bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional N‐Methyl‐D‐Aspartate and Non‐N‐Methyl‐D‐Aspartate Receptors are Expressed by Rat Supraoptic Neurosecretory Cells in vitro
Authors: Hu Bin , Bourque Charles W. 
Published: September 2006

AbstractA considerable amount of evidence has accumulated to support a role for excitatory glutamatergic transmission in the regulation of the hypothalamo‐neurohypophysial system. Glutamate immunoreactivity has been found in axon terminals forming asymmetric synapses on to magnocellular neurosecretory cells and kynurenic acid, a broad spectrum glutamate receptor antagonist inhibits 1) spontaneous electrical activity in vivo, 2) excitatory postsynaptic potentials in hypothalamic slices, and 3) osmotically‐evoked vasopressin release from hypothalamic explants. While this provides strong evidence for glutamatergic regulation of hypothalamic magnocellular neurosecretory cells, the subtypes of glutamate receptors expressed by these cells have not been defined. We have, therefore, obtained current and voltage clamp recordings from supraoptic magnocellular neurosecretory cells in vitro to investigate the functional and pharmacological properties of their glutamate receptors. Application of micromolar concentrations of L‐glutamate, or of the agonists kainate, quisqualate and N‐methyl‐D‐aspartate (NMDA), produced reversible and dose‐dependent depolarizations in all cells tested. These responses were mediated by postsynaptic receptors since they persisted during chemical synaptic blockade with Ca2 + ‐free or tetrodotoxin‐containing solutions. The inward current induced by NMDA showed a marked Mg2+‐sensitive voltage dependence, and was blocked by D, L‐2‐amino‐5‐phosphonovalerate. In contrast, currents induced by kainate and quisqualate showed linear current‐voltage properties and were antagonized by 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione. We conclude that both NMDA and non‐NMDA receptors are expressed by magnocellular neurosecretory cells of the rat supraoptic nucleus.
Effects of Estrous Cycle and of in vivo Unilateral or Bilateral Adrenal Demedullation on the Distribution of Norepinephrine and Epinephrine Between Different Zones of the Adrenal
Authors: Bernet François , Maubert Eric , Deloof Sylvie , Bernard Jacqueline , Montel Valerie , Dupouy Jean‐Paul 
Published: September 2006

AbstractThe distribution of norepinephrine (NE) and epinephrine (E) between the capsule/glomerular zone and the remainder of the adrenal was studied in the adult female rat. Both catecholamines were present in these two parts of the gland. The concentration of E was higher than that of NE. In the capsule/glomerular zone the catecholamine concentrations were more than twenty to thirty times lower than in the inner part of the gland. The circulating levels of catecholamines were always very low. The present data also support very weak or no changes in catecholamine concentrations in both parts of the adrenal during the different stages of the estrous cycle.The plasma levels of both aldosterone and corticosterone, like those of catecholamines, did not vary significantly throughout the estrous cycle. One week after unilateral or bilateral demedullation, both E content and concentration were reduced in the whole capsule/glomerular zone of the adrenal although the NE content did not change. The reduction of NE concentration could be related to the drastic weight increase of this part of the gland on the operated side. Moreover, unilateral demedullation was unable to significantly modify the plasma levels of both E and NE. In contrast bilateral demedullation suppressed circulating E and induced a significant reduction (about 50%) of NE plasma level. The present data suggest: 1) an extra‐adrenal origin for the NE innervation of the capsule/glomerular zone of the adrenal cortex, and 2) a dual origin for E in the capsule/glomerular zone; part of E could arise from the adrenal medulla and part from an extra‐adrenal site.
Oxytocin Excites Neurons Located in the Ventromedial Nucleus of the Guinea‐Pig Hypothalamus
Authors: Inenaga K. , Karman H. , Yamashita H. , Tribollet Eliane , Raggenbass M. , Dreifuss J. J. 
Published: September 2006

