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Abstracts from VI International Symposium on Avian EndocrinologyMarch 31 - April 5, 1996 Chateau Lake Louise, Alberta Continued in vitro Model to Study Pools for Thyroid Hormones in the Brain of Chickens: Cultured AstrocytesB. Gereben, T. Bartha, P. Gálfi, P. Rudas University of Veterinary Science, Department of Physiology and
Biochemistry, Budapest H-1400, P.O. Box 2, Hungary In vivo data suggest the existence of different kinetic pools for thyroid hormones in the brain of chicken. In order to be able to answer questions with respect to the role of certain cell-types in this phenomenon, we have established cultures of astrocytes from the telencephalon of the chicken embryo. On the basis of novel data of other groups, suggesting the active role of the cytoskeleton in hormone action, we have paid special attention to intermediate filaments during characterisation of the cultures. Vimentin epitopes were studied by two monoclonal antibodies (clones Vim3B4 and V9) in matured GFAP+ astrocytes, using double-immunofluorescence. Intensive Vim3B4 staining was detected in cell bodies but not in numerous cell-processes. The V9+ epitope was absent in the astrocyte cultures. Culture dynamics were also followed by measurement of the total protein content. A kinetic pilot study using 125I-T3 and 125I-T4 indicated that intracellular hormone uptake was increased after hypothyroid incubation. Investigations are planned to reveal questions with respect to deiodination processes, thyroid kinetics and thyroid hormone dependence of the cytoskeleton. Changes in Spontaneous Feeding Activity and Prolactin-Induced Hyperphagia Following Lesions of the Ventromedial Hypothalamus in Ring DovesJ.D. Buntin, R M. Hnasko, P.H. Zuzick Department of Biological Science, University of
Wisconsin-Milwaukee, Milwaukee, WI 53201, USA Prolactin (PRL) stimulates feeding activity and body weight gain in ring doves when injected systemically or intracranially, and the ventromedial nucleus of the hypothalamus (VMN) is more effective than 6 other PRL-sensitive brain sites in promoting these changes. To further clarify VMN involvement in feeding behavior, we examined the effects of VMN destruction on spontaneous feeding and the hyperphagia induced by intracerebroventricular (ICV) injections of PRL. Male doves were fitted with chronic infusion cannulae targeted for the lateral cerebral ventricle. At the same time, birds received bilateral radiofrequency lesions aimed at the VMN (lesion group) or had electrodes lowered to the VMN without passage of current (control group). Food intake and body weight were monitored daily during the post-operative period. When food intake had returned to baseline levels, each bird received ICV injections of 1 µg ovine PRL once daily for 5 days. Data analysis was restricted to lesioned birds sustaining damage to > 50% of both VMN with minimal damage to adjacent structures (n=6) and to control birds with electrode tracts visible in the VMN (n=6). During the post-operative period, lesioned birds exhibited a transient increase in food intake and a sustained increase in body weight. Elevations in food intake and body weight on days 5-9 were two-fold higher in lesioned birds (35% and 14%, respectively) than in controls (P<.01). In contrast to these effects, lesioned birds and controls exhibited similar elevations in food intake and body weight during the PRL treatment period. We conclude that VMN destruction strongly perturbs feeding and body weight regulation in doves. Nevertheless, the VMN is not essential for the expression of PRL-induced hyperphagia even though it is an effective site of PRL action in this regard. (Supported by NIMH grant MH 41447) Localization of Galanin and its Receptors in the Avian BrainY. Azumaya, K. Tsutsui Faculty of Integrated Arts and Sciences, Hiroshima University,
Higashi-Hiroshima 739, Japan Recently, we isolated a C-terminally amidated 29-residue peptide from the quail oviduct. This peptide was identified as avian galanin. Galanin is known to be a multifunctional peptide in the neuroendocrine system in mammals, while little information is available for galanin action in the central nervous system in birds. In the present study, therefore, we examined the presence and the localization of galanin and its receptors in the quail brain. The binding of [125I]-avian galanin to brain tissues was specifically inhibited as a function of the concentrations of unlabelled avian galanin. Scatchard plot analysis of galanin binding revealed a Kd of 0.281 nM, suggesting the presence of a single class of high affinity binding site. The number of galanin-binding sites (when compared on unit weight basis) was maximal in the interbrain, including the preoptic and hypothalamic regions, and minimal in the cerebellum. Galanin-like immunoreactivity was found in several discrete regions but the most intense immunoreaction was present in the diencephalon. Abundant immunoreactive cell bodies and/or fibers were localized in several preoptic and hypothalamic nuclei, i.e., the nucleus preopticus medialis (POM), the nucleus paraventricularis (PVN), the nucleus periventricularis hypothalami (PHN) and the nucleus infundibuli (IN). These nuclei are known to be involved with the control of male reproductive behavior and pituitary hormone secretion. These results therefore suggest that avian galanin may also act to modulate some reproductive behaviors and/or pituitary hormone secretion. Sexual Dimorphism in the Expression of Arg-Vasotocin in the Chicken BrainS.W. Barth, a. Jurkevich, R. Grossmann Institute for Small Animal Research, Department of Physiology,
