bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increased Fos Expression in Oxytocin Neurons Following Masculine Sexual Behavior
Authors: Witt Diane M. , Insel Thomas R. 
Published: September 2006

AbstractInduction of the c‐fos protein product (Fos) was used to immunocytochemically identify oxytocin (OT) neurons that may be activated during copulatory interactions. Fos induction was quantified in sexually‐experienced male rats after either (a) exposure to a testing arena recently vacated by an estrous female, (b) copulatory interactions such as mounting and intromission without ejaculation, or (c) mounting and intromissions culminating in ejaculation. In the parvocellular regions of the paraventricular nucleus of the hypothalamus (PVN), the number of neurons expressing Fos increased following either intromission (53%) or ejaculation (124%). Significant, but less striking, increases in the number of cells expressing Fos were noted in magnocellular regions of the PVN where intromission resulted in a 13% increase and ejaculation in a 49% increase in Fos. The number of perikarya immunoreactive for OT and AVP did not differ as a function of increasing sexual contacts. In control (novel arena) males, 33–73% of the Fos labeling occurred in OT cells. Sexual interactions did not enhance the number of double‐labeled cells in most parvocellular regions. However, in lateral parvocellular regions located in the most caudal aspects of the PVN, 31% of the Fos‐positive cells occurred in OT neurons in ejaculated males, while in control males none of the OT cells were double‐labeled. This PVN subdivision is known to consist of neurons that project to the brain stem and spinal cord at lumbar levels which contain motor neurons that regulate penile reflexes. The present data suggest a possible neurochemical circuit which incorporates oxytocinergic neurons in the mediation of masculine sexual responses.
Characterization and Localization of Mouse Hypothalamic Growth Hormone‐Releasing Factor and Effect of Gold Thioglucose‐Induced Hypothalamic Lesions
Authors: Miki Nobuhiro , Ono Masami , Asakawa‐Yasumoto Kumiko , Aoki Tomoko , Murata Yoji , Ishituka Yuichi , Demura Hirosi , Sasaki Fumihiko 
Published: September 2006

AbstractHypothalamic growth hormone‐releasing factor (GRF) in higher mammals, including human GRF, is a 44 amino acid residue peptide and is highly homologous in structure. By contrast, mouse GRF (mGRF) recently deduced by cDNA cloning consists of only 42 residues and shows relatively low homology to the GRFs of higher mammals and the same rodent species, rat. To characterize and localize the predicted mature mGRF peptide in the hypothalamus, we have generated its antiserum and developed a homologous radioimmunoassay. Immunoreactive mGRF in the acid hypothalamic extract was eluted as a single peak at a position identical to that of synthetic peptide on both gel filtration chromatography and reverse‐phase high‐performance liquid chromatography (HPLC). Secretion of immunoreactive mGRF from incubated hypothalami increased several fold in response to 50 mM K+, and this rise was abolished in the absence of medium Ca2+. Only a single peak of immunoreactive mGRF that coeluted with synthetic replicate was observed after the K+ ‐stimulated medium was extracted on Bond Elut C18 cartridges and applied on reverse‐phase HPLC. Immunohistochemistry identified many mGRF‐positive cell bodies in the arcuate nucleus and dense bundles of immunoreactive fibers in the median eminence. Treatment of mice with gold thioglucose (GTG), a chemical agent known to cause hypothalamic lesions, markedly depleted both content and in vitro secretion of immunoreactive mGRF. The decline in mGRF secretion was greater in GTG obese than in nonobese mice, whereas somatostatin secretion was not affected by GTG treatment. As compared to the previous findings obtained on rat GRF, mouse had approximately the same content of hypothalamic GRF, but retained only one third the capacity to release GRF in response to the same depolarizing stimulus.These findings demonstrate that mouse hypothalamus contains and secretes a mGRF‐like molecule which has immunological and chromatographic characteristics identical to that predicted by molecular cloning. The depolarization‐evoked, Ca2+‐dependent release of immunoreactive mGRF and its neuronal localization in the arcuate nucleus‐median eminence region indicate that it functions as a hypophysiotropic hormone of physiological importance. GTG produces hypothalamic GRF deficiency, probably sparing hypophysiotropic somatostatin neurons, and could be used to generate a mouse model for human GRF‐deficient dwarfism.
Stress and Interleukin‐1 β‐Induced Activation of c‐fos, NGFI‐B ann CRF Gene Expression in the Hypothalamic PVN: Comparison Between Sprague‐Dawley, Fisher‐344 and Lewis Rats
Authors: Rivest Serge , Rivier Catherine 
Published: September 2006

