bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium‐Dependent Effects of Melatonin Inhibition of Glutamatergic Response in Rat Striatum
Authors: Escames G. , Macías M. , León J. , García J. , Khaldy H. , Martín M. , Vives F. , Acuña‐Castroviejo D. 
Published: March 2003

AbstractThe effects of melatonin, amlodipine, diltiazem (l‐type Ca2+ channel blockers) and ω‐conotoxin (N‐type Ca2+ channel blocker) on the glutamate‐dependent excitatory response of striatal neurones to sensory‐motor cortex stimulation was studied in a total of 111 neurones. Iontophoresis of melatonin produced a significant attenuation of the excitatory response in 85.2% of the neurones with a latency period of 2 min. Iontophoresis of either l‐ or N‐type Ca2+ channel blocker also produced a significant attenuation of the excitatory response in more than 50% of the recorded neurones without significant latency. The simultaneous iontophoresis of melatonin + amlodipine or melatonin + diltiazem did not increase the attenuation produced by melatonin alone. However, the attenuation of the excitatory response was significantly higher after ejecting melatonin + ω‐conotoxin than after ejecting melatonin alone. The melatonin–Ca2+ relationship was further supported by iontophoresis of the Ca2+ ionophore A‐23187, which suppressed the inhibitory effect of either melatonin or Ca2+ antagonists. In addition, in synaptosomes prepared from rat striatum, melatonin produced a decrease in the Ca2+ influx measured by Fura‐2AM fluorescence. Binding experiments with [3H]MK‐801 in membrane preparations from rat striatum showed that melatonin did not compete with the MK‐801 binding sites themselves although, in the presence of Mg2+, melatonin increased the affinity of MK‐801. The results suggest that decreased Ca2+ influx is involved in the inhibitory effects of melatonin on the glutamatergic activity of rat striatum.
The Percentage of Pituitary Gonadotropes with Immunoreactive Oestradiol Receptors Increases in the Follicular Phase of the Ovine Oestrous Cycle
Authors: Tobin V. A. , Pompolo S. , Clarke I. J. 
Published: March 2003

AbstractDuring the oestrous cycle, there is an alteration in gonadotrope responsiveness to gonadotropin releasing hormone (GnRH). One cellular mechanism that may be involved in these changes at the pituitary level is the hormonal regulation of oestrogen receptor (ER) expression. Using double‐label immunohistochemistry, we examined the proportion of gonadotropes, lactotropes and somatotropes with immunoreactive (ir) oestrogen receptor alpha (ERα) in pituitary sections from ewes at three stages of the ovine oestrous cycle (n = 8 per group). The percentage of ERα positive cells that also stained positive for luteinizing hormone (LH) increased in the transition from the luteal phase to the follicular phase (n = 8), with no further increase at the time of oestrus (n = 8). In the pituitaries from the luteal phase sheep, only a small number (15%) of lactotropes and 4% of somatotropes were found to contain ir‐ERα and there were no alterations across the oestrous cycle. When we examined pituitaries from ovariectomized (OVX) ewes treated (i.m.) with either oestradiol benzoate (50 µg) or oil vehicle for 2, 4, 6 or 16 h (n = 4 per group), there was no effect of treatment. In fact, the percentage of gonadotropes that were ERα‐positive in OVX ewes was similar to that observed in the pituitaries from the follicular phase ewes, both of which display a high frequency of pulsatile GnRH secretion. We conclude that the number of gonadotropes that contain ir‐ERα increases in the follicular phase of the oestrous cycle and this may enhance the responsiveness of these cells to oestrogen and GnRH. We suggest that this may be due to increased pulsatile GnRH input rather than rising oestrogen levels.
A New Perspective on Glucocorticoid Feedback: Relation to Stress, Carbohydrate Feeding and Feeling Better
Authors: Laugero Kevin D. 
Published: March 2003