Dörnbergstra_e 25-27, D-29223 Celle In avian species arginine vasotocin (AVT) plays an important role in the regulation of reproduction, particularly in reproductive behavior. Reflecting this, AVT immunoreactivity is sexually dimorphic in the preoptic area and in the bed nucleus of the stria terminalis (NST) of different avian species (e.g. Quail, Canary). It is, however, unknown which brain nuclei exhibit sexually dimorphic AVT expression in the chicken brain. We have therefore used in situ hybridization (ISH) and immunocytochemistry (ICC) to analyze AVT gene expressing neurons in the NST of adult male and female chickens. Northern blot hybridization was also used to quantify the AVT mRNA content in whole brains of hens and cockerels. In males AVT peptide containing neurons were detected in the NST and high concentrations of AVTIR were visible in projections from NST to the lateral septal area, whereas no AVTIR neurons were detected in the corresponding regions of the hen. These results correspond very well with ISH results: neurons containing AVT transcripts were labelled in the NST of males, but no specific hybridization signals were observed above neurons in the female NST. In addition, quantification by northern hybridization clearly demonstrated a significantly higher (P<0.005) AVT mRNA content in the male brain compared to females. Furthermore, in hens AVT gene expression in neurons of the NST was not upregulated after osmotic stimulation (water deprivation for 48 h) or at the time of oviposition. These results demonstrate, for the first time, that the AVT gene is expressed in the NST of chickens and exhibits a strong sexual dimorphism which is independent of physiological (osmotic stress or oviposition) stimuli. (Supported by the Deutsche Forschungsgemeinschaft) Effects of vip and grf on cyclic amp production IN THE Chicken Pituitary GlandN. Kansaku, K. Shimada, N. Saito Laboratory of Animal Physiology, School of Agricultural
Sciences, Nagoya University, Chikusa, Nagoya, Japan, 464-01 This study was designed to investigate the effects of VIP and GRF on cAMP production in the pituitary gland of chicken. The cephalic and caudal lobes were enzymatically dispersed with collagenase at 37°C. Dispersed cells were maintained for 72 h with M199 in the CO2 incubator. Following the incubation period, cells of the cephalic and caudal lobe were exposed to VIP and GRF, respectively. After the incubation, samples were centrifuged, the medium was harvested and stored at -20°C until RIA. The resultant cell pellet was stored at -80°C for cAMP determination. Secretion of PRL from the dispersed cells of cephalic lobe was significantly increased by VIP stimulation. VIP induced 4-fold increase of intracellular cAMP levels. Secretion of GH from the dispersed cells of caudal lobe was significantly increased by GRF stimulation. GRF also induced 2.5-fold increase of intracellular cAMP levels. The results of this study indicate that regionalized gene expression and hormone synthesis of PRL and GH, at least in part, depend on regionalized effects of VIP and GRF, respectively, and that gene expression of PRL and GH are mediated by intracellular cAMP. Distribution and Time Course of Immunoreactive FOS-like Protein Expression Within the Basal Forebrain of Cockerels Following DehydrationA. Jurkevich1, R. Grossmann Institute for Small Animal Research (FAL), Dömbergstr. 25-27,
D-29223 Celle, Germany; 1Institute of Ecology, Akademijos 2,
LT-2600 Vilnius, Lithuania Osmotic stress induced by dehydration results in a number of behavioral and endocrine responses and can modify gene transcription in neuronal circuits involved in these responses. Since changes in gene transcription are preceded by expression of nuclear transcription factors, including the Fos protein, their appearance in neurones may indicate cells activated by osmotic stimulation. The aim of this study was to determine the spatial and temporal patterns of immunoreactive (ir) Foslike protein expression in basal forebrain regions of cockerels during dehydration. The birds were deprived of water for 8, 18, 24, 30 or 48 h, respectively (n=3, for each time point). In normohydrated (control) cockerels most neurones were Foslike negative. During the first 30 h of dehydration, a gradual increase in the number of Foslike ir cells was observed in the ventromedial preoptic area, supraoptic, paraventricular and septal regions, dorsolateral and dorsomedial thalamus and along the nucleus of pallial commissure (nCPa). The number of Foslike ir cells in the nCPa positively correlated with changes