance on a single source of laboratory rodent may obscure natural variability in endocrine responses to stress and provide a misleading indication of homogeneity of responses.
Unexpected Activation of Pituitary-Adrenal Axis in Healthy Young and Elderly Subjects during Somatostatin Infusion
Authors: Ambrosio Maria R. , Campo Michela , Zatelli Maria C. , Cella Silvano G. , Trasforini Giorgio , Margutti Angelo , Rigamonti Antonello E. , Müller Eugenio E. , degli Uberti Ettore C. 
Published: April 2003

In this study we explored, in man, the effect of acute attenuation of growth hormone (GH) release induced by somatostatin (SRIH) on ACTH and cortisol plasma levels. Sixteen young (8 women, aged 23–32 years, and 8 men, aged 18–27 years) and 14 elderly (8 women, aged 65–82 years, and 6 men, aged 65–70 years) healthy subjects volunteered to participate in this investigation. Each subject was tested on two separate occasions by: (1) a 90-min i.v. infusion of SRIH given in 50 ml 0.9% saline delivered at a rate of 9 µg/kg/h, and (2) a 90-min i.v. infusion of isovolumetric amounts of 0.9% saline. Plasma GH, ACTH, cortisol and glucose concentrations were determined prior and up to 180 min after SRIH or saline infusion. SRIH induced a significant (p < 0.05) decrease in plasma GH levels from basal values of 0.6 ± 0.15 and 0.5 ± 0.15 µg/l to nadir values 0.25 ± 0.1 and 0.2 ± 0.1 µg/l in young and elderly subjects, respectively. The administration of SRIH was associated with a clear-cut increase in plasma ACTH levels both in young (peak, 10.6 ± 1.6 pmol/l; AUC, 558.6 ± 147.5 pmol/l/h) and in elderly (peak, 21.3 ± 5.6 pmol/l; AUC, 841.9 ± 153.8 pmol/l/h) subjects with a significant (p < 0.01) difference as compared to saline infusion. Consistent with these results, SRIH infusion resulted in an unequivocal rise in plasma cortisol levels both in young (peak, 394.8 ± 36.4 nmol/l; AUC, 18,591.62 ± 1,372.45 nmol/l/h) and in elderly (peak, 585.6 ± 51.5 nmol/l; AUC, 24,871.05 ± 1,837.03 nmol/l/h) subjects. The ACTH and cortisol responses to SRIH were significantly (p < 0.05 and p < 0.01) higher in elderly than in young subjects. No sex-related differences occurred in the SRIH-induced activation of hypothalamic-pituitary-adrenocortical (HPA) axis. We conclude that (1) infusion of SRIH, at a dose that inhibited basal GH secretion, was associated with an activation of HPA axis, and (2) this response was higher in elderly individuals compared with younger adults. The reason for this novel and unexpected SRIH effect is presently unclear; however, the latter may be mediated, at least in part, by some central nervous system ACTH-releasing mechanisms activated by SRIH-induced decrease in GH secretion.
D<sub>2</sub> Dopamine-Receptor-Mediated Inhibition of Proliferation of Rat Lactotropes in Culture Is Accompanied by Changes in Cell Shape
Authors: Arita Jun , Hashi Akihiko , Hoshi Kazuhiko , Mazawa Sachiko , Suzuki Shinichi 
Published: April 2003

Dopaminergic agonists are effective in vivo in inhibiting lactotrope proliferation and prolactin (PRL)-secreting pituitary tumors. The purpose of the present study was to demonstrate in vitro actions of dopaminergic agents on proliferation and cell shape of rat lactotropes. Anterior pituitary cells cultured with serum-free, chemically defined medium were treated with dopaminergic agents and were labeled with 5-bromo-2′-deoxyuridine (BrdU) for 3 h before the end of culture. BrdU-labeling indices indicative of the proliferation rate of lactotropes were determined by double immunofluorescence staining for BrdU and PRL. Treatment with dopamine for 21 h decreased BrdU-labeling indices of lactotropes in a dose-dependent manner with a nadir at 3 × 10<sup>–7</sup> <i>M</i>. The inhibitory action of 10<sup>–5</sup> <i>M</i> dopamine appeared 15 h after the initiation of treatment and became pronounced with time up to 33 h. The dopamine action was mimicked by treatment with the D<sub>2</sub> receptor agonist bromocriptine at concentrations over 10<sup>–9</sup> <i>M</i>. Phase-contrast microscopy revealed that the flat polygonal cell shape of cultured lactotropes had changed to a round refractive cell shape after treatment with dopamine or bromocriptine, and that these changes in cell shape exactly paralleled those in the BrdU-labeling index. The changes in cell shape of lactotropes were accompanied by changes in subcellular distribution of actin filaments. Pretreatment with 10<sup>–7</sup> <i>M</i> eticlopride, a D<sub>2</sub> receptor antagonist, blocked the dopamine- or bromocriptine-induced changes in both BrdU-labeling index and cell shape. These results suggest that (1) the in vitro experimental system established in the present study is a good model for studying the mechanism of the antiproliferative action of dopamine and (2) D<sub>2</sub>-receptor-mediated inhibition of proliferation of lactotropes in serum-free culture is closely related to changes in actin organization and cell shape.
Dexamethasone Rapidly Regulates TRH mRNA Levels in Hypothalamic Cell Cultures: Interaction with the cAMP Pathway
Authors: Pérez-Martínez Leonor , Carreón-Rodríguez Alfonso , González-Alzati Ma. Elena , Morales Claudia , Charli Jean Louis , Joseph-Bravo Patricia 
Published: April 2003