AbstractThe area of the ventromedial nucleus of the hypothalamus in the guinea‐pig was shown in autoradiographs to contain high affinity binding sites for oxytocin. In order to ascertain whether these sites may represent neuronal receptors, single‐cell extracellular recordings were obtained from ventromedial neurons in coronal slices of the hypothalamus of adult guinea‐pigs. Oxytocin applied in the nanomolar range excited about half of the neurons tested; none were inhibited. The response to the peptide was reversible and concentration‐dependent. It was exerted directly since it persisted under the condition of synaptic isolation. Moreover, the effect was specific since it could be mimicked by a selective oxytocin agonist and since vasopressin was usually at least 10‐fold weaker than oxytocin. These findings suggest that the binding sites for oxytocin detected by light microscopic autoradiography in the guinea‐pig hypothalamic ventromedial nucleus represent functional receptors.
Haloperidol Inhibits Maternal Retrieval and Licking, but Enhances Nursing Behavior and Litter Weight Gains in Lactating Rats
Authors: Stern Judith M. , Taylor Lisa A. 
Published: September 2006

AbstractTo determine whether the motorically‐active and ‐inactive components of maternal behavior in rats are differentially affected by dopamine, we administered haloperidol, a dopamine receptor antagonist, to lactating rats on day 7 (±1) post‐partum, 3 h after dam‐litter separation and 1 h before their reunion. Compared to treatment with saline or domperidone, a peripherally‐active dopamine antagonist, haloperidol treatment inhibited retrieval and licking of pups in a dose‐dependent manner and hastened the onset of nursing behavior, but impaired the high crouch posture at the highest doses (8 and 10 mg/kg). Also, litters of dams treated with 0.2, 0.4, or 1.0 mg/kg haloperidol gained almost twice as much weight as litters of controls or of dams treated with 5 to 10 mg/ kg haloperidol. To determine whether the milk ejection pattern accounts for differential litter weight gain after moderate and high doses of haloperidol, milk ejections were assessed by pup stretch and nipple‐switching responses for 30 min after the onset of crouching following a 4 h dam‐litter separation on day 12 or 13 post‐partum. The litters of dams treated with 1 or 3 mg/kg haloperidol had substantially greater litter weight gains than litters of control dams or of dams treated with 5 mg/kg haloperidol. The smaller litter weight gain of 5 mg/kg haloperidol litters was due to a retardation of milk ejections in their dams, while the smaller gain of control litters was due, at least in part, to greater behavioral activation by their dams. Non‐dopaminergic effects of large doses of haloperidol (≥5 mg/kg) may have reduced the display of the high crouching posture during nursing and contributed to the retardation of milk ejections. Thus, dopamine is necessary for the motorically‐active components of maternal behavior, but its inhibition may be necessary for the assumption of the immobile nursing postures and for maximal litter weight gains. We hypothesize that extra‐hypothalamic as well as tuberoinfundibular dopaminergic systems are inactivated by the suckling stimulus.
Ultrastructural Characteristics of Estrogen Receptor‐Containing Neurons of the Ventrolateral Nucleus of the Guinea‐Pig Hypothalamus
Authors: Silverman Ann‐Judith , DonCarlos Lydia L. , Morrell Joan I. 
Published: September 2006

AbstractThe ventrolateral nucleus of the hypothalamus (VL) of the guinea‐pig is a key cell group in the neural circuitry underlying the estrogen‐dependent lordosis reflex. The extent to which neurons in the VL are responsive to estrogen or to synaptic inputs depends in part on the presence of specific estrogen and neurotransmitter receptors within the target cells. It also depends on the number, type and location of synaptic inputs. In addition, both sensitivity to circulating hormones and transmitter responsiveness show estrogen‐inducible alterations in the VL. To understand more about the cell types that are directly modulated by estrogens via the nuclear steroid binding protein and the synaptic connectivity of these neurons, we have carried out an ultrastructural study of estrogen receptor‐containing cells in the VL of the female guinea‐pig.Estrogen receptor was localized for both light and electron microscopy using a specific monoclonal antibody, H‐222, directed against the human estrogen receptor. Numerous immunoreactive neurons were found in the VL. These cells had simple, relatively smooth dendritic processes that were generally unbranched. Reaction product was most intense in the nucleus; lighter deposits were seen in some but not all somata and proximal dendrites. No cell was observed with only cytoplasmic staining. At the ultrastructural level, this distribution of reaction product within cells was confirmed. Gold deposits were associated with euchromatin and excluded from the nucleolus, nucleolar‐associated heterochromatin and Barr body. In the cytoplasm, the small aggregates of gold particles were randomly distributed. Two types of cytologically distinct immunoreactive neurons were characterized. The most numerous category was of large cells with extensive rough endoplasmic reticulum, frequently organized as whorls or ribbons, several stacks of Golgi cisterna, numerous mitochondria and multivesicular bodies. A smaller population, representing approximately 5% of the total, was of much smaller cells which had only a thin rim of cytoplasm around the nucleus, scattered elements of the rough endoplasmic reticulum and a single small Golgi saccule. Based on size, we suggest that the larger neurons are projection neurons and that the smaller ones form local circuits. The larger cells received a dense axo‐somatic and axo‐dendritic innervation. Most of the presynaptic terminals contained small, clear round vesicles; synaptic densities on either pre‐ or postsyn‐ aptic side were absent though a well defined synaptic cleft was evident. Very few synapses were found on the small cells even when serial sections were examined. It is clear that the larger, estrogen receptor‐containing neurons are in a position to integrate both hormonal and neuronal signals and to transmit this information to other regions of the central nervous system involved in the outflow of reproductive behaviors.
In vivo Regulation of Prolactin Gene Expression in the Male Rat: Role of Sex Steroids and Dopamine
Authors: Tong Yiai , Pelletier Georges 
Published: September 2006