in plasma osmolality, sodium and vasotocin (VT) concentrations during dehydration. Immunocytochemical double labelling revealed colocalization of Foslike and VT-ir predominatingly in parvocellular neurones in the supraoptic and paraventricular regions, starting from 30 h of osmotic stimulation. These findings demonstrate that many areas of the forebrain known to be involved in osmoregulation are progressively activated during dehydration. It is suggested that the VT neurosecretory system contains cellular groups which are differently activated by osmotic stress. (Supported by the DAAD and Deutsche Forschungsgemeinschaft) Effects of Active Immunization Against cVIP on Incubation Behaviour, Egg Production and Endocrinological Parametersin Turkey HensC. Morvan, M. Garreau-Mills, D. Guémené Station de Recherches Avicoles, INRA, Centre de Tours, 37380
Nouzilly, France Conflicting results have been reported about the effects of active immunization against VIP in domestic birds (El Halawani et al., 1993, Sharp et al., 1993). In turkeys, active immunization with chicken VIP depressed circulating prolactin, inhibited incubation expression and resulted in an increase in egg production. On the other hand, active immunization of bantam hens with cVIP before photostimulation prevented resumption of egg laying after transfer back to long photoperiods. The present study was therefore undertaken to further investigate the effects of active immunization against cVIP in turkeys. Medium White turkey hens, which had already shown incubation behaviour during a first productive period, were divided into two experimental groups (n=2x12): controls and turkeys actively immunized with synthetic cVIP-KLH conjugate. Each hen received four injections at 5-10 weeks intervals (50 µg cVIP per hen), starting ten weeks before photostimulation. Specific cVIP antibodies were detected in all immunized turkey hens during the experimental period. Although the immunization delayed the expression of incubation behavior, it failed to fully prevent its occurrence. As a consequence, comparable overall percentage of hens (33%) did express it under each treatment and comparable egg production was observed. Active immunization against cVIP resulted in significantly lower (P < 0.05) plasma prolactin levels in non broody immunized hens compared to non broody control hens. Plasma prolactin levels were higher in broody treated turkey hens compared to the controls, however, the differences were not significant (P>0.05). Plasma luteinizing hormone levels were comparable in both groups throughout the experimental period. As a conclusion, it appears that under our experimental procedure, active immunization against cVIP did not prevent incubation expression, or induce an increase in egg production while it induced divergent effects on plasma prolactin levels. The Stress Response and Autumn Dispersal in Willow TitsB. Silverin Department of Zoology, University of Göteborg, Medicinargatau
18, S-413 90 Göteborg, Sweden Willow tits (Parus montanus) defend a year around territory. During the autumn/winter period willow tits form a territorial flock consisting of the adult pair that previously bred in the area and 2-3 non-kin juveniles. For several reasons it is crucial for the juvenile to become a flock member, even at the cost of being a subdominant individual with a lower winter survival compared to dominant flock members. An experimental elevation of plasma levels of corticosterone during the dynamic period of flock establishment (July-August) makes juvenile willow tits disappear from the forest, or turn them into floaters. Adults, on the other hand, do not leave their territories as a result of a similar corticosterone treatment. Repeating the experiment in October, a time when permanent winter flocks have become established, did not induce a dispersal behaviour in juveniles, but they stayed on their territories. Adults showed the same response as in late summer, i.e. increasing plasma levels of corticosterone did not induce a dispersal behaviour but adults remained on their territories. As flock membership is crucial for the winter survival of juvenile willow tits, selection should work against any factor redirecting behaviour away from flocking. As field experiments showed that high corticosterone levels initiate a dispersal behaviour in juvenile willow tits during the flock establishment period, they should have a low sensitivity to environmental stressors during this period. A study on the response to capture stress in adult and juvenile willow tits showed that neither age group showed a marked response to handling stress in July. In September juveniles still showed a weak stress response. Adults, on the other hand, had become very sensitive to capture stress indicated by a rapid increase in their corticosterone levels after capture. In January both juveniles and adults responded rapidly and strongly to handling stress. Corticosterone and Behavioral Responses to Unpredictable EventsJ.C. Wingfield Department of Zoology, Box 351800, University of Washington,