The biosynthesis of thyrotropin-releasing hormone (TRH) in the hypothalamic paraventricular nucleus (PVN) is subject to neural and hormonal regulations. To identify some of the potential effectors of this modulation, we incubated hypothalamic dispersed cells with dexamethasone for short periods of time (1–3 h) and studied the interaction of this hormone with protein kinase C (PKC) and PKA signaling pathways. TRH mRNA relative changes were determined by the RT-PCR technique. One hour incubation with 10<sup>–10</sup>–10<sup>–4</sup> <i>M</i> dexamethasone produced a concentration-dependent biphasic effect: an inhibition was observed on TRH mRNA levels at 10<sup>–10</sup><i>M</i>, an increase above control at 10<sup>–8</sup>–10<sup>–6</sup><i>M</i> and a reduction at higher concentrations (10<sup>–5</sup>– 10<sup>–4</sup><i>M</i>). The stimulatory effect of 10<sup>–8</sup><i>M</i> dexamethasone on TRH mRNA was essentially independent of new protein synthesis, as evidenced by cycloheximide pretreatment. Changes in TRH mRNA levels were reflected by enhanced TRH cell content. Incubation with a cAMP analogue (8-bromo-cAMP, 8Br-cAMP) or with a PKC activator (12-<i>O</i>-tetradecanoylphorbol-13-acetate, TPA) increased TRH mRNA levels after 1 and 2 h, respectively. An increase in TRH mRNA expression was observed by in situ hybridization of dexamethasone or 8Br-cAMP-treated cells. The interaction of dexamethasone, PKA and PKC signaling pathways was studied by combined treatment. The stimulatory effect of 10<sup>–7</sup><i>M</i> TPA on TRH mRNA levels was additive to that of dexamethasone; in contrast, coincubation with 10<sup>–3</sup><i>M</i> 8-Br-cAMP and dexamethasone diminished the stimulatory effect of both drugs. An inhibition was observed when the cAMP analogue was coincubated with TPA or TPA and dexamethasone. These results demonstrate that dexamethasone can rapidly regulate TRH biosynthesis and suggest a cross talk between cAMP, glucocorticoid receptors and PKC transducing pathways.
Corticotropin-Releasing Effect of Hexarelin, a Peptidyl GH Secretagogue, in Normal Subjects Pretreated with Metyrapone or RU-486, a Glucocorticoid Receptor Antagonist, and in Patients with Addison’s Disease
Authors: Arvat Emanuela , Ramunni Josefina , Maccagno Barbara , Giordano Roberta , Broglio Fabio , Deghenghi Romano , Boscaro Marco , Ghigo Ezio 
Published: April 2003