AbstractThe influence of sex steroids and the dopaminergic system on the in vivo modulation of prolactin (PRL) mRNA levels was investigated by quantitative in situ hybridization in the male rat anterior pituitary gland. In situ hybridization was performed using a [35S]‐labeled cDNA probe encoding PRL. Orchiectomy performed 14 days earlier did not modify PRL mRNA levels. In orchiectomized rats treatment with the dopaminergic agonist bromocriptine for 14 days decreased PRL mRNA levels by 30%, while in intact animals the same treatment did not induce any changes in PRL mRNA levels. Administration of the dopamine D2 receptor antagonist haloperidol in both intact and orchiectomized rats induced a 4‐fold increase in mRNA levels. Administration of dihydrotestosterone to orchiectomized animals which had been treated or not with haloperidol or bromocriptine did not modify PRL mRNA levels. In orchiectomized animals administration of 17ß‐estradiol (0.25 μg twice daily) for 14 days caused a 4‐fold increase in amounts of PRL mRNA. Administration of bromocriptine to 17ß‐estradiol‐treated animals induced a 15% decrease of PRL mRNA levels compared to those obtained by 17ß‐estradiol administered alone. The concomitant administration of 17ß‐estradiol and haloperidol resulted in a 50% increase in PRL mRNA levels compared to those measured in animals treated with haloperidol alone. The present results clearly demonstrate that in vivo estrogen as well as dopamine‐mediated mechanisms play a regulatory role in PRL mRNA levels in the male rat.
Afferent Stimulation Regulates Oxytocin Messenger Ribonucleic Acid During Early Lactation in Rats
Authors: Spinolo L. H. , Raghow R. , Crowley W. R. 
Published: September 2006

AbstractThe physiological factors that regulate the levels of oxytocin (OT) mRNA in the rat hypothalamo‐neurohypophyseal system during lactation are unknown. The major objective of the present studies was to test whether afferent stimuli provided by the offspring influence the level of OT mRNA in the magnocellular nuclei of the hypothalamus, i.e. the paraventricular nucleus (PVN), supraoptic nucleus (SON) and anterior commissural nucleus (ACN), during lactation. In addition, these studies provide a detailed description of the changes that occur in OT mRNA levels in these nuclei during pregnancy and lactation. Levels of OT mRNA were determined in the total RNA extracted from pooled PVN/SON/ACN, which were microdissected from pregnant and lactating Holtzman rats, by slot‐blot hybridization. RNA blots were hybridized sequentially with a [32P]5’end‐labeled, 25‐base oligonucleotide probe complementary to bases 912–936 of the OT gene and with a random primer‐labeled cDNA complementary to α‐tubulin mRNA, which was used for normalization. Autoradiographs were quantitated by scanning laser densitometry. Compared to the levels on day 1 of pregnancy (the day of mated estrus) the relative levels of OT mRNA were decreased on pregnancy days 7 and 14, and then returned to the mated estrus value on days 16 to 20. The level of OT mRNA again declined prior to parturition on day 23, although it was restored to the estrus value the day after parturition and generally remained at this level throughout lactation. To assess the influence of stimuli provided by the offspring for the regulation of OT mRNA levels during lactation, lactating females were separated from their litters immediately after parturition or on lactation day 8. As compared to nonseparated, time‐matched controls, removal of the litters immediately after parturition resulted in a statistically significant reduction of approximately 25% in the levels of OT mRNA 24 and 48 h later, which returned to control levels by 72 h. In contrast, removal of the litters on lactation day 8 did not significantly alter the level of OT mRNA in the PVN/SON/ACN over the next 3 days. These findings suggest that the level of OT mRNA in hypothalamic magnocellular nuclei is influenced to some extent by afferent stimuli provided by the offspring during an early period of lactation but, thereafter, becomes unresponsive to removal of this influence. Afferent suckling stimuli may be one component of a multifactorial regulation responsible for the maintenance of OT mRNA expression during lactation.
Functionally and Anatomically Distinct Populations of Vasopressinergic Magnocellular Neurons in the Female Golden Hamster
Authors: Ferris Craig F. , Pilapil Carmencita G. , Hayden‐Hixson Diane , Wiley Ronald G. , Koh Edward T. 
Published: September 2006