AbstractInput to and regulation of activity in the hypothalamic‐pituitary‐adrenal (HPA) axis is diverse and complex. Glucocorticoid feedback is a major component that determines activity in this classic neuroendocrine axis and, while feedback occurs through the brain, the pathways that mediate glucocorticoid feedback remain unknown. In this review, I discuss findings that have led us to view glucocorticoid feedback in the HPA axis in a new light. Much of what has precipitated this view comes from a very surprising finding in our laboratory; sucrose ingestion normalizes feeding, energy balance and central corticotropin releasing factor expression in adrenalectomized (ADX) rats. Since this discovery, a diverse set of literature that supports this view of glucocorticoid feedback has been found. Taken together, recent findings of the well‐known importance of glucocorticoids to feeding and energy balance, and the modulatory actions of carbohydrate ingestion on both basal and stress‐induced activity in the HPA axis, strongly suggest that many metabolic (e.g. obesity) and psychological (e.g. depression) pathologies, which often present together and have been associated with stress and HPA dysregulation, might, in part, be understood in light of our new view of glucocorticoid feedback.
Increased Galanin Synapses onto Activated Gonadotropin‐Releasing Hormone Neuronal Cell Bodies in Normal Female Mice and in Functional Preoptic Area Grafts in Hypogonadal Mice
Authors: Rajendren G. 
Published: March 2003

AbstractGalanin synaptic input onto gonadotropin‐releasing hormone (GnRH) neuronal cell bodies was analysed in female mice using the presynaptic vesicle‐specific protein, synaptophysin (Syn) as a marker. In the first experiment, forebrain sections from normal ovariectomized ovarian steroid‐primed mice exhibiting a surge of luteinizing hormone were processed for immunohistochemical labelling for GnRH, synaptophysin, galanin and Fos. Two representative sections from each brain, one passing through the anterior septum (anterior section) and the other through the organum vasculosum lamina terminalis‐preoptic area (posterior section), were analysed under the confocal microscope. None of the GnRH cells analysed in the anterior sections were Fos immunoreactive (IR) or received input from galanin‐IR fibres. In contrast, the majority of GnRH cells in the posterior sections analysed were Fos‐positive. The number of galanin synapses onto the Fos‐positive GnRH cells was significantly higher than that in the Fos‐negative cells in this area of the brain, even though the number of Syn‐IR appositions was comparable to each other. Transplantation of preoptic area (POA) into the third cerebral ventricle of hypogonadal (HPG) mice corrects deficits in the reproductive system. In the second experiment, synaptic input to GnRH cells was compared between HPG/POA mice with (functional graft) or without (nonfunctional graft) gonadal development. The mean numbers of Syn‐IR appositions and galanin synapses per GnRH cell and the proportion of GnRH cells with galanin input were significantly higher in the functional than in the nonfunctional grafts. The results suggest that galanin can act directly on the GnRH cell bodies and may have an important regulatory role on the GnRH system.
Chronic Neuropeptide Y Y5 Receptor Stimulation Suppresses Reproduction in Virgin Female and Lactating Rats
Authors: Toufexis D. J. , Kyriazis D. , Woodside B. 
Published: March 2003