Seattle, WA 98195, USA Mechanisms by which birds adjust their morphology, physiology and behavior to predictable changes in the environment (e.g. seasons, day/night) have been investigated for many decades. However, in recent years the behavioral responses to unpredictable events (e.g. inclement weather, habitat disturbance) have also received considerable attention. Facultative behavioral responses to, for example, severe weather include reduced reproductive and territorial behavior, enhanced foraging, increased locomotor activity associated with irruptive migration, and reduced metabolic rate at night. Considerable evidence now implicates a major role for corticosterone in these responses. Field evidence shows that plasma levels of corticosterone are elevated in birds during these facultative behavioral responses. Investigations in the field have also shown that many species have the ability to modulate their adrenocortical responses to unpredictable events either suppression or enhancement. There appear to be two major components to this modulation. One is seasonal, and found at the population level. The other is at the individual level and appears to be related to body condition. Role of Archistriatal Nucleus Taeniae in the Sexual Behavior of the Male Japanese QuailE. Adkins-Regan, R. Thompson, J. Goodson 218 Uris Hall, Cornell University, Ithaca, NY 14853-7601, USA Archistriatal nucleus taeniae (Tn) is the only telencephalic structure that concentrates sex steroids in non-oscine birds. It is believed to be the homolog of the centromedial portion of the mammalian amygdala, an area with a substantial chemosensory input known to be importantly involved in sexual behavior in rodents. The sexual function of Tn in birds, which rely less on chemosensory stimuli, is unknown. In this experiment, male Japanese quail housed on short days and implanted with testosterone propionate were given bilateral electrolytic lesions aimed at Tn or sham surgery. They were tested for a range of both appetitive and consummatory components of reproductive behavior, including the ability to develop a conditioned sexual response. Birds with successful bilateral lesions were slower to approach females and less likely to resume copulation after an ejaculation. They showed the same number of foam gland muscle movements to female and male stimuli, whereas controls showed more movements to female stimuli. These effects were not seen in birds with lesions outside of Tn. There were no deficits following Tn lesions in strutting or in the ability to execute the copulatory pattern, nor was there an impairment in the ability to develop the conditioned response. The pattern of effects of the lesions suggests that the primary deficit was in sexual arousal and interest in females. Electrolytic Lesions of Aromatase-Immunoreactive Neurons Disrupt Appetitive and Consummatory Aspects of Male Sexual Behavior in QuailJ. Balthazart, C. Castagna, P. Absil, M. Gérard, and D. Appeltants Laboratory of Biochemistry, University of Ličge, 17 place
Delcour, B-4020 Ličge, Belgium In male Japanese quail, appetitive sexual behavior can be measured by the time spend in front of, and looking through, a small window that provides a view of a female that will subsequently be released into the cage and allowed to copulate. This learned social proximity response develops only in birds exposed to sufficient levels of testosterone (T). Aromatization of T is required to activate both appetitive and consummatory aspects of sexual behavior, as shown by the fact that injections of the aromatase inhibitor, R76713 suppress all behavioral effects of T implants. Three groups of aromataseimmunoreactive (AROir) neurons are present in the quail preoptic area/anterior hypothalamus at the level of the medial preoptic nucleus (POM), paleostriatum ventralenucleus accumbens (PVTAc) and bed nucleus striae terminalis (BNST). In order to determine whether the same groups of AROir cells support both aspects of male sexual behavior, electrolytic lesions were placed at these 3 locations in birds bearing subcutaneous Silastic T implants that had learned the social proximity response. Lesions of POM and BNST almost completely abolished copulatory behavior and decreased but did not suppress the appetitive response. Lesions of the PVTAc were behaviorally ineffective. Taken together, these data demonstrate that similar endocrine mechanisms control the activation of both aspects of male sexual behavior but the neural sites mediating these effects may be partly different. Photoperiodic Regulation of Seasonal Changes in the Volume of Song-Control Nuclei in European StarlingsG.F. Ball, D.B. Bernard Department of Psychology; Johns Hopkins University, Baltimore,