AbstractThe present study was done to determine whether the vasopressinergic neurons in the hypothalamus controlling flank marking behavior are distinct from the magnocellular neurons comprising the hypothalamo‐neurohypophysial system. Animals were either hypophysectomized or injected with a suicide transport lectin, volkensin, into the neurohypophysis. Both procedures resulted in a pronounced loss of vasopressin‐immunoreactive perikarya throughout the hypothalamus concomitant with increases in water intake and urine output and decreases in circulating levels of vasopressin. The loss of the hypothalamo‐neurohypophysial system was most pronounced in volkensin‐treated animals that presented with frank diabetes insipidus and exceedingly low levels of plasma vasopressin. However, the vasopressinergic fibers and magnocellular neurons in and around the anterior hypothalamus implicated in the control of flank marking survived the volkensin treatment. Volkensin‐treated animals exhibited levels of flank marking typical of untreated animals. These data suggest the presence of anatomically and functionally distinct populations of vasopressinergic magnocellular neurons in the hypothalamus of the golden hamster.
Cerebral Metabolic and Vasopressin and Oxytocin Responses During Osmotic Stimulation in Conscious Rats
Authors: Kadekaro Massako , Summy‐Long Joan Y. , Harris Jennifer S. , Terrell Mary Lee , Freeman Sondra , Eisenberg Howard M. 
Published: September 2006

AbstractIntravenous infusion of hypertonic saline increased plasma [Na +] and osmolality and induced a short‐latency drinking response. These changes were associated with increased glucose utilization in the supraoptic and paraventricular nuclei and neural lobe, and decreases in the medial septum and nucleus ambiguus. The increases in glucose utilization were more accentuated in the supraoptic nuclei than in paraventricular nuclei, indicating that they are more sensitive to osmotic stimulation than the paraventricular nuclei. In association with enhanced activity in the hypothalamo‐neurohypophysial system, plasma vasopressin and oxytocin concentrations increased, with a preferential increase of oxytocin over vasopressin. The hormonal contents in the neural lobe were not depleted by the osmotic stimulus despite the large increases of their concentrations in the plasma.
Inhibition of Luteinizing Hormone Secretion in the Ewe by Progesterone: Associated Changes in the Release of Gamma‐Aminobutyric Acid and Noradrenaline in the Preoptic Area as Measured by Intracranial Microdialysis
Authors: Robinson Jane E. , Kendrick Keith M. 
Published: September 2006

