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PubMed1986

Contributions of glomerular and tubular mechanisms to antidiuresis in conscious domestic fowl.

Recently developed radioimmunoassay (RIA techniques were employed in a quantitative investigation of the renal actions of the avian antidiuretic hormone arginine vasotocin (AVT) in the conscious domestic fowl. Constant intravenous infusion of AVT at doses of 0.125-1.00 ng . kg-1 . min-1 was used to produce plasma AVT (PAVT) concentrations (verified by RIA) over the entire range of physiological PAVT levels in the domestic fowl. Comparison of the dose-response relationships between PAVT and glomerular and tubular mechanisms of antidiuresis revealed that tubular mechanisms are of primary importance and glomerular mechanisms of secondary importance in the conservation of water by the avian kidney. The greatest proportion of the total AVT-induced reduction in renal water excretion occurred at low physiological PAVT levels (less than 5 microU/ml), prior to any significant reduction in glomerular filtration rate (GFR), and appeared to be the exclusive result of tubular mechanisms of antidiuresis. At high PAVT levels (5-16 microU/ml), glomerular and tubular mechanisms overlapped, and their effects on water conservation could not be separated. Although GFR was reduced by nearly 30% at the highest dose of AVT, only minor additional amounts of water were conserved by the combined actions of glomerular and tubular mechanisms. The glomerular mechanisms appear to have only a minor secondary effect on water-conserving ability of the avian kidney.

Animals↗

PubMed1976

Variation in the effects of antidiuretic hormone on the isolated skin of the toad, Scaphiopus couchi.

The rate of active sodium transport as measured by short-circuit current across the isolated skin of the toad, Scaphiopus couchi, was elevated following vasopressin (0.2 units/ml) or arginine vasotocin (0.1 units/ml) treatment of skins from active animals at all times of the year tested. Skins from dormant animals showed no such elevation at any time of the year. The rate of active sodium transport was elevated following treatment with dibutyryl cyclic AMP (2.5mM) plus theophylline (10 mM) in all skins tested. The hydraulic conductivity of isolated skins from both active and dormant animals showed no significant change following treatment with vasopressin (0.2 units/ml) or arginine vasotocin (0.1 units/ml except on the first day following emergence from dormancy in the field. A correlation was, therefore, observed between the occurrence of a hydroosmotic response to antidiuretic hormones and the seasonal exposure of S. couchi to standing water. A small but significant elevation of hydraulic conductivity was observed across the skins of dormant toads following treatment with dibutyryl cyclic AMP (2.5 mM) plus theophylline (10 mM) whereas a substantial elevation was observed with the skins of active animals.

Animals↗

PubMed1984

Immunohistochemistry of the hypothalamic neuropeptides and anterior pituitary cells in the Japanese quail.

The pars distalis of the avian adenohypophysis consists of well-defined cephalic and caudal lobes which are distinct in their cellular constituents. Immunocytochemical investigations on the pituitary hormones of the pars distalis of the Japanese quail reveal five types of secretory cells, adenocorticotropin (ACTH) cells, prolactin (PRL) cells, thyroid-stimulating hormone (TSH) cells, growth hormone GH (STH) cells, and FSH/LH (gonadotropic) cells. The ACTH cells, TSH cells, and PRL cells are restricted to the cephalic lobe, and GH (STH) cells are confined to the caudal lobe, while FSH/LH cells are distributed throughout the cephalic and caudal lobes. The median eminence of birds has distinct anterior and posterior divisions, each with different neuronal components. The avian hypophysial portal vessels also consists of two groups, anterior and posterior. The peculiar arrangement and distribution of the avian hypophysial portal vessels are possibly related to the distribution of neuropeptides in the two divisions of the median eminence and to the cytological and functional differentiation of two lobes of the pars distalis. The localization of perikarya and fibers containing luteinizing hormone releasing hormone (LHRH), somatostatin, vasotocin, mesotocin, corticotropin-releasing factor (CRF), vasoactive intestinal polypeptide (VIP), glucagon, metenkephalin, and substance P in the hypothalamus and median eminence of the Japanese quail has been investigated by means of immunohistochemistry using antisera against the respective neuropeptides. LHRH-, somatostatin-, VIP-, met-enkephalin-, and substance P-immunoreactive fibers are localized in the external layer of the anterior and posterior divisions of the median eminence, while CRF- and vasotocin-reactive fibers are demonstrated only in the external layer of the anterior division of the median eminence. The metenkephalin fibers are thicker in the anterior median eminence but the substance P fibers are more abundant in the posterior division. Mesotocin fibers occur only in the internal layer of the median eminence and neural lobe.