MD 21218, USA Birdsong are vocalizations controlled by a specialized neural circuit commonly called the song control system. Brain nuclei in this circuit are larger in birds in breeding than in nonbreeding conditions. Elevated circulating testosterone (T) levels appear to mediate these changes, although photoperiod may have Tindependent effects. In the laboratory, animals housed on long, springlike photoperiods have elevated T and larger nuclei than birds on short, falllike days. In European starlings (Sturnus vulgaris) one song nucleus, the High Vocal Center (HVC) was larger in male starlings in reproductive condition (i.e., photosensitive) on an 11L:13D photoperiod than in males in nonreproductive condition (i.e., photorefractory) on 16L:8D. Additional experiments revealed that exogenous T treatment increased HVC volume in photosensitive but not photorefractory male and female starlings. In related studies (in collaboration with Dr. Fred Wilson at Kansas State University), intact or castrated male American tree sparrows (Spizella arborea) were maintained on short photoperiods or moved to long photoperiods for three weeks. Males exposed to long days had larger nuclei than males maintained on short days. This was true for both intact and castrated animals, but intact birds on long days had the largest nuclei of all of the groups. Similar studies on castrated and intact starlings failed to detect such testis independent effects. In summary, these results indicate that T increases song nucleus volumes, but these effects are modulated by photoperiodic condition. In some cases photoperiod can induce changes in song nucleus volume independently of the testes. cGnRH-I and Neuropeptide Systems Reflect Endocrine and Behavioral Changes during Reproductive AgingM.a. Ottinger, N. Thompson, Y. Fan, G.C. Panzica1, C. Viglietti-Panzica1, Q. Li Department of Poultry Sciences, University of Maryland,
College Park, MD, USA; 1University of Torino, Torino, Italy There is an age-related decline in reproduction in the male Japanese quail, which first appears as a decreasing incidence of sexual behavior, coincident with reduced fertility. This is followed by increasing evidence of endocrine failure at the level of the hypothalamus, as well as in testicular morphology and function, and finally reproductive failure or senescence. Sexual behavior has proven to be an excellent predictive index of the reproductive status of an individual, which has allowed us to categorize males according to chronological age and reproductive status, based on sexual behavior. The focus of this paper is hypothalamic function, particularly alterations in the cGnRH-I system during aging. We observed decreased cGnRH-I content in the preoptic and median eminence (ME) areas and attenuated amplitude of cGnRH-I release from hypothalamic slices in vitro. Studies on the immunohistochemical localization of ME vasotocin has shown that these peptides decrease dramatically in old senescent males and restored by exogenous testosterone implants. Other studies have shown that the opioid peptides inhibit cGnRH-I release from hypothalamic slices in vitro. Using double labelling, we are following the morphological localization of cGnRH-I and enkephalin relative to age to determine if the physical relationship of these systems changes during aging and relative to sexual behavior. (Research supported in part by NRICGP-USDA #92-37203-7742 (MAO) and NATO grant GCP, MAO) Luteinizing Hormone (LH), Gonadal Steroids and Prolactin in Relation to Social Behaviour in Male and Female Black-Headed Gulls during the Breeding PeriodA. Jurkevich, D. Maleckiene, M. Zurba, P.J. Sharp1 Institute of Ecology, Akademijos 2, Vilnius 2600, Lithuania;
1Roslin Institute, Roslin, Midlothian EH25 9PS UK The aim of this study was to determine the temporal interrelations between plasma levels of LH, prolactin (PRL), progesterone and gonadal steroids (T and E2) in male and female blackheaded gulls (Larus ridibundus) in relation to behavioral events during the breeding season. Blood sampling and behavioral observations were performed at the following stages of the breeding cycle: beginning of egglaying (one egg in a nest), incubation of a full clutch, hatching of young, rearing of young and fledging. In males, concentrations of LH and T were maximal at the onset of egglaying and declined during incubation and the rearing of young. Plasma LH increased when the young were fledging. In females, high levels of plasma E2 were associated with the onset of egglaying and rapidly decreased when the last egg in a clutch was laid, whereas LH concentrations did not change significantly throughout the period of study. At the onset of egglaying and incubation, the female/male ratios of T were 1:2.1 and 1:1.3, respectively, consistent with the role played by both mates in nest defence and maintenance of territoriality. During rearing and fledging, this ratio increased to 1:5. The concentration of T positively correlated with the intensity of intraspecific agonistic interactions. Progesterone levels in both sexes were maximal at the onset of incubation and then decreased, particularly in females. In both sexes, the concentration of plasma PRL rose to a maximal level at the end of incubation and then decreased twofold during the rearing of the young. These observations indicate that in the blackheaded gull, temporal relationships between hormones involved in the endocrine control of breeding and related behaviour differ from those reported for another singlebrooded altricial species. |