AbstractContinuous infusion of neuropeptide Y (NPY) disrupts cyclicity and delays the onset of puberty in female rats indicating that NPY can suppress reproduction. Central application of NPY also reliably increases food intake in rats. States with heavy demands on energy resources where reproduction is also inhibited, such as lactation, are similarly accompanied by elevations in central NPY expression. In previous studies, we have shown that, compared to lactating rats fed ad libitum, food‐restricted lactating rats exhibit a longer period of lactational diestrus that is correlated with increased central NPY expression. These studies link NPY to the inhibition of reproduction that is mediated by low availability of energy resources. Here, we examine the effect of chronic 7‐day infusion of the mixed Y1/Y4/Y5 agonist (Leu31, Pro34) NPY and selective agonists to the Y2 (NPY13‐36) and Y5 (D‐Trp32 NPY and D‐Trp34 NPY) receptors on food intake and the oestrous cycle of virgin female rats. We also investigated the effect of chronic infusion from day 8–15 postpartum (pp) of D‐Trp32 NPY and D‐Trp34 NPY on food‐intake and the length of lactational diestrus in lactating rats fed ad libitum. In virgin females, infusion of (Leu31, Pro34) NPY and both the Y5 agonists lengthened the period between consecutive oestrus days while the Y2 agonist NPY13–36 was without effect. Selective Y5 receptor activation alone caused an increase in food intake in virgin females. In lactating females, D‐Trp32 NPY extended the length of lactational diestrus, while D‐Trp34 NPY had no effect on this parameter. These data suggest that Y5 receptor activation suppresses the reproductive axis in both virgin and lactating rats and that Y5 receptor activation enhances food‐intake in virgin females.
Prostaglandin F2α‐Induced Nest‐Building Behaviour is Associated with Increased Hypothalamic c‐fos and c‐jun mRNA Expression
Authors: Walton S. L. , Burne T. H. J. , Gilbert C. L. 
Published: March 2003

AbstractIntramuscular injection of the naturally occurring prostaglandin F2α (PGF2α) to sexually mature female pigs induces luteolysis and rapidly elicits a behavioural response consistent with pre‐partum nest‐building. Intramuscular injection of the synthetic prostaglandin F2α (cloprostenol) also induces luteolysis but no nest‐building behaviour is observed. The effects of PGF2α, but not cloprostenol, on nest‐building behaviour may be mediated via peripheral PGF2α receptors (FP) or via direct action on central FP receptors. We have previously shown FP receptor mRNA to be localized in porcine paraventricular nucleus (PVN), supraoptic nucleus (SON) and pars dorso‐medialis of the suproptic nucleus (SOD), suprachiasmatic nucleus, choroid plexus and anterior and intermediate pituitary lobes. In this experiment, we examined hypothalamic expression of the immediate early genes c‐fos and c‐jun mRNA after treatment with PGF2α or cloprostenol. Twenty‐one 8‐month‐old nulliparous female pigs (gilts) were injected intramuscularly with a luteolytic dose of PGF2α (15 mg), cloprostenol (175 µg) or saline control, their behaviour was recorded and they were killed 60 min later. Coronal hypothalamic sections and control ovarian tissues were incubated with 45‐mer oligonucleotide probes complementary to porcine c‐fos and c‐jun genes using standard in situ hybridization histochemistry techniques. Significantly higher c‐fos and c‐jun mRNA expression was found in PGF2α‐treated compared to saline or cloprostenol‐treated pigs in the PVN, SON and SOD. Significantly higher c‐fos and c‐jun mRNA expression was found in corpus lutea of PGF2αand cloprostenol‐treated pigs compared to saline controls. Treatment with PGF2α induced nest‐building behaviour whereas treatment with cloprostenol and saline did not. This suggests that PGF2α, or one of its metabolites, and not cloprostenol, crosses the blood–brain barrier and acts directly on hypothalamic receptors to mediate its effect on nest‐building behaviour.
Lipopolysaccharide‐Induced Oestrogen Receptor Regulation in the Paraventricular Hypothalamic Nucleus of Lewis and Fischer Rats
Authors: Tonelli L. , Kramer P. , Webster J. I. , Wray S. , Listwak S. , Sternberg E. 
Published: March 2003