Adrenocorticotropic Hormone↗

PubMed2002

Functional analysis of natriuretic peptide receptors in the bladder of the toad, Bufo marinus.

This study aimed to localize and characterize natriuretic peptide binding sites in the urinary bladder of Bufo marinus and to then examine the effect of natriuretic peptides on the bladder vascular tone and water reabsorption in isolated perfused bladder preparations. Specific (125)I-rat atrial natriuretic peptide ((125)I-rANP) binding sites were present on blood vessels, muscle, and epithelium. In tissue sections and/or isolated membranes, the binding was completely displaced by frog ANP, rat ANP, and porcine C-type natriuretic peptide (CNP; membranes only). However, a reduction in binding was observed after incubation with (125)I-rANP and 1 microM of the natriuretic peptide receptor-C (NPR-C) ligand C-ANF, but residual binding remained suggesting the presence of two distinct binding sites. Electrophoresis of bladder membranes cross-linked to (125)I-rANP identified two bands at approximately 70 and 140 kDa that correspond to the monomeric mass of NPR-C and the guanylate cyclase receptors, respectively. Furthermore, the presence of natriuretic peptide receptor-A and NPR-C mRNA in the bladder was demonstrated with reverse transcription--polymerase chain reaction. In addition, rat ANP, frog ANP, and porcine CNP stimulated a significant increase in cGMP generation in bladder membrane preparations, which indicated the presence of guanylate cyclase-linked receptors. In perfused bladder preparations, arginine vasotocin increased perfusion pressure and water permeability. The infusion of frog ANP or porcine CNP failed to alter perfusion pressure or water reabsorption in the presence or absence of arginine vasotocin. This study identified a well-developed natriuretic peptide receptor system in the urinary bladder of B. marinus but the function of the receptors remains unclear.

Absorption↗

PubMed1978

Immunocytochemical identification of an LHRH-producing system originating in the preoptic nucleus of the duck.

A fluorescent technique applying specific LHRH and vasotocin antisera was used for the immunocytochemical localization of the respective neurosecretory systems in the hypothalamus of gonadectomized, testosterone-treated and/or serotonin injected male domestic ducks. An immunoreactive (IR) LHRH-producing system, with perikarya located in the preoptic nucleus, could be traced through the ventral hypothalamus down to the external layer of the rostral and caudal ME, in close vicinity to the hypophysial portal system. An IR-vasotocin system originating in the paraventricular and supraoptic nuclei ran through the ventral hypothalamus, but terminated in (i) the external layer of the rostral ME, and (ii) in the posterior lobe of the hypophysis.

Animals↗

PubMed1985

Immunocytochemical demonstration of neuropeptides and serotonin in the tapeworm Diphyllobothrium dendriticum.

The present immunocytochemical study concerns the distribution of four neuropeptides, FMRF-amide, vasotocin, leu-enkephalin and neurotensin, and of the bioamine serotonin in the plerocercoid larva of Diphyllobothrium dendriticum. Anti-FMRF-amide and vasotocin-reactivity occurs in perikarya and nerve fibres in the CNS and PNS of this worm. The peptide-containing fibres surround and seem to innervate the musculature and to terminate beneath the basal lamina of the tegument at the inner surface of the bothridia, suggesting a neurotransmitter function. Anti-leu-enkephalin reaction occurs in perikarya and fibres in the main nerve cords and in the PNS. Anti-neurotensin reactive fibres were observed in the neuropile of the nerve cords. Serotonin immunoreactivity was found in neurons in the ganglionic commissure of the brain and along the main nerve cords. This study is the first immunocytochemical identification of neuropeptides and serotonin in a parasitic flatworm and the information gained may be of importance for the development of new antihelminthics.

Animals↗

PubMed1996

Blood vessel adaptation to gravity in a semi-arboreal snake.

The effects of vasoactive agonists on systemic blood vessels were examined with respect to anatomical location and gravity acclimation in the semi-arboreal snake, Elaphe Obsoleta. Major blood vessels were reactive to putative neurotransmitters, hormones or local factors in vessel specific patterns. Catecholamines, adenosine triphosphate, histamine and high potassium (80 mM) stimulated significantly greater tension per unit vessel mass in posterior than anterior arteries. Anterior vessels were significantly more sensitive to catecholamines than midbody and posterior vessels. Angiotensin II stimulated significantly greater tension in carotid artery than in midbody and posterior dorsal aorta. Arginine vasotocin strongly contracted the left and right aortic arches and anterior dorsal aorta. Veins were strongly contracted by catecholamines, high potassium and angiotensin II, but less so by adenosine triphosphate, arginine vasotocin and histamine. Precontracted vessel were relaxed by acetylcholine and sodium nitroprusside, but not by atrial natriuretic peptide or bradykinin. Chronic exposure of snakes to intermittent hypergravity stress ( + 1.5 Gz at tail) did not affect the majority of vessel responses. These data demonstrate that in vitro tension correlates with that catecholamines, as well as other agonists, are important in mediating vascular responses to gravitational stresses in snakes.

