bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Novelty Stress on Vasopressin and Oxytocin Secretion by the Pituitary in the Rat
Authors: Onaka Tatsushi , Yagi Kinji 
Published: September 2006

AbstractEffects of novel environmental stimuli on vasopressin and oxytocin secretion by the pituitary were studied in dehydrated male rats. As the novel environmental stimuli, rats were transferred to an experimental room, placed in a box painted black and given a pure tone auditory stimulus of 2 kHz. Exposure of rats to the novel environmental stimuli for a period of 2 min decreased plasma concentrations of vasopressin and increased plasma levels of adrenocorticotrophic hormone (ACTH) and prolactin, but did not significantly change the plasma level of oxytocin. The stimuli, however, became ineffective for producing the suppressive vasopressin response as the period of exposure was prolonged to more than 5 and up to 30 min, although the prolonged stimuli were still effective for inducing facilitatory ACTH and prolactin responses. After repeated exposures of rats to the environmental stimuli once a day for 5 or 10 days, the stimuli became disabled from producing the suppressive vasopressin response. However, the rats were still capable of responding to the novel stimuli of another kind. All these data suggest that novelty stress suppresses vasopressin secretion but does not change oxytocin secretion. In order to test the possibility that glucocorticoids expectedly secreted by the adrenals in response to the stress might have suppressed vasopressin secretion, a large amount of dexamethasone was administered to the rat before testing. Dexamethasone pretreatment depressed plasma levels of ACTH and vasopressin as reported previously and blocked the facilitatory ACTH response to the novelty stress. However, dexamethasone treatment did not affect the suppressive vasopressin response to the novelty stress. Thus, it is likely that the suppressive vasopressin response to novelty stress does not primarily depend upon endogenous glucocorticoids.
Hypothalamic Neuropeptide Y Messenger Ribonucleic Acid Levels in Pre‐Obese and Genetically Obese (fa/fa) Rats; Potential Regulation Thereof by Corticotropin‐Releasing Factor
Authors: van Huijsduijnen OlfaBchini‐Hooft , Rohner‐Jeanrenaud Françoise , Jeanrenaud Bernard 
Published: September 2006

AbstractNeuropeptide Y (NPY) is a 36 amino‐acid peptide. It is localized within the brain but is also present peripherally. It is a well substantiated orexigenic peptide with several other endocrine and behavioural effects. In this study NPY mRNA levels were measured, using the polymerase chain reaction amplification technique, in the hypothalamus of pre‐obese (unweaned 13‐day‐ old), young (weaned 28‐day‐old) and adult (11‐week‐old) obese fa/fa rats and compared to those of lean age‐matched controls. Before weaning, pre‐obese pups had the same NPY mRNA levels as controls. After weaning NPY mRNA levels were increased 2‐fold in young 28‐day‐old and 4‐fold in adult obese rats, relative to corresponding controls. When adult obese rats were intracerebroventricularly‐treated with ovine corticotropin‐releasing hormone (oCRF) for 7 days, they stopped gaining body weight elative to vehicle‐infused obese controls. Upon measuring NPY mRNA levels in the hypothalamus of these two groups of animals, it was shown that the high NPY mRNA levels of vehicle‐treated (control) obese rats were decreased by 3‐fold following the intracerebroventricular oCRF administration. It is proposed that: 1) hypothalamic NPY may play a role in the establishment and maintenance of the genetic obesity syndrome of the fa/fa rat, and 2) hypothalamic NPY could be partly regulated by central CRF.
The Actions of Endothelin on Single Cells in the Anteroventral Third Ventricular Region and Supraoptic Nucleus in Rat Hypothalamic Slices
Authors: Yamamoto Shigeki , Inenaga Kiyotoshi , Kannan Hiroshi , Eto Sumiya , Yamashita Hiroshi 
Published: September 2006