AbstractOestrogen receptor (ER) regulation of gene transcription in neurosecretory and pituitary cells has been proposed as an important mechanism for increased hypothalamic‐pituitary‐adrenal (HPA) axis responses in females of several mammalian species, including humans. Inbred female Fischer (F344/N) and Lewis (LEW/N) rats have similar oestrogen levels, although Fischer rats exhibit hyper‐ and Lewis rats hypo‐HPA axis responses. The blunted HPA axis response of Lewis rats has been associated with their blunted hypothalamic corticotropin releasing hormone (CRH) expression. To determine if the female CRH expression deficiency in Lewis rats is associated with defective ER expression and regulation, hypothalamic paraventricular nucleus (PVN) transcript levels of CRH and ER were determined under basal conditions and after immune challenge. Microdissected PVN were obtained from control and lipopolysaccharide (LPS) treated Lewis and Fischer rats and CRH, ERα and β mRNA levels were determined by semiquantitative reverse‐transcriptase‐polymerase chain reaction. In addition, ERα and β protein levels were determined by semiquantitative Western blots. ERα and β mRNA and protein levels in the PVN of control Fischer rats were significantly higher than in control Lewis rats. ERα and β mRNA and protein levels in Fischer rats were reduced by LPS administration at the time of maximal CRH mRNA levels but did not change in Lewis rats, an effect independent of oestrogen levels. These data indicate that defective neuroendocrine HPA axis responses are associated with defective ER expression and regulation in Lewis PVN despite oestrogen concentrations.
Syrian Hamster and Rat Display Developmental Differences in the Regulation of Pineal Arylalkylamine N‐Acetyltransferase
Authors: Garidou M.‐L. , Ribelayga C. , Pevet P. , Simonneaux V. 
Published: March 2003

AbstractIn the Syrian hamster, the role of noradrenaline in the regulation of melatonin synthesis is less clear than in the rat. During pineal ontogenesis in the rat, noradrenaline is the major transmitter involved in the onset of melatonin synthesis and melatonin rhythm. We analysed the involvement of noradrenaline in the ontogenesis of melatonin synthesis in the Syrian hamster and compared it with that of the rat. We followed the developmental profile of melatonin content in parallel with those of mRNA expression and activity of AA‐NAT, the melatonin rhythm‐generating enzyme. In addition, we tested the effect of noradrenergic drugs at early steps of pineal ontogenesis. In the Syrian hamster, the night‐time Aa‐nat mRNA, first detected 3 days after birth, increases progressively up to a maximum reached at 30 days of age and then decreases significantly towards adulthood. The daytime level of Aa‐nat mRNA remains always low. A significant day/night rhythm appears 10 days after birth, is maximal (200‐fold nocturnal increase) 30 days after birth and decreases slowly towards adulthood. Ontogenesis of the AA‐NAT activity rhythm is similar, although with a much lower amplitude of day/night variations (four‐fold). The developmental pattern of melatonin content is similar to that of AA‐NAT and could be correlated with the appearance of sympathetic innervation in the pineal gland. However, neither α‐ nor β‐adrenergic antagonists inhibit the night‐time Aa‐nat mRNA transcription in the 9‐day‐old Syrian hamster, in contrast to what is observed in the adult. For comparison, the β‐adrenergic antagonist propranolol inhibits Aa‐nat gene expression in 2‐day‐old rat. These results show that both species are different in the regulation of the appearance of melatonin synthesis and that Syrian hamster is peculiar from birth in term of noradrenaline involvement in the activation of melatonin synthesis.
Isolation and Structure–Bioactivity Characterization of Glycosylated N‐Pro‐Opiomelanocortin Isoforms
Authors: Lu J. , Swinnen E. , Proost P. , De Vreese B. , Vankelecom H. , Denef C. 
Published: March 2003