Adaptation, Physiological↗

PubMed1995

Effects of water restriction during growth and adulthood on renal function of bobwhite quail, Colinus virginianus.

Renal function and osmoregulation were studied in bobwhite quail (Colinus virginianus) raised with unrestricted water (chronically unrestricted group) or restricted water (chronically restricted group). There was no difference in urine concentrating ability between adult and juvenile (3.5 or 7.5 week-old) quail. A filtration marker (polyethylene glycol) was infused into adult quail via osmotic minipumps and responses to the following regimens studied: ad libitum water intake, short-term (4-day) water restriction, and acute (1-day) dehydration (withdrawal of all drinking water). Chronically restricted quail had higher urine-to-plasma ratios of polyethylene glycol and lower urine flow rates during short-term restriction. A greater proportion of the reduction in urine flow rate during dehydration was attributable to enhanced tubular reabsorption, rather than reduced rates of filtration, in chronically restricted than in chronically unrestricted birds. Chronically restricted birds also had higher maximum urine-to-plasma ratios of polyethylene glycol (but not higher urine osmolality). These differences occurred in the face of arginine vasotocin concentrations that were not different in the two groups of birds (approximately 15 pg.ml-1 during hydration, and 45 pg.ml-1 during water restriction or dehydration). These observations suggest that chronically restricted quail have an enhanced responsiveness of tubular reabsorption to dehydration, a finding consistent with previous observations of tubule hypertrophy and hyperplasia in these birds (Goldstein and Ellis 1991). Despite this, no difference was found in medullary cAMP levels, either basal or arginine vasotocin- or forskolin-stimulated, in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1982

Immunoreactive neuropeptide systems in avian embryos (domestic mallard, domestic fowl, Japanese quail).

In embryos of the domestic mallard, domestic fowl, and Japanese quail vasotocin-, mesotocin-, luliberin (LHRH)-, met-enkephalin-, corticotropin-, and somatostatin-immunoreactive perikarya and fiber formations were visualized at different incubation stages by means of the PAP technique (Sternberger 1979). The most striking results were: (1) Vasotocin-, mesotocin-, and luliberin-immunoreactive systems display, up to the late embryonic period, morphological features most probably related to a neurohormonal function. (2) Met-enkephalin immunoreactivity appears very late during embryonic life; it is restricted to fiber networks and not found in perikarya. (3) Corticotropin immunoreactivity is observed in the tuberal region temporarily at the end of the second and the beginning of the last third of the incubation period. (4) Somatostatin-immunoreactive material is present (i) at the end of the first third of incubation, in association with the olfactory system; (ii) during the same period, adjacent to thin-layered portions of the roof of the brain; (iii) shortly thereafter, in cells of both pancreatic primordia and thyroid gland; and (iv) onward from the middle of the incubation period, in a mesencephalic cell group. The striking difference, in the early embryo, between the mature somatostatin plays a role in the development of the brain, as well as the pancreas, and the thyroid gland.

Adrenocorticotropic Hormone↗

PubMed1991

Antidiuretic-hormone-induced morphological changes in the ampullary epithelium of the frog semicircular canal.

Morphological changes induced by in vitro treatment with arginine-vasotocin, the frog antidiuretic hormone, were studied in the ampullary epithelium of the frog semicircular canal. Morphological changes appeared only in the apical side of the dark cells, while the basal part of these cells and the other cells lining the semicircular canal did not show any change. Changes consisted of the appearance of numerous small vesicles in the apical cytoplasm and the development of microvilli on the apical plasma membrane of the dark cells. These results suggest that arginine-vasotocin could play a role in the regulation of endolymph section.

Animals↗

PubMed1987

Hormonal facilitation in the release of sperm from the spermatheca of the red-spotted newt.