GH secretagogues (GHS) are peptidyl and nonpeptidyl molecules which possess strong GH-releasing activity but also stimulatory effect on hypothalamo-pituitary-adrenal axis. The ACTH and cortisol responses to Hexarelin (HEX), a peptidyl GHS, are abolished by low-dose dexamethasone pretreatment in normal subjects but are exaggerated and higher than those after hCRH in patients with pituitary ACTH-dependent Cushing’s disease, in spite of their hypercortisolism. Based on the foregoing, we studied the ACTH, cortisol and GH responses to HEX (2.0 µg/kg i.v. at 0 min) alone and after metyrapone (2 g p.o. at 23:00 h the night before) or RU-486 (400 mg p.o. at 02:00 h), a glucocorticoid receptor antagonist, in 6 normal women (NS, age 26–34 years). The endocrine responses (mean ± SEM) to HEX alone were also studied in 8 patients with Addison’s disease (AD, 6 males, 2 females, age 30–77 years; last hydrocortisone administration the day before testing). In NS, HEX stimulated basal ACTH (peak, mean ± SEM: 26.0 ± 7.8 vs. 10.7 ± 2.0 pg/ml, p < 0.05), cortisol (163.2 ± 18.3 vs. 137.4 ± 15.4 µg/l, p < 0.05) and GH (72.6 ± 23.5 vs. 3.7 ± 1.3 µg/l, p < 0.01) levels. Metyrapone markedly increased basal ACTH (294.4 ± 61.6 pg/ml, p < 0.05), reduced basal cortisol (19.6 ± 7.2 µg/l, p < 0.05), while it did not modify GH levels. After metyrapone pretreatment the ACTH response to HEX was clearly increased (ΔAUC: 2,857.4 ± 901.9 vs. 367.3 ± 274.0 pg/ml/h, p < 0.05), while the GH response was not modified. HEX did not stimulate the low cortisol levels after metyrapone pretreatment. RU-486 significantly increased basal ACTH (76.6 ± 12.5 pg/ml, p < 0.05) and cortisol (312.7 ± 22.2 µg/l, p < 0.05), while it did not modify basal GH levels. RU-486 pretreatment did not modify the ACTH, cortisol and GH responses to HEX. In AD, HEX elicited a marked ACTH response (6,619.4 ± 3,365.8 pg/ml/h; p < 0.01), which was clearly higher (p < 0.01) than that in NS after HEX alone but not significantly different from that after HEX+MET. The GH response to HEX in AD (1,325.6 ± 284.1 µg/l/h) was similar to that in NS (1,519.7 ± 483.8 µg/l/h). In conclusion, our present data demonstrate that the ACTH-releasing activity of HEX is increased in primary hypoadrenalism as well as in normal subjects after metyrapone but not after RU-486 pretreatment. These findings indicate that in normal subjects as well as in hypocortisolemic patients the ACTH-releasing activity of GHS is enhanced by the lack of negative glucocorticoid feedback.
Leptin<sub>116–130</sub> Stimulates Prolactin and Luteinizing Hormone Secretion in Fasted Adult Male Rats
Authors: Gonzalez Lucas C. , Pinilla Leonor , Tena-Sempere Manuel , Aguilar Enrique 
Published: April 2003

Leptin is a hormone secreted by adipocytes with an important role in the control of feeding behavior and neuroendocrine function. Leptin stimulates in vivo LH secretion in fasted female rats and in vitro PRL secretion. Recent data indicate that leptin<sub>116–130</sub>, an active fragment of the native molecule, exerts effects similar to those of the native peptide on body weight and food intake. The present study was carried out to determine whether this fragment is also able to stimulate LH and PRL secretion. Adult male rats fasted for 5 days were injected with saline or leptin<sub>116–130</sub> (15 µg i.c.v.) and LH and PRL concentrations were measured thereafter at 15-min intervals during a 150-min period. Administration of leptin<sub>116–130</sub> increased the frequency of LH pulses (2.0 ± 0.26 vs. 1.20 ± 0.37/150 min; p ≤ 0.05), mean LH levels (0.24 ± 0.06 vs. 0.07 ± 0.03 ng/ml; p ≤ 0.05), LH pulse amplitude (0.33 ± 0.10 vs. 0.10 ± 0.05 ng/ml; p ≤ 0.05) and the net LH secretion estimated by area under curve (AUC: 36 ± 8.5 vs. 9 ± 3.9 ng/ml/150 min; p ≤ 0.01). In addition leptin<sub>116–130</sub> increased the frequency of PRL pulses (2.83 ± 0.48 vs. 1.33 ± 0.21/150 min; p ≤ 0.05), trough PRL levels (5.71 ± 0.99 vs. 2.72 ± 0.32 ng/ml; p ≤ 0.01), mean PRL levels (13.02 ± 0.92 vs. 5.89 ± 0.51 ng/ml; p ≤ 0.01) and net PRL secretion (AUC: 1,625 ± 171 vs. 658 ± 46 ng/ml/150 min; p ≤ 0.05). In conclusion, these data show that leptin<sub>116–130</sub> stimulates LH and PRL secretion in fasted adult male rats.
Galanin’s Functional Significance in the Regulation of the Neuroendocrine Reproductive Axis of the Monkey
Authors: Finn Patricia D. , Pau K.-Y. Francis , Spies Harold G. , Cunningham Matthew J. , Clifton Donald K. , Steiner Robert A. 
Published: April 2003

