Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). "June 2006." Includes bibliographical references (leaves 67-75). Also available via the World Wide Web.

Orientador: Heitor Moreno Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-08T07:56:02Z (GMT). No. of bitstreams: 1 Martins_LuizClaudio_M.pdf: 906458 bytes, checksum: 5eca8eb707e90d3712220013fdc6e1f3 (MD5) Previous issue date: 2006 / Resumo: A vasopressina é um nonapeptídeo que possui moléculas de cisteína na posição um e seis ligadas por uma ponte dissulfeto, sendo sintetizada nos neurônios localizados nos núcleos supraópticos e paraventriculares do hipotálamo e transportada para a hipófise posterior onde é armazenada em forma de grânulos. A vasopressina tem seu efeito vasopressor conhecido deste o final do século XIX. Sua secreção é complexa, sendo liberada em situações de choque, hemorragias, síncope vagal, entre outras. Possui três tipos de receptores (V1, V2 e V3), sendo que o receptor V1 fica localizado nos vasos sanguíneos e é responsável pelo efeito vasoconstritor. Mais recentemente, o uso da vasopressina como medicação coadjuvante às catecolaminas no tratamento do choque vasodilatatório vem sendo descrito. A vasopressina normaliza a pressão arterial possibilitando que as doses de catecolaminas sejam diminuídas. É descrito que o uso da vasopressina em situações de choque é também associado a efeitos colaterais, como isquemia de mucosas, pele e miocárdica. O uso clínico rotineiro da vasopressina é muito limitado, sendo pouco conhecidas as doses que devem ser usadas para melhorar a hemodinâmica sem prejudicar a oferta tecidual de oxigênio. Neste estudo foi investigado os efeitos hemodinâmicos da vasopressina, em doses progressivas em cães anestesiados. Dezesseis cães sem raça definida, foram anestesiados e distribuídos aleatoriamente em dois grupos: Controle e Vasopressina. O grupo Vasopressina recebeu vasopressina nas doses 0,01 ; 0,1 e 1,0 U/kg/min por 10 minutos. Após a infusão foi realizado estudo hemodinâmico. Nas doses de 0,1 e 1,0 U/kg/min observou-se diminuição do índice cardíaco e da freqüência cardíaca, aumento da pressão arterial média e do índice de resistência vascular sistêmica. Na dose de 1,0 U/kg/min observou-se aumento do índice da resistência vascular pulmonar. Os resultados nos permitem concluir que a vasopressina pode ser útil nomanuseio do choque vasoplégico. Porém, a possibilidade de ocorrência de efeitos cronotrópicos e inotrópicos negativos podem deteriorar o estado metabólico no choque / Abstract: Introduction: Vasopressin is a neuropeptide with potent vasoconstrictor effect, but clinical experience with vasopressin in continuous infusion has been limited. In this study, we investigated the effects of vasopressin in continuous infusion on hemodynamic parameters in anesthetized dogs. Material and Methods: Mongrel dogs (n = 16) anesthetized and randomized in two groups: control and vasopressin. The vasopressin group received the following doses: 0.01 U/kg/min, 0.1 U/kg/min and 1.0 U/kg/min during 10 min. After infusion invasive hemodynamic study was performed. Results: Vasopressin continuous infusion in doses of 0.1 and 1.0 U/Kg/min for 10 minutes induced a significant decrease of heart rate and cardiac index, and significant increase of mean arterial pressure and systemic vascular resistance index. The 1.0 U/kg/min dose also induced a significant increase of pulmonary vascular resistance index. Conclusion: Increase of MAP and SVRI suggest vassopressin might be useful in managing a state of vasoplegic shock, however negative inotropic and chronotropic effects will also occur, what may deteriorate the metabolic state in a vasoplegic shock. Clinical experience utilizing vasopressin in vasoplegic shock is limited, as well as which dose should be used to minimize its deleterious effects / Mestrado / Mestre em Farmacologia

A homeostase hidro-eletrolítica é controlada por informações sobre volume e a concentração dos íons dos líquidos corporais. Alterações da osmolalidade são detectadas por receptores presentes em diversas regiões do SNC, entre as quais os órgãos circunventriculares. Alterações conformacionais nestas células ativam neurônios localizados nos núcleos paraventricular (PVN) e supra-óptico (SON) do hipotálamo, que secretam ocitocina (OT) e vasopressina (AVP). A osmolalidade plasmática aumenta em conseqüência da alimentação, o que induz a secreção de OT e AVP. Os esteróides ovarianos podem influenciar o balanço de líquidos, modulando sistemas hormonais que regulam tanto o consumo quanto a excreção de água, ou agindo diretamente em neurônios ocitocinérgicos e vasopressinérgicos do hipotálamo. No entanto, esta ação não é ainda entendida. É possível que esses sistemas respondam de forma diferente às variações de estrógeno, talvez por ação direta através de receptores de estrógeno tipo em neurônios OT e AVP do PVN e SON, e por ação indireta através de receptores de estrógeno tipo em órgãos circunventriculares. O objetivo do presente trabalho foi avaliar a participação do estradiol na modulação da secreção de AVP em resposta ao estímulo osmótico induzido pela realimentação após jejum. Para tanto, foi realizada a determinação da concentração plasmática de AVP, a análise da ativação de neurônios AVP, o conteúdo protéico de ER no PVN e no SON bem como a ativação neuronal pela expressão de FOS e a expressão de ER nos órgãos circunventriculares de animais ovariectomizados tratados com estradiol ou veículo. Os resultados mostram que a realimentação após jejum de 48 horas aumenta a expressão de FOS e a expressão da proteína de ER no PVN e SON, a expressão de FOS nos órgãos circunventriculares estudados e a concentração plasmática de AVP. No entanto, não foi observada diferença significativa entre os tratamentos. Houve uma inibição da expressão de ER nos órgãos circunventriculares estudados. Aparentemente, o estradiol não participa da elaboração de uma resposta frente ao estímulo osmótico induzido pela realimentação e não interfe na ativação de neurônios AVP e na secreção desse hormônio para circulação sanguínea. / The hydroelectrolyte homeostasis is controlled by information on volume and concentration of ions in the body fluids. Osmolality changes are detected by receptors in various regions of the CNS, including the circumventricular organs. Conformational changes of these cells activate neurons located in the paraventricular (PVN) and supraoptic (SON) nucleus of the hypothalamus, which secrete oxytocin (OT) and vasopressin (AVP). Feeding increases the plasma osmolality which induces the secretion of AVP and OT. Ovarian steroids may influence the balance of fluids modulating hormonal systems that regulate both consumption and excretion of water or acting directly on oxytocinergic and vasopressinergic neurons of the hypothalamus. However, this action is not clearly understood. It is possible that these systems respond differently to the estrogen changes perhaps by direct action through estrogen receptor type in AVP and OT neurons of the PVN and SON, and by indirect action through estrogen receptor type in circumventricular organs. The objective of this study was to evaluate the participation of estrogen in the modulation of AVP secretion in response to osmotic stimulus induced by refeeding after fasting. For this purpose, we performed the determination of plasma AVP, the analysis of the activation of AVP neurons, the protein content of ER in the PVN and SON as well as activation by neuronal expression of FOS and the expression of ER in the circumventricular organs in estrogen-primed and -unprimed ovariectomized animals. The results show that refeeding after fasting for 48 hours increases the expression of FOS and ER protein in the PVN and SON, the expression of FOS in the circumventricular organs studied and plasma AVP. However, there was no significant difference between treatments with estrogen or vehicle. There was an inhibition of ER expression in the circumventricular organs studied. Apparently