AbstractProgesterone inhibits the pulsatile release of luteinizing hormone (LH) in sheep by an action in the brain to suppress the release of LH‐releasing hormone (LHRH). In addition, progesterone blocks the preovulatory surge of LH in this species. The neural basis of this inhibitory action is unknown, but as LHRH cells do not appear to contain progestin receptors other neural systems must mediate the action of this ovarian steroid on LH release. This study focuses on a possible role for the inhibitory amino‐acid GABA and the monoamines (noradrenaline, adrenaline, dopamine and serotonin). The technique of microdialysis was used to monitor changes in these substances in the vicinity of the LHRH cell bodies (in the preoptic area) both before and following the administration of progesterone. Levels of this steroid, similar to those measured during the mid‐luteal phase of the oestrous cycle, inhibited LH release and this was associated with significant alterations in the release of GABA and noradrenaline (but not adrenaline, dopamine or serotonin). Specifically, progesterone augmented GABA while noradrenaline release was depressed. Whether steroid actions on these neurotransmitters were mediated by opioids was also investigated. This possibility arises because of the reported involvement of opioids in progesterone negative feedback in the ewe. The long‐acting opioid antagonist, naltrexone, was administered and GABA and noradrenaline release monitored for a further period both in the presence and absence of progesterone. Naltrexone significantly depressed GABA release in steroid‐treated (but not untreated) ewes suggesting that the actions of progesterone on GABA are mediated by the endogenous opioid peptides. However, noradrenaline release was unaltered. In an earlier study we demonstrated that GABA release fell prior to the LH surge while noradrenaline release increased. These data, in conjunction with those from the present study, suggest that the mechanism by which progesterone is able to inhibit the preovulatory surge of LH in the ewe is by enhancing GABA and depressing noradrenaline release in the vicinity of the LHRH cell bodies. As opioid tone is also reported to fall prior to the surge, the interaction between opiate and GABAergic systems in the regulation of gonadotrophin secretion warrants further investigation.
A Rat Pituitary Tumour K+ Channel Expressed in Frog Oocytes Induces a Transient K+ Current Indistinguishable from that Recorded in Native Cells
Authors: Meyerhof Wolfgang , Schwarz Jürgen R. , Bauer Christiane K. , Hübel Andreas , Richter Dietmar 
Published: September 2006

AbstractA voltage‐gated K+ channel protein has been cloned from a cDNA library derived from poly(A)+ RNA of the rat pituitary tumour cell line GH3/B6 by the polymerase chain reaction technique. The clone referred to as RGHK9 encodes a protein sequence very similar to a recently cloned K+ channel protein from rat brain and heart, with deviations in a few amino‐acid positions. In situ hybridization experiments show that RGHK9 mRNA is also present in the anterior pituitary as well as in other brain regions and that it is particularly abundant in the hippocampus. After injection of cRNA transcribed from the RGHK9 cDNA clone into Xenopus oocytes, the expressed protein induces a transient K+ current. Except for the activation kinetics the properties of this current are indistinguishable from that of the native transient K+ current measured in GH3/B6 cells, e.g. both K+ currents are blocked by 4‐aminopyridine and show the same voltage dependence and slope of steady state activation and inactivation as well as identical time constants of, and slow recovery from, inactivation. Taken together, these data show that the outward‐rectifying voltage‐gated K+ channel protein encoded by the RGHK9 cDNA correlates well in its functional properties with that of a very similar, if not identical, K+ channel present in GH3/B6 cells.
Melatonin Binding Sites in the Ovine Brain and Pituitary: Characterization During the Oestrous Cycle
Authors: Heiliwell Rachel J. A. , Williams Lynda M. 
Published: September 2006

AbstractThe distribution of putative melatonin receptors in the sheep has been investigated using in vitro autoradiography and the high affinity, high specific activity ligand 2‐[125l]iodomelatonin. A wide distribution of specific labelling was found in both the ovine brain and pituitary gland as previously reported. Several novel areas of binding were also identified in the present study, including a fine layer of labelling at the medial edge of the diagonal band of Broca, the trigeminal nucleus, laminae II and III of the substantia gelatinosa, the molecular layer of the cerebellum as well as a scattered labelling in the pars distalis of the pituitary. There was no evidence of specific labelling in any of the peripheral tissues examined.Characterization studies performed on both neuronal and pituitary melatonin binding sites revealed that binding was time‐ and temperature‐dependent and reversible on addition of 1 μM melatonin. The binding of 2‐[125l]iodomelatonin was also competitively inhibited by increasing concentrations of 2‐iodomelatonin and melatonin. The inhibition constants (Ki) estimated for each of these substances were similar for both neuronal and pituitary sites. Saturation studies also revealed similarities between neuronal and pituitary tissues with 2‐[125l]iodomelatonin binding specifically to a single class of high affinity binding sites. Values for equilibrium constants (Kd) were within a range of 28 to 48 pM, and values were found to be not significantly different amongst the four regions of the brain investigated and the pars tuberalis of the pituitary. In contrast, the concentration of 2‐[125l]iodomelatonin binding sites (Bmax) ranged from 3 to 218fmol/mg protein and were maximal for the pars tuberalis.Saturation studies on brain and pituitary tissues taken from ewes killed either on the day of oestrus or during the luteal phase of the oestrous cycle, indicated that no differences exist in the affinity or concentration of 2‐[125l]iodomelatonin binding in any region between the two times of the cycle investigated.