Several neurotransmitters and hormones with potential to trigger a simultaneous contraction of the oviducts and the spermathecal myoepithelium were examined. Saline (0.05 ml), or 0.05 ml saline plus acetylcholine (9 mg), norepinephrine (50 micrograms), arginine-vasotocin (25 units), prostaglandin F2 alpha (3 micrograms) were injected into the spermathecal region of female newts (n = 24 per group). The numbers of sperm present in the cloacae of prostaglandin-injected animals (107 +/- 30 SEM) were significantly greater than the numbers detected in saline (27 +/- 5 SEM) and in uninjected (14 +/- 3 SEM) controls. Smaller and less consistent increases in the numbers of sperm were detected in the vasotocin- and norepinephrine-injected groups. Study of sections from ovulating female newts failed to produce evidence that pressure from the passage of ova through the posterior portion of the oviduct forced sperm from the spermatheca. Observations indicate an active role for the spermathecal myoepithelium in the discharge of stored sperm and of a role for prostaglandin F2 alpha in triggering that discharge.

Acetylcholine↗

PubMed1977

Modification of effects of biologically active peptides, caused by enzyme treatment, on the excitability of identifiable giant neurones of an African giant snail (Achatina fulica Férussac).

Physalaemin, which excites an identifiable mooluscan giant neurone (the TAN, tonically autoactive neurone), lost the effect after the trypsin treatment. Unexpectedly, this peptide shows an inhibitory effect on the same neurone after chymotrypsin treatment. Deamino-dicarba-(d-d-)oxytocin and d-d-Arg-vasotocin, which excite another identifiable neurone (the PON, periodically oscillating neurone) continue to show the effect after chymotrypsin treatment (6 h). But d-d-Arg-vasotocin losts the effect on the PON after trypsin treatment.

Amino Acid Sequence↗

PubMed2006

Absence of oxytocin in the central nervous system of the snake Bothrops jararaca.

We used four complementary techniques to investigate the presence of oxytocin peptide in the hypophysis and brain of the snake Bothrops jararaca. A high-pressure liquid chromatographic analysis failed to show oxytocin in extracts of hypophysial and brain tissues but provided estimative values of the amounts of vasotocin (12 ng/mg hypophysis and 0.5 ng/mg brain) and mesotocin (500 pg/mg hypophysis and 8 pg/mg brain). Western blots with a polyclonal anti-oxytocin antibody failed to detect oxytocin in both tissues but detected compounds with higher molecular weight than oxytocin, as well as a relatively weak cross-reactivity with mesotocin. The reverse transcription-polymerase chain reaction analysis failed to detect the expression of oxytocin gene transcript, but detected a transcript related to the mesotocin-neurophysin precursor in both tissues. Immunohistochemistry with the same anti-oxytocin antibody detected strong staining in the neurohypophysis and in few fibers in the inner zone of the median eminence, which was not abolished by pre-adsorption of this antibody with oxytocin, vasopressin, vasotocin or mesotocin and might not be attributed to oxytocin. In conclusion, our data demonstrate the absence of oxytocin in the central nervous system of the snake B. jararaca and underline the pitfalls that can result from the use of a single technique to investigate the presence of peptides in tissues.

Animals↗

PubMed2003

Distribution of a novel avian gonadotropin-inhibitory hormone in the quail brain.

We recently identified a novel hypothalamic neuropeptide inhibiting gonadotropin release in the quail brain and termed it gonadotropin inhibitory hormone (GnIH). In this study, we investigated the localization and distribution of GnIH in both sexes of adult quails by immunohistochemistry with a specific antiserum against GnIH and in situ hybridization. Quantitative analysis demonstrated that the concentration of GnIH in the diencephalon was greater than that in the mesencephalon without sex difference. GnIH concentrations in the cerebrum and cerebellum were below the level of detectability. Clusters of GnIH-like immunoreactive (GnlH-ir) cell bodies were localized in the paraventricular nucleus (PVN) of the hypothalamus. There was no significant difference in the number of GnlH-ir cells in the PVN between males and females. By double immunostaining with antisera reacting with GnIH or avian posterior pituitary hormones (vasotocin and mesotocin), GnIH-ir cells were found to be parvocellular neurons in the ventral portion of PVN, which showed no immunoreaction with the antisera against vasotocin and mesotocin. In situ hybridization revealed the cellular localization of GnIH mRNA in the PVN. GnIH-ir nerve fibers were however widely distributed in the diencephalic and mesencephalic regions. Dense networks of immunoreactive fibers were found in the ventral paleostriatum, septal area, preoptic area, hypothalamus, and optic tectum. The most prominent fibers were seen in the median eminence of the hypothalamus and the dorsal motor nucleus of the vagus in the medulla oblongata. Thus, GnIH may participate not only in neuroendocrine functions, but also in behavioral and autonomic mechanisms.