AbstractThe N‐terminal fragment of mouse pro‐opiomelanocortin (N‐POMC) was isolated from AtT‐20 cell‐conditioned medium on the basis of immunoreactivity to an anti‐POMC1‐50 monoclonal antibody by a concentration step, a cation exchange step, reversed phase high‐performance liquid chromatography (HPLC) and size exclusion HPLC. Two groups of N‐POMC isoforms with a molecular weight (MW) of approximately 11 kDa and 13 kDa, respectively, were identified by mass spectrometry and N‐terminal amino acid sequencing. C‐terminal sequencing indicated that 11 kDa isoforms correspond to POMC1‐74 and 13 kDa isoforms to POMC1‐95. Isoforms from both groups enhanced the prolactin mRNA content (measured by means of TaqMan real‐time reverse transcription‐polymerase chain reaction) in cultured rat pituitary cell aggregates in a dose‐dependent manner, but not all of them showed this activity. POMC1‐74 compounds were significantly more potent than POMC1‐95 isoforms. The observed effects were abolished by coincubation with the monoclonal anti‐POMC1‐50 antibody, showing the specificity of this biological action. Incorporation of bromodeoxyuridine into DNA of immunostained lactotrophs was enhanced by only a minor part of the isoforms. Some of these had no effect on prolactin mRNA expression. The N‐POMC isoforms appeared to be N‐ and at least in part O‐glycosylated. After enzymatic N‐deglycosylation of selected N‐POMC isoforms, the stimulatory effect on the prolactin mRNA level was depressed (in case of the POMC1‐95 isoforms) or totally abolished (in case of the POMC1‐74 isoforms). The present findings show that N‐POMC is a mixture of differentially glycosylated isoforms, that the isoforms of POMC1‐74 are the biologically more effective forms and that different isoforms induce different biological responses in the same cell population. The data also show the essential role of N‐glycosylation in the biological response.
Orexin‐A Immunoreactivity and Prepro‐Orexin mRNA Expression in Hyperphagic Rats Induced By Hypothalamic Lesions and Lactation
Authors: Sun G. , Narita K. , Murata T. , Honda K. , Higuchi T. 
Published: March 2003

AbstractOrexins are endogenous neuropeptides that potently facilitate appetite and food consumption. In the present study, we examined orexin immunoreactivity and prepro‐orexin mRNA expression in the lateral hypothalamus by immunohistochemistry and competitive reverse transcription‐polymerase chain reaction (RT‐PCR) methods in different models of hyperphagia in rats. Hyperphagia was induced by lesions of either the ventromedial hypothalamus (VMHL) or the paraventricular nucleus (PVNL), and we also compared lactating rats to nonlactating controls. Both VMHL and PVNL increased food intake and body weight compared to shams. On day 7 post lesion, serum leptin and insulin concentrations exhibited 3.2‐ and 2.8‐fold increases in VMHL rats, and nonsignificant 1.8‐ and 1.8‐fold increases in PVNL rats; there were significant decreases (48% and 33%) in lactating rats on day 12 postpartum compared to controls, respectively. Serum glucose concentrations were not significantly changed compared to controls in these rats. Quantification by image analysis suggests that VMHL significantly decreased the number and mean staining intensity of orexin‐A immunoreactive neurones compared to those in the sham‐lesioned group; while PVNL did not change orexin‐A immunoreactivity. Competitive RT‐PCR analysis showed that VMHL significantly decreased the prepro‐orexin mRNA expression compared to those in the sham‐lesioned group, and PVNL did not change it. Lactating rats on days 11–12 of lactation had significantly greater number and mean staining intensity of orexin‐A immunoreactive neurones, prepro‐orexin mRNA expression food intake and body weight than nonlactating postpartum rats. Thus, changes in orexin‐A immunoreactivity and prepro‐orexin mRNA expression were not consistent between the hyperphagia models. These results suggest that the hyperphagia from VMHL or PVNL and lactating rats differ in their involvement of orexin‐A, and the change in circulating leptin and insulin concentrations may be involved in the change of orexin‐A immunoreactivity in these rats.
Serotonin Receptors Involved in Vasopressin and Oxytocin Secretion
Authors: Jørgensen H. , Riis M. , Knigge U. , Kjær A. , Warberg J. 
Published: March 2003