Galanin stimulates the neuroendocrine reproductive axis in the rat, but whether galanin acts similarly in primate species is unknown. To test the hypothesis that galanin acts within the hypothalamo-hypophyseal axis to stimulate luteinizing hormone (LH) and gonadotropin-releasing hormone (GnRH) secretion in the primate, galanin was administered either systemically or directly into the arcuate nucleus-median eminence of ovariectomized macaques (pigtailed or rhesus, respectively) that were maintained on estradiol. The mean plasma levels of LH were significantly elevated in pigtailed macaques after peripheral injection of galanin (2 mg) as compared with vehicle treatment. In rhesus monkeys, galanin (80 µ<i>M</i>) administered by push-pull perfusion into the arcuate nucleus-median eminence did not significantly alter either GnRH or LH release. To determine whether in the monkey, as in the rat, subpopulations of medial forebrain GnRH neurons coexpress galanin mRNA, we used single- and double-label in situ hybridization and computerized imaging techniques. GnRH mRNA-containing cells were identified in both the medial and lateral forebrain of the female pigtailed macaque. No galanin mRNA expression was detectable in GnRH neurons located in either the medial preoptic area or mediobasal hypothalamus; however, within the substantia innominata a subset of GnRH mRNA-expressing neurons did coexpress galanin mRNA. Taken together, these results suggest that galanin induces LH release in primates, but galanin may not act directly on hypothalamic GnRH neurons. Presently, we have confirmed in another primate species the existence of GnRH gene expression in the lateral forebrain and discovered that a small subset of these neurons coexpress galanin. These particular cells may have a unique and as of yet undefined physiological function that is distinct from those GnRH neurons serving a hypophysiotropic function.
Acute Effects of Estradiol Pretreatment on the Response to <i>d</i>-Amphetamine in Women
Authors: Justice Angela J.H. , de Wit Harriet 
Published: April 2003

Little is known about the interactions between ovarian hormones and responses to psychoactive drugs in humans. Preclinical studies suggest that ovarian hormones such as estrogen and progesterone have direct and indirect central nervous system actions and that these hormones can influence behavioral responses to psychoactive drugs. In the present study, we assessed the subjective and physiological effects of <i>d</i>-amphetamine (AMPH; 10 mg p.o.) after pretreatment with estradiol. Two groups of healthy, regularly cycling women participated in two sessions scheduled during the early follicular phases of two menstrual cycles. One group received estradiol patches (Estraderm TTS; 0.8 mg) which elevated plasma estradiol levels to approximately 750 pg/ml on both sessions; the other group received placebo patches on both sessions. Both groups received AMPH (10.0 mg) and placebo in a randomized and counterbalanced order on the two sessions. Dependent measures included self-report questionnaires, physiological measures, and plasma hormone levels. Most of the subjective and physiological effects of AMPH were not affected by acute estradiol treatment. Nevertheless, estradiol pretreatment increased the magnitude of the effects of AMPH on subjective ratings of ‘pleasant stimulation’ and decreased ratings of ‘want more’. Also, estradiol produced some subjective effects when administered alone: It increased subjective ratings of ‘feel drug’, ‘energy and intellectual efficiency’, and ‘pleasant stimulation’. These results provide limited evidence that the stimulating effects of AMPH are increased by acute estradiol pretreatment.
Potentiated Response of Corticotropin (ACTH) to Repeated Moderate Hemorrhage Requires Amygdalar Neuronal Processing<footref rid="foot01"><sup>1</sup></footref>
Authors: Lilly Michael P. , Putney Dennis J. , Carlson Drew E. 
Published: April 2003