AbstractEndothelin (ET), a peptide consisting of 21 amino‐acid residues was recently isolated from the culture supernatant of porcine aortic endothelial cells. ET has been reported to be a more potent vasoconstrictor than angiotensin II. Other studies suggest that ET is involved in central control of the autonomie nervous system and body water regulation. Extracellular recordings were made from neurons in the anteroventral third ventricle (AV3V) and supraoptic nucleus (SON) in rat hypothalamic slice preparations. ET‐3 was applied at concentrations of 10−10 M to 3x 10−7 M. Of 226 AV3V neurons tested, 48 (21%) were excited, 8 (4%) were inhibited, and 170 (75%) were unaffected by ET‐3 at 10−7 M. The threshold concentration to evoke the responses was approximately 10−9 M. Of 144 SON neurons tested, 64 had a phasic firing pattern and 80 had a non‐phasic firing pattern. Of 64 phasic neurons tested, 39 (61%) were inhibited by ET‐3 at 10−7 M, 25 (39%) were non‐responsive and none was excited. Of 80 non‐phasic neurons tested, 14 (17.5%) were inhibited by ET‐3 at 10−7 M, 66 (82.5%) were non‐responsive and none was excited. The effects of ET‐1 were compared with those of ET‐3. The number of neurons responding to ET‐1 and their responsiveness were almost the same as for ET‐3. To investigate whether the ET responses are dependent on Ca2+ influx, a Ca2+ free medium and the Ca2+ antagonist, nicardipine, were used. The excitatory responses of AV3V neurons to ET were maintained in the Ca2+ free medium. Nicardipine at 10−5 M suppressed neither the excitatory responses of AV3V neurons nor the inhibitory responses of SON neurons to ET‐3. After 8 to 12 h preincubation of slices with islet activating peptide (IAP: pertussis toxin) at 10−7 M, none of the 48 AV3V neurons tested was excited by either ET‐3 or ET‐1. On the other hand, inhibitory responses were still observed in 12 (52%) out of 23 phasic SON neurons tested after IAP treatment. These results suggest that ET has a direct action as a neuropeptide on hypothalamic neurons through the ETB receptor and that the mechanisms underlying the responses may be different in the AV3V and the SON.
Activation of Magnocellular Vasopressin Responses to Non‐Osmotic Stress After Chronic Adrenal Demedullation in Rats
Authors: Aguilera Greti , Kiss Alexander 
Published: September 2006

AbstractIncreases in plasma VP in response to osmotic stimulation are critical for water conservation, while VP released into the pituitary portal circulation is an important regulator of ACTH secretion and does not contribute to plasma VP levels. The role of the adrenal medulla in the specificity of these responses was studied in rats subjected to osmotic and non‐osmotic stress two months following adrenal demedullation or sham operation. Basal and stimulated plasma corticosterone, aldosterone, ACTH and PRA levels in adrenal demedullated rats were similar to those in the sham operated groups indicating recovery of adrenocortical function. Basal plasma VP levels were similar in sham operated controls and adrenal demedullated rats (0.93±0.13 and 1.0 ± 0.1 pg/ml, respectively) and rose to comparable levels in both groups following 48 h osmotic stimulation by water deprivation (14.4+1.3 and 20.7 + 3.4, respectively). On the other hand, while in sham operated rats, immobilization for 15 min, a non‐osmotic stress, had no effect on plasma VP levels in control or water deprived (2.0±0.9 and 15.0±2.7 pg/ml), in adrenal demedullated rats, caused dramatic increases in plasma VP from 1.0±0.1 to 126.0 + 29.9 pg/ml in controls, and from 20.7 + 3.4 to 155 + 37 pg/ml in water deprived rats. Intraperitoneal hypertonic saline injection, a combination of osmotic and painful stress, caused much higher increases in plasma VP in adrenal demedullated rats (138.0 + 22.1 compared with 34.7 + 3.7 pg/ml in sham operated rats). Water deprivation potentiated this response to 70.0 + 8.3 and 295 + 24 pg/ml in sham operated and adrenal demedullated rats, respectively. VP mRNA measured by in situ hybridization, and irVP measured by immunohistochemistry, were elevated in magnocellular neurones in the hypothalamus of adrenal demedullated rats. The demonstration of marked plasma VP responses to non‐osmotic stimuli in adrenal demedullated rats, suggests a modulatory role for the adrenal medulla in the specificity of the secretory responses of the magnocellular and parvicellular vasopressinergic systems.
Vasopressin Anti‐Idiotypic Antibody Staining in the Rat Brain: Colocalization with [35S][pGlu4, Cyt6]AVP(4–9) Binding Sites
Authors: Jurzak M. , Fahrenholz F. , Gerstberger R. 
Published: September 2006