AbstractSerotonin (5‐HT), 5‐HT agonists, the 5‐HT precursor 5‐hydroxytryptophan, 5‐HT‐releasers and ‐reuptake inhibitors stimulate the release of vasopressin and oxytocin. We investigated the involvement of 5‐HT receptors in the serotonergic regulation of vasopressin and oxytocin secretion. Vasopressin and oxytocin secretion was stimulated by 5‐HT, the 5‐HT1A+1B+5A+7 agonist 5‐carboxamidotryptamine (5‐CT), the 5‐HT2A+2C agonist DOI, the 5‐HT2C+2A agonist mCPP, the 5‐HT2C agonist MK‐212, the 5‐HT3 agonist SR 57277 and the 5‐HT4 agonist RS 67506. The 5‐HT1A agonist 8‐OH‐DPAT, which had no effect on vasopressin secretion, stimulated oxytocin secretion. The 5‐HT‐induced release of vasopressin and oxytocin was inhibited by central infusion of the 5‐HT antagonists WAY 100635 (5‐HT1A), LY 53857 (5‐HT2A+2C), ICS 205‐930 (5‐HT3+4) and RS 23597 (5‐HT4). The 5‐HT2+6+7 antagonist metergoline in combination with the 5‐HT1A+2+7 antagonist methysergide inhibited the stimulatory effect of 5‐CT on both hormones, whereas the 5‐HT1A+1B antagonist cyanopindolol only inhibited the oxytocin response. The 5‐HT2A antagonist 4‐(4‐flourobenzoyl)‐1‐(4‐phenylbutyl)‐piperidine oxalate had no effect on DOI‐induced hormone response. The 5‐HT2C antagonist Y 25130 partly inhibited the stimulating effect of MK‐212. ICS 205‐930 and RS 23597 inhibited vasopressin and oxytocin secretion induced by RS 67506. WAY 100635 inhibited 8‐OH‐DPAT‐induced oxytocin secretion. We conclude that 5‐HT‐induced vasopressin secretion primarily is mediated via 5‐HT2C, 5‐HT4 and 5‐HT7 receptors, whereas 5‐HT2A, 5‐HT3 and 5‐HT5A receptors seem to be of minor importance. 5‐HT‐induced oxytocin secretion involves 5‐HT1A, 5‐HT2C and 5‐HT4 receptors; in addition an involvement of 5‐HT1B, 5‐HT5A and 5‐HT7 receptors seems likely, whereas 5‐HT2A and 5‐HT3 receptors seem to be less important.
In Vitro Effects of Catecholamines and Catecholestrogens on Brain Tyrosine Hydroxylase Activity and Kinetics in the Female Catfish Heteropneustes fossilis
Authors: Chaube R. , Joy K. P. 
Published: March 2003

AbstractEffects of catecholamines and catecholestrogens on tyrosine hydroxylase (TH) activity and kinetics were investigated in the telencephalon and hypothalamus of female Heteropneustes fossilis in gonad quiescent (resting) and recrudescent (preparatory) phases. Dopamine, noradrenaline and adrenaline and the catecholestrogen, 2‐hydroxyestradiol‐17β inhibited TH activity in a concentration‐dependent manner in both resting and preparatory phases, with a higher effect in the resting phase. Two‐ methoxyestradiol‐17β did not alter TH activity in any season. The catecholamines inhibited TH in a competitive manner increasing apparent Km values significantly without altering the apparent Vmax. Two‐hydroxyestradiol‐17β inhibited significantly the enzyme in a noncompetitive manner and decreased apparent Vmax without altering apparent Km values. The apparent Ki is higher for dopamine than noradrenaline or adrenaline. The apparent Ki for 2‐hydroxyestradiol‐17β is not significantly different from that of noradrenaline. The present results suggest an interaction between oestradiol‐17β (E2) and catecholamine metabolism at the level of tyrosine hydroxylation and E2 effects on catecholamines may be mediated through its 2‐hydroxylation.