We examined the role of the amygdala in the potentiation of the corticotropin (ACTH) response to a 10 mg/kg hemorrhage by a 1-hour episode of equivalent hypovolemia done 24 h earlier. Unanesthetized rats were studied on the fourth (D1) and fifth (D2) day after chronic implantation of arterial and venous catheters. Immunocytochemistry for Fos protein indicated that neurons in the central and medial nuclei of the caudal amygdala were activated by hemorrhage. We then tested the effect of excitotoxic destruction of the neurons in these areas by bilateral injections of ibotenic acid 10 days prior to catheter placement. In rats that were hemorrhaged on both D1 and D2, the responses of ACTH and corticosterone increased significantly from the first (H1) to the second hemorrhage (H2) in a control group injected with saline (p < 0.05) and in lesioned groups without bilateral damage of the Fos-responsive areas (p < 0.01). In the group with bilateral damage to these sites, the responses to H1 and H2 did not differ. Additional rats had H1 on D2 to control for the long-term effects of the chronic cannulation. The responses of ACTH to H1 on either D1 or D2 did not differ between the saline-injected controls and any of the lesioned groups. In contrast, the response of ACTH to H2 on D2 in rats with bilateral damage of the caudal amygdala was not significant and was less than the response of ACTH to H2 in both rats with unilateral damage of this area (p < 0.05) and those injected with saline (p < 0.05). We conclude that bilateral neuronal processing within the caudal amygdala is required for the potentiation of the response of ACTH to H2 by H1.
Effect of Suckling on Prolactin Receptor Immunoreactivity in the Hypothalamus of the Rat
Authors: Pi Xiujun , Voogt James L. 
Published: April 2003

Previous studies showed that expression of prolactin (PRL) receptor is increased in numerous hypothalamic nuclei in mid-lactating rats. The increase in PRL receptor expression could be initated by neurohormonal changes during proestrus or pregnancy, or by the suckling stimulus during lactation. The present study investigated whether the PRL receptor expression in numerous hypothalamic nuclei is altered by the suckling stimulus. Three groups (n = 4) of rats on lactation day 10 were used: a continuously suckled group, a nonsuckled group (pups removed for 12 h) and a resuckled group (pups removed for 12 and then resuckled for 9 h). Animals were perfused with 2% paraformaldehyde and brains were sectioned (20 µm) for the immunofluorescence study. Immunoreactivity was semiquantitatively analyzed by counting the immunoreactive cells and measuring the immunostaining intensity in a specific area. Neurons expressing PRL receptors were observed in numerous hypothalamic areas with the highest number being in the arcuate, paraventricular and supraoptic nuclei. The PRL receptor immunofluorescence in several nuclei was significantly decreased in the nonsuckled group, and recovered in the resuckled group. These areas included the ventromedial preoptic, ventrolateral preoptic, lateroanterior hypothalamic, ventrolateral hypothalamic and ventromedial hypothalamic nuclei. PRL receptor immunoreactivity in other areas was not significantly altered by the suckling stimulus. These results demonstrate that expression of PRL receptor in hypothalamic nuclei was differentially affected by the suckling stimulus. PRL receptors in those nuclei which were significantly altered by suckling stimulus may play more critical roles during lactation than those areas which were less sensitive to the suckling stimulus.
Induction of Pituitary Adenylate Cyclase-Activating Polypeptide mRNA in the Medial Parvocellular Part of the Paraventricular Nucleus of Rats following Kainic-Acid-Induced Seizure
Authors: Nomura Masayoshi , Ueta Yoichi , Hannibal Jens , Serino Ryota , Yamamoto Yukiyo , Shibuya Izumi , Matsumoto Tetsuro , Yamashita Hiroshi 
Published: April 2003

We examined the effects of kainic acid (KA)-induced seizure on the expression of the pituitary adenylate cyclase-activating polypeptide (PACAP) gene in the paraventricular nucleus (PVN) of rats using in situ hybridization histochemistry. Subcutaneous administration of KA (12 mg/kg) in adult male Sprague-Dawley rats caused a progressive development of seizure behavior. An induction of the PACAP gene expression in the medial parvocellular part of the PVN (mpPVN) was observed 3, 6, 12, 24 and 48 h after subcutaneous administration of KA. From a nearly undetectable level, PACAP gene expression increased in the mpPVN and reached maximum 12 h after subcutaneous administration of KA. PACAP gene expression returned to near basal level 48 h after stimulation with KA. Using a specific monoclonal PACAP antibody, PACAP immunoreactivity (-IR) gradually increased during the following 24 h after KA administration. In controls, PACAP-IR was located exclusively in nerve fibers of the mpPVN, whereas KA administration induced PACAP-IR in cell bodies of the mpPVN, and a dense accumulation of PACAP-IR nerve fibers in the external zone of the median eminence was observed. Induction of the PACAP gene expression following KA-induced seizure was significantly reduced by pretreatment with diazepam or MK-801 (nonselective N-methly-<i>D</i>-aspartate receptor antagonist). These results suggest that PACAP in the hypothalamo-adenohypophysial system may have a hypophysiotropic role during KA-induced seizure.