AbstractVasopressin and its fragment peptides such as [pGlu4, Cyt6]AVP(4–9) (AVP(4–9)) represent putative neuromodulators within central nervous homeostatic, memory and behavioural circuits. To localize their central receptor systems, the previously characterized monoclonal anti‐idiotypic antibody mAb 237 was employed in immunocytological investigations of rat brain tissue sections. This antibody was raised to the monoclonal idiotypic anti‐AVP antibody mAb 113 which preferentially binds to the acyclic C‐terminal portion of the AVP molecule and is therefore also capable of binding the naturally occurring AVP(4–9) fragment. Immunoreactive magnocellular neurones were detected in the AVP‐synthesizing supraoptic but not paraventricular nuclei. Dense staining was observed within circumventricular organs lacking a blood‐brain barrier (BBB). These structures include the subfornical organ, the organum vasculosum laminae terminalis, the internal layer of the median eminence, the body of the pineal gland, the choroid plexus and the area postrema, where immunoreactivity was found on capillaries, neurones and fibres. Further staining was found in the nucleus of the solitari tract and the arcuate nucleus, endowed with a leaky BBB. Distinct cell patches in the ependymal lining of the third ventricle as well as dendritic processes of juxtaependymal neurones were labelled by the anti‐idiotypic antibody mAb 237. The observed staining pattern did not parallel that obtained in autoradiographic studies performed using either radiolabelled AVP or a V1‐receptor antagonist, but that found with the [35S]‐labelled AVP(4–9) fragment. Using [35S]‐labelled AVP(4–9) fragment, specific high density binding sites could be localized autoradiographically in structures within and outside the BBB, in complete agreement with the anti‐idiotypic immunoreactivity.Since the anti‐idiotypic methodology is based on transfer of complementary structures, and the epitope recognized by the corresponding idiotypic antibody resembles the sequence of AVP(4–9), the anti‐idiotypic antibodies might recognize the AVP(4–9) receptor with high affinity.
Neurons in the Paraventricular Nucleus of the Hypothalamus that Project to the Sexually Dimorphic Lower Lumbar Spinal Cord Concentrate 3H‐Estradiol in the Male Rat
Authors: Wagner Christine K. , Sisk Cheryl L. , Clemens Lynwood G. 
Published: September 2006

AbstractThe location and distribution of estradiol‐concentrating neurons in the hypothalamus afferent to segments of lumbar spinal cord that contain the sexually dimorphic spinal nucleus of the bulbocavernosus (SNB) were determined by combining retrograde fluorescent tract tracing with steroid hormone autoradiography. Injections of Fluorogold were made into segments of L5‐L6 of the spinal cord of adult male rats and 12 days later animals were castrated. One week following castration, males received injections of [3H]estradiol and were perfused. Their brains were then processed for steroid hormone autoradiography. Following exposure times of 11 to 12 months, autoradiograms were developed and the hypothalamus was analyzed for neurons that concentrate estradiol and project to the spinal cord.Numerous neurons in the hypothalamus projected to the spinal cord, specifically neurons in the paraventricular nucleus (PVN), the lateral hypothalamus and the dorsal area of the hypothalamus. Although many subnuclei of PVN, as well as lateral hypothalamus, contained Fluorogold labelled neurons and estradiol concentrating neurons, the majority of double labeled cells were found in the lateral parvocellular (lp) subnucleus of PVN. Approximately 30% of the neurons in the lp subnucleus that projected to spinal cord also concentrated estradiol. Up to one half of the estradiol‐concentrating neurons in Ip sent axons to the lower lumbar spinal cord. These results suggest that some of the effects of gonadal steroid hormones on SNB development, plasticity and function may in fact, be indirect, via steroid‐sensitive afferents.
Electrophysiological Effects of Pressure‐Ejected Bombesin‐Like Peptides on Hamster Suprachiasmatic Nucleus Neurons in vitro
Authors: Piggins Hugh D. , Rusak Benjamin 
Published: September 2006

AbstractThe suprachiasmatic nuclei (SCN) of the rodent hypothalamus function as a light entrainable circadian pacemaker. The SCN contain moderate to high concentrations of a number of neuropeptides including peptides showing structural homology with the amphibian derived tetradecapeptide, bombesin (BN), called bombesin‐like peptides (BNLPs). BNLPs include the 27 amino acid peptide, gastrin releasing peptide (GRP,1–27), a smaller decapeptide (GRP18–27) and another decapeptide with less structural homology, neuromedin B (NmB). Immunoreactivity for BN and receptors for BNLPs have been demonstrated in the region of the rat SCN receiving photic input. We studied the effects of local pressure ejections of BNLPs dissolved in saline/1% bovine serum albumin (BSA) vehicle on the extracellularly recorded firing rates of Syrian hamster SCN neurons in a hypothalamic slice preparation. In one study, an ejecting electrode containing BN (10−8 to 10−4 M) was positioned 20 to 60 μm from a recording electrode. Of 74 cells tested with BN, 50 (67.6%) showed significant increases in firing rate, while 3 of 19 cells (15.8%) tested with vehicle ejections were activated. In a second study, a single electrode was used for both recordings and pressure ejections. Of 48 cells tested, BN (10−6 to 10−4 M) activated 30 (62.5%) and suppressed firing in 4 (8.3%). Of 208 cells tested with GRP1–27 (10−9 to 10−4 M), 105 (50.5%) were activated and 2 (1.0%) were suppressed. The percentage of cells responding increased with the concentration of GRP1–27 used in the electrode. No circadian variation in responsiveness to GRP1–27 was detected. GRP18–27 (5 ± 10−5 to 10−4 M) activated 10 out of 18 cells tested (55.6%), while NmB (10−4 M) activated 2 out of 30 cells tested (6.7%) and vehicle ejections activated 1 out 36 cells tested (2.8%). GRP1–27, GRP18–27 and BN, the BNLPs showing the greatest degree of structural homology, activate ∼50% of SCN cells, apparently via the BN/GRP‐preferring receptor subtype, and may play a role in photic entrainment.
Dynorphin 1–17 Delays the Vasopressin Induced Mobilization of Intracellular Calcium in Cultured Astrocytes from the Rat Neural Lobe
Authors: Boersma C. J. C. , Van Leeuwen F. W. , O'Brien W. G. , Law G. J. , Mason W. T. , Bicknell R. J. 
Published: September 2006