AbstractVarious signals are known to activate the hypothalamic‐pituitary‐adrenal (HPA) axis, an event largely dependent on the release of corticotropin‐releasing factor (CRF) which originates mainly from the parvocellular paraventricular nucleus (PVN) of the hypothalamus. These signals include neurogenic stimuli such as exposure to mild electroshocks, and systemic stimuli like administration of cytokines. The HPA axis activity of Lewis rats has been reported to be hyporesponsive to such stimuli, but the exact mechanisms involved in this phenomenon are poorly understood. The present study investigated the effect of footshock exposure and central injection of interleukin (IL)‐1β, on CRF neuronal activity and gene expression in the PVN of adult male Sprague‐Dawley (SD), Fisher‐344 (F344) and Lewis (LEW) rats. The animals were deeply anesthetized and rapidly perfused transcardially with a solution of 4% paraformaldehyde 3 h after the beginning of the footshock session (1.5 mA, 2 s duration, 4/min over 1 h), or the i.c.v. injection of IL‐1β (100 ng in 10 μl). mRNA encoding the immediate ‘early’ genes (lEGs) c‐fos and NGFI‐B, as well as CRF, were assayed by in situ hybridization histochemistry, while the localization of Fos protein within CRF‐immunoreactive (ir) neurons in the PVN was determined using a dual immunostaining protocol. Both stress and IL‐1β induced robust Fos‐ir expression within the parvocellular division of the PVN in all 3 strains. The number of cells immunoreactive for both Fos and CRF proteins in the PVN was similar in SD, F344 and LEW rats following either challenge. While control animals did not display detectable levels of c‐fos or NGFI‐B mRNA in the PVN, both treatments induced significant expression of these transcripts in this hypothalamic nucleus and no significant differences were observed among SD, F344 and LEW rats. Relative levels of CRF mRNA in the PVN were also significantly and comparably increased following either stress or central IL‐1β treatment. In contrast, plasma ACTH and corticosterone levels were significantly higher in F344 and SD rats than in LEW animals during the stress session.These results provide further evidence that physical stress and central IL‐1β can enhance expression of several lEGs, as well as CRF, within the parvocellular division of the PVN. These independent indices of functional activation within parvocellular CRF neurons appear to respond similarly to diverse challenges in adult male SD, F344 and LEW rats. Thus, these findings suggest that the hyporesponsiveness of LEW HPA axis to stress does not seem to be a consequence of a defect in afferent signals to the parvocellular PVN, at least in mature male rats.
Neuropeptide‐Y Stimulates Pituitary‐Adrenal Activity in Fetal and Adult Sheep
Authors: Brooks A. N. , Howe D. C. , Porter D. W. F. , Naylor A. M. 
Published: September 2006

AbstractCorticotrophin‐releasing factor (CRF) and arginine vasopressin (AVP) are the primary neuropeptides regulating the secretion of ACTH from the anterior pituitary gland during fetal and adult life. However, a number of other neuropeptides including neuropeptide‐Y (NPY) appear to modulate the activity of this system. The potential role of NPY in the regulation of pituitary‐adrenal function was examined in fetal and adult sheep. Administration of NPY (6.5 μg) as a bolus injection into the third cerebral ventricle of adult ewes elicited a significant (P<0.05) increase in plasma concentrations of ACTH. In fetal sheep at day 125 gestation (term = 145 days) a five‐fold higher dose (30 μg) of NPY injected into the lateral cerebral ventricles also caused a significant increase in plasma concentrations of ACTH. The potential of NPY to influence ACTH secretion directly from the pituitary gland was investigated using primary cultures of fetal (day 130 gestation) and adult pituitary cells. CRF (10−10–10−7 M) caused a significant (P<0.01) dose‐related increase in ACTH secretion from both fetal and adult pituitary cells. Furthermore, the secretion of ACTH from adult cells was significantly greater (P<0.05) than that from fetal cells. NPY (10−10–10−7 M) had no effect on basal or CRF‐stimulated ACTH secretion from fetal or adult pituitary cells. Pre‐incubation of pituitary cells with cortisol (10−9 and 10−7 M) for three days significantly inhibited CRF‐stimulated ACTH secretion but had no effect on basal ACTH release. The simultaneous addition of NPY did not alter the ability of cortisol to inhibit CRF‐stimulated ACTH secretion.These data show that exogenous administraiton of NPY stimulates pituitary‐adrenal activity in fetal and adult sheep. The lack of any direct pituitary effects of NPY suggests that this neuropeptide acts centrally within the brain to exert its effects on the pituitary‐adrenal axis.
Characterization of Membrane‐Associated Peptidase Activities Expressed by Endothelial Cells of the Ovine Median Eminence
Authors: Lew Rebecca A. , Tetaz Tim , Smith A. Ian 
Published: September 2006