Animals↗

PubMed1996

Angiotensin II-binding sites in chicken brain and pituitary: autoradiographic localization.

The distribution of binding sites for 125I-Val5-angiotensin II in the brain and the pituitary of control and dehydrated adult chickens of both sexes was determined by receptor autoradiography. Specific 125I-Val5-angiotensin II binding was mainly located in sensory areas, the limbic system and the hypothalamus including circumventricular organs and the nucleus paraventricularis. Since both the central angiotensin II system and the avian antidiuretic arginine-vasotocin system interact in osmoregulation, possible changes in angiotensin II binding intensities after dehydration were investigated in hypothalamic areas known to be involved in body-fluid homeostasis. There was an obvious increase in binding sites neither in areas where arginine-vasotocin synthesizing neurons were located, e.g. the nucleus paraventricularis and nucleus supraopticus, nor in other relevant areas for osmoregulation, e.g. the circumventricular organs of the hypothalamus. Furthermore, no sex difference in angiotensin II binding was observed.

Angiotensin II↗

PubMed1983

Bulk flow of amniotic fluid water in response to maternal osmotic challenge.

Amniotic fluid volume is regulated by a complex system of fluid exchanges with fetal and maternal fluid compartments. To assess possible hormonal control of amniotic fluid water exchange with the maternal vascular compartment, we studied the effect of intra-amniotic injections of prolactin, vasopressin, or vasotocin on the amniotic to maternal water flux induced by the acute intravenous infusion of mannitol to the pregnant ewe. This mannitol stimulus increased amniotic fluid osmolality secondary to a shift of free water to the maternal vascular/extracellular compartments. Prior intra-amniotic injection of prolactin but not vasopressin or vasotocin blunted the amniotic fluid osmolar response to maternal mannitol infusion. These results suggest that resorption of amniotic fluid water may occur at the chorioamnion and that amniotic fluid prolactin may have a regulatory function in amniotic fluid volume and osmolar homeostasis.

Amniotic Fluid↗

PubMed1996

Testosterone effects on vasotocinergic innervation of sexually dimorphic medial preoptic nucleus and lateral septum during aging in male quail.

Vasotocin fibers are known to innervate regions important in the regulation of sexual behavior and neuroendocrine systems in quail. In this experiment, vasotocinergic innervation of the lateral septum and of the sexually dimorphic medial preoptic nucleus was studied during reproductive aging relative to sexual behavior or following testosterone (T). There were 4 groups of male Japanese quail (Coturnix japonica) studied: adult reproductive (6 month, n = 4), photoregressed adult (n = 5), old senescent (36 month, n = 4), and old testosterone-treated (n = 5). Immunocytochemistry for vasotocin (VT) was performed on serial sections and quantification of the density of VT-positive fibers was performed by image analysis. Results showed a highly significant decrease in VT-immunocytochemical staining in photoregressed and in old senescent males; whereas T-treatment in old males was associated with recovery of VT-immunocyto-chemical staining, comparable to the adult reproductive male. Previous experiments have shown that T treatment restimulates sexual behavior in senescent males similar to the recovery of sexual behavior in T-treated castrates. These results indicate that the VT system may be associated with the behavioral recovery observed in senescent T-treated males.

Aging↗

PubMed1985

Reduction of vagal pressor reflexes by neurohypophyseal peptides and related compounds.

The effects of intracisternal injections of [Lys8]vasopressin and [Arg8]vasopressin (25, 50, 100, 200 mU/kg) and related compounds oxytocin (25, 50, 100, 200 mU/kg), felypressin (25, 50, 100, 200 mU/kg) and vasotocin (100, 200, 400, 800 ng/kg) on the acute neurogenic pressor responses to afferent vagal stimulation (5, 10, 20 and 30 Hz) were studied in urethane-anaesthetized dogs. [Arg8]vasopressin and [Lys8]vasopressin (50, 100, 200 mU/kg) elicited a significant decrease in the pressor responses. The depressor effects of oxytocin (50, 100, 200 mU/kg) were less marked and felypressin or vasotocin remained inactive. These results suggest that vasopressin, and oxytocin, containing neurons may be modulators involved in central cardiovascular regulation. Since these cardiovascular reflexes are related to an increase in sympathetic tone, the present work suggests that neurohypophyseal peptides could play an inhibitory role in the regulation of blood pressure through a central inhibition of sympathetic tone. In term of structure-activity relationships the present work suggests that under our experimental conditions the sequence 1-5 of amino acids in vasopressin is important for the depressor action.

Animals↗