AbstractOpioid peptides are present in nerve terminals in the rat neural lobe where they partially coexist with vasopressin. Morphological findings suggest that these neuropeptides are released onto pituicytes, which is in agreement with a possible role for the pituicyte in oxytocin and vasopressin release from the neural lobe.Pituicytes in culture respond to vasopressin with a mobilization of calcium from intracellular stores. In the present study this vasopressin induced increase in intracellular free calcium levels was both delayed and decreased by pre‐exposure to dynorphin 1–17, while dynorphin 1–17 by itself did not affect basal calcium levels. All effects of dynorphin 1–17 could be blocked with naloxone. The present results suggest that opioid receptors are present on pituicytes and are coupled to a second messenger pathway by which opioid peptides may inhibit inositol phosphate dependent calcium mobilization by other neuropeptides, such as vasopressin.
Immunocytochemical and Biochemical Evidence for Aromatase in Neurons of the Retina, Optic Tectum and Retinotectal Pathways in Goldfish
Authors: Gelinas Danielle , Callard Gloria V. 
Published: September 2006

AbstractUsing an animal model in which neural aromatase is apparently overexpressed (the goldfish, Carassius auratus) and an antihuman placental antibody which specifically crossreacts with goldfish brain aromatase, aromatase‐immunoreactive neuronal cell bodies and fibers have been localized within the retina. These include a subset of horizontal cells, bipolar cells, and amacrine cells of the inner nuclear layer, some fibers of the outer and inner synaptic layers and certain cells of the ganglion cell layer; photoreceptors were never labeled. Some ganglion cell projections to the brain via the optic nerve and optic tract were aromatase‐positive, as were small neurons of the stratum periventriculare (SPV) and fibers of two other strata of the optic tectum. Aromatase activity, as measured by [3H]estrogen formation from [3H]androgen by tissue homogenates and cell cultures, confirmed the presence of aromatase in retina and in brain regions containing the optic tectum. This localization of the rate‐limiting enzyme in estrogen biosynthesis suggests that neuroestrogen derived from circulating androgen may modulate transmission and integration of visual information important for reproduction in this species.
Effects of Excitatory Amino Acid Receptor Agonists and Antagonists on the Secretion of Melatonin, Luteinizing Hormone and Prolactin in the Ram
Authors: Kumar V. , Lincoln G. A. , Tortonese D. J. 
Published: September 2006