AbstractThe capillary endothelial cells of the median eminence represent a potential site for the degradation/modification of both circulating and hypothalamic peptides passing through the hypophysial portal system toward the pituitary. This study examines endothelial cell peptidase expression in vitro by monitoring the metabolism of gonadotropin‐releasing hormone (GnRH) by cultured endothelial cells from sheep median eminence. Cleavage of GnRH by median eminence endothelial cell membranes generated GnRH1–5 as the primary stable product, which was then degraded to GnRH1–3 and free amino acids. Degradation of GnRH was completely inhibited by TPCK, ZnCI2 and N‐ethylmaleimide, and partially inhibited by EDTA and by a specific inhibitor of the metalloendopeptidase EC 3.4.24.15, CFP‐AAY‐pAB. Interestingly, an increase in GnRH1–9 production was seen with the latter inhibitors, suggesting a two‐step mechanism of GnRH degradation involving a primary cleavage at the Pro9‐Gly10‐NH2 bond, inhibitable by TPCK, ZnCI2, and NEM, followed by cleavage by EC 3.4.24.15 to generate GnRH1–5. Phosphoramidon and angiotensin converting enzyme inhibitors (as well as other non‐specific inhibitors) were without effect, indicating that endopeptidase EC 3.4.24.11 and angiotensin converting enzyme are not involved. Neither bovine aortic endothelial cell nor AtT‐20 cell membranes exhibited this pattern of peptidase activity. Degradation of GnRH by intact median eminence endothelial cells in culture was also observed, suggesting an extracellular orientation for these enzymes; the potential role of such peptidases in the fine regulation of both pituitary function and local blood flow is currently under investigation.
Opioids and Coupling of the Anterior Peri‐Third Ventricular Input to Oxytocin Neurones in Anaesthetized Pregnant Rats
Authors: Bull Philip M. , Douglas Alison J. , Russell John A. 
Published: September 2006

AbstractIn the pregnant rat the osmotic drive to oxytocin neurones is reduced and oxytocin secretion itself is inhibited by endogenous opioids. Coupling of the anterior peri‐third ventricular input pathway, involved in osmoregulation, to magnocellular oxytocin neurones was studied in urethane‐anaesthetized virgin and 21 day pregnant rats using electrical stimulation of the region anterior and ventral to the third cerebral ventricle (AV3V region) to drive the oxytocin neurones, and giving naloxone to prevent the action of any endogenous opioids on the system. Trains ofstimuli (0.5 mA, 1 ms pulses, 10 s on 10 s off, at either 10 Hz or 25 Hz for 10 or 2 min respectively) were given at 20 or 30 min intervals via an electrode stereotaxically‐implanted in the AV3V region, and femoral arterial blood plasma samples collected immediately before and after each stimulation were radioimmunoassayed for oxytocin concentration. The first (control) AV3V stimulation increased plasma oxytocin concentration reproducibly and similarly in virgin and 21‐day pregnant rats. Naloxone administered 10 min before the second stimulus increased basal plasma oxytocin concentration in virgin and pregnant rats and increased the oxytocin secretory response to 25 Hz AV3V stimulation in virgin but not pregnant rats, and the response was significantly greater in virgin rats. Naloxone reveals oxytocin secretion unrestrained by endogenous opioids, therefore it appears that there is an opioid‐independent reduction in the excitatory coupling of the AV3V input to oxytocin neurones which may explain the reduced osmoresponsiveness of oxytocin neurones at the end of pregnancy. In other experiments, morphine (μ‐opioid agonist; at 1 & 5 mg/kg 5 min before the second and third stimulation periods respectively) or U50,488 (κ‐opioid agonist; 0.5 and 2.5 mg/kg respectively) was given to test the opioid sensitivity of the oxytocin neurone response to stimulation of the AV3V input. Morphine did not significantly affect the oxytocin secretory response to 25 Hz AV3V stimulation in either virgin or pregnant rats but there was a significant dose related inhibition of the oxytocin secretory response to 10 Hz stimulation in both groups. U50,488 also inhibited the oxytocin secretory response to 25 Hz AV3V stimulation in a dose‐related manner in both virgin and pregnant rats. The inhibitory effects of morphine and U50,488 were not different between virgin and pregnant rats; this indicates that central opioid interactions with the AV3V input to oxytocin neurones are not changed in pregnancy. The initial similar oxytocin secretory response to AV3V stimulation in pregnant and virgin rats seems to be a product of a reduced effectiveness of the excitatory AV3V input to oxytocin neurones in late pregnancy and the previously established reduced posterior pituitary sensitivity to inhibitory endogenous opioids.
Steroidal and Photoperiodic Regulation of Opiate Binding in Male Golden Hamsters
Authors: Tubbiola Maureen L. , Bittman Eric L. 
Published: September 2006

AbstractThis study was designed to investigate interactions between daylength and testosterone (T) in the regulation of 3H‐naloxone binding which may contribute to seasonal changes in the negative feedback and behavioral effects of androgens in the golden hamster. Photoperiod influenced opiate binding in hamsters with intact gonads only in the medial amygdala. Castration elevated specific 3H‐naloxone binding in the medial amygdala, medial preoptic nucleus, bed nucleus of the stria terminalis, and in the basolateral amygdaloid nucleus of hamsters exposed to either long (14L:10D) or short (5L:19D) days. Exposure to SD renders hamsters less sensitive to T maintenance in reversing these effects. Delay of T replacement until 5 weeks after castration eliminated the ability of this androgen to reverse the influence of castration upon opiate receptors in the medial amygdala. Pinealectomy markedly increased 3H‐naloxone binding in short days in several brain areas.The data demonstrate that androgens and photoperiod interact to regulate 3H‐naloxone binding, particularly in the medial amygdala. These effects may play a functionally relevant role in seasonal changes in the expression of sexual behavior and/or gonadotropin secretion.
Patch‐Clamp Analysis of Direct Steroidal Modulation of Glutamate Receptor‐Channels
Authors: Wong Michael , Moss Robert L. 
Published: September 2006

AbstractSteroid hormones regulate the neuroendocrine and behavioral functions of the brain by using a number of diverse cellular mechanisms. Many steroids exert rapid electrophysiological effects on neurons, involving specific interactions with membrane components, such as neurotransmitter receptors. Previous studies suggest that the steroids, estrogen and pregnenolone sulfate (PS), might directly modulate glutamate receptors. The present experiments utilized patch‐clamp recording of glutamate receptor‐channels in excised membrane patches to test for direct modulation by these steroids. Characteristic single‐channel activity from N‐methyl‐D‐aspartate (NMDA) receptors could be elicited in both inside‐out and outside‐out patches excised from acutely dissociated hippocampal neurons. PS, but not 17ß‐estradiol, increased the open probability of NMDA channel activity in inside‐out and outside‐out patches. The PS‐induced increase in open probability could be attributed to an increase in both frequency of opening and mean open time of the NMDA receptor, though the effect on frequency of opening was more prominent. The non‐NMDA agonist, kainate, induced continuous shifts and increased noise in the baseline current of outside‐out patches, but rarely activated clearly resolvable single‐channel openings. 17ß‐estradiol and PS had no apparent effect on the kainate‐induced currents. These findings suggest that some steroids can directly modulate glutamate receptors, but other steroids may utilize indirect mechanisms for regulating glutamatergic synaptic transmission.
Electrical Stimulation of the Rat Periventricular Nucleus Influences the Activity of Hypothalamic Arcuate Neurones
Authors: Dickson Suzanne L , Leng Gareth , Robinson Iain C.A.F. 
Published: September 2006