AbstractTo assess the role of excitatory amino acids (EAA) as neurotransmitters in the transmission of light information from the retina to the pineal gland, we have determined whether the systemic injection of EAA agonists in Soay rams will mimic the suppressive effect of light on the secretion of melatonin, and whether pretreatment of rams with EAA antagonists will block this effect. In addition, the efficacy of the drugs in affecting neuroendocrine systems was investigated by measuring the changes in the secretion of luteinizing hormone (LH) and prolactin.Injections of the EAA receptor agonist, NMDA (N‐methyl‐D,L‐aspartate: 4.0 mg/kg iv), and the non‐NMDA type EAA receptor agonist, AMPA (DL‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐propionic acid : 0.2 mg/kg iv) given at night to rams exposed to long days (16 h light:8 h darkness), caused no change in the blood plasma concentrations of melatonin. The treatments induced an acute increase in the concentrations of LH, and NMDA, but not AMPA, caused a sustained increase in the concentrations of prolactin. Injections of the specific NMDA‐type receptor antagonist, CGP (CGP 37849: 1.0 mg/kg iv) and the non‐NMDA‐type receptor antagonist, DNQX (6,7 Dinitroquinoxaline‐2,3‐dione: 0.5 mg/kg iv), given prior to a 1‐h light period at night, in rams under long days, caused no change in the light‐induced decrease in blood plasma concentrations of melatonin. The drug treatments had no effect on the plasma concentrations of LH, but CGP, and not DNQX, stimulated an acute increase in the plasma concentrations of prolactin.These results provide support for the hypothesis that EAA mechanisms operate in the hypothalamus to regulate the release of peptides and catecholamines which control the secretion of LH and prolactin from the pituitary gland; different sub‐types of EAA receptors are involved in the control of the two pituitary hormones. The failure of the treatments to affect the secretion of melatonin may indicate that EAA receptor activation is not involved in the photic relay to the pineal gland, or may merely reflect the inability of the drugs to penetrate into the retina/SCN/pineal neural circuits to produce a response.
Facilitation and Feedback in the Hypothalamo‐Pituitary‐Adrenal Axis during Food Restriction in Rats
Authors: Garcia‐Belenguer Sylvia , Oliver Charles , Morméde Pierre 
Published: September 2006

AbstractAfter 4 weeks of food restriction to 50% of ad libitum intake in rats, plasma corticosterone levels were increased, without any change in adrenal weight, and with no evidence of sympathetic nervous system activation (as measured by Tyrosine Hydroxylase and Phenylethanolamine N‐Methyl Transferase activities in the adrenal gland). Plasma corticosterone levels were normalized with the addition of 35% of the calories as sugar. The adrenocortical axis activity was therefore investigated in more detail (nycthemeral cycle of corticosterone levels, ACTH and corticosterone response to a CRF challenge) in ad libitum fed rats and in animals fed 85% or 50% of the intake of the control animals, just before switching the lights off in order to maintain the diurnal rhythm of food intake. Food restriction to 85% did not change mean plasma corticosterone levels but sharpened the peak of corticosterone measured in the evening, indicating that the adrenocortical axis is more sensitive to the endogenous signals responsible for its diurnal cycle of activity. Indeed, the ACTH response to CRF was also increased. A 50% food restriction regimen increased mean corticosterone levels and attenuated the day/night difference, with high corticosterone levels maintained throughout the day. However, the ACTH response to CRF was not different from that measured in ad libitum fed rats, but the corticosterone response was lower, confirming that the adrenal gland is hyposensitive to ACTH. The results are discussed in terms of the balance between inhibiting/activating mechanisms and endocrine/neural influences at each level of the hypothalamo‐hypophyso‐adrenal axis, depending on the level of food deprivation.
Identification and Localization of 23,000 and Glycosylated Rat Prolactin in Subcellular Fractions of Rat Anterior Pituitary and Purified Secretory Granules
Authors: Bollengier F. , Geerts A. , Matton A. , Mahler A. , Velkeniers B. , Hooghe‐Peters E. , Vanhaelst L. 
Published: September 2006

AbstractRat pituitary homogenates were submitted to differential and density gradient centrifugation. Subcellular fractions as well as the purified secretory granules were examined in electron microscopy, radioimmunological techniques, protease digestion, alkaline treatment and immunoblotting.The global outcome of these experiments was that: 1) the glycosylated rPRL was foremost recorded in the crude secretory granular fraction, also in the microsomal fraction and the cytosol, but virtually not in the plasma membrane fraction; 2) in purified secretory granules glycosylated rPRL appeared as an array of near Mr, such as was formerly obtained by enzymatic deglycosylation; 3) protease digestion and ice‐cold alkaline treatment of the secretory granules showed that 23,000 rPRL appears in three different physicochemical states in these organelles: unsequestered within a closed system, membrane‐bounded and membrane‐bound, whereas glycosylated rPRL preferentially assumed the membrane‐bounded and bound state; 4) likewise treatment of microsomal vesicles showed that 23,000 and glycosylated rPRL are sequestered in these bodies, but apparently 23,000 rPRL appears as both integral membrane‐bound and released from the lumen, whereas glycosylated rPRL is chiefly retained as an integral membrane protein. 5) dopamine alters the pattern of glycosylation as well in Mr as in relative percentages of the molecular variants.The systematical occurrence of the array of near Mr glycosylated rPRL variants in secretory granules and microsomal vesicles strongly indicates that glycosylated rPRL is biosynthesized as a pool of proteins with a different degree of glycosylation. On the basis of our data, we speculate that selection of definite molecular variants from this pool could play an important role in the biological function of 23,000 rPRL and that oligosaccharides could perhaps target the glycosylated forms of rPRL to specific sites of action.