AbstractIn rats, the release of growth hormone (GH) is inhibited during electrical stimulation of the periventricular nucleus but after the end of stimulation, there is a rebound ‘hypersecretion’ of GH. We examined the responses of arcuate neurones in pentobarbitone‐anaesthetized male rats, following electrical stimulation of the periventricular nucleus to test the hypothesis that the effects of periventricular nucleus stimulation on GH secretion are mediated via effects upon GH‐releasing hormone (GRF) neurones in the arcuate nucleus. The electrical activity of 2 groups of arcuate neurones were analysed before, during and after periventricular nucleus stimulation (10 Hz, 5 min, 0.5 mA biphasic, 0.5/1.0 ms): a) putative neurosecretory cells which were antidromically identified (AD) as projecting to the median eminence (n = 53) and b) non‐neurosecretory cells, identified by their spontaneous ‘bursting’ pattern of activity (n = 29). During stimulation predominantly inhibitory responses were observed in both AD and bursting cell groups. Of the 39 AD cells which were spontaneously active, 25 were inhibited during the periventricular nucleus stimulation, and 10 of these showed a rebound hyperactivation following the end of stimulation. Fifteen bursting cells were inhibited during stimulation and 4 of these displayed a rebound hyperactivation following the end of stimulation. Additional evidence was sought for the identity of these cells by testing their response to electrical stimulation of the basolateral amygdala (which has previously been shown to increase plasma GH concentration without influencing the release of other pituitary hormones). Six of the 10 AD cells which displayed the inhibition/rebound response to periventricular nucleus stimulation were also excited following electrical stimulation of the basolateral amygdala. We conclude that 1) electrical stimulation of the periventricular nucleus and the basolateral amygdala exert predominantly inhibitory and excitatory effects respectively upon the activity of arcuate neurones but for neither site were the effects of stimulation exclusively upon GRF neurones, and 2) the rebound hypersecretion of GH following PeN stimulation is likely to involve the rebound activation of arcuate neurones.
Systemic Osmotic Stimulation Increases Vasopressin and Oxytocin Release Within the Supraoptic Nucleus
Authors: Ludwig Mike , Callahan Michael F. , Neumann Inga , Landgraf Rainer , Morris Mariana 
Published: September 2006

AbstractVasopressin (VP) and oxytocin (OT) are released within the hypothalamic nuclear region in response to direct microdialysis with hypertonic solutions. Experiments were performed to determine whether systemic osmotic stimulation causes changes in intranuclear peptide release within the supraoptic nucleus (SON). A hypertonic sodium chloride solution was injected intraperitoneally (ip) or intravenously (iv) and microdialysis techniques were used to simultaneously monitor central and peripheral peptide release in urethane anesthetized rats. Systemic osmotic stimuli elicited increases in intranuclear peptide release which were delayed and long‐lasting, occurring over a 2.5 h period. In contrast, plasma peptide levels peaked at 30‐min after the stimulus. The results demonstrate that increased plasma sodium elicits an increase in VP and OT release into the extracellular space of the hypothalamic SON. The different patterns of peptide release in plasma and brain point toward the possibility of independently regulated release into the different compartments.
Hypothalamic‐Pituitary‐Adrenal Activation Following Endotoxin Administration in the Developing Rat: A CRH‐Mediated Effect
Authors: Shanks Nola , Meaney Michael J. 
Published: September 2006

AbstractThe present studies assessed hypothalamic‐pituitary‐adrenal (HPA) responses following immune activation with endotoxin (ip) in three‐day old Long Evans rats. Marked plasma corticosterone (B), adrenocorticotrophic hormone (ACTH) responses and biphasic fluctuations in plasma glucose were maximal at a dose of 0.05 mg/kg. HPA responses peaked between 3–5 h following immune challenge and plasma ACTH and B responses were greater in female than in male rat pups. Plasma levels of corticosterone binding globulin (CBG) were reduced in males and substantially increased in females during the peak HPA response. Changes in plasma glucose were biphasic with slight increases when ACTH and B levels were maximal, but hypoglycemia was evident once plasma B levels returned to resting values. Endotoxin challenge reduced median eminence corticotropin‐releasing hormone (CRH) levels at times corresponding with elevated HPA activity, and prior icv injection of the CRH antagonist, a‐helical CRH, significantly attenuated elevations in plasma ACTH and B. In addition, α‐helical CRH pretreatment completely blocked endotoxin‐induced changes in plasma CBG in both males and females. These findings support the view that endotoxin‐induced HPA activation in the neonate may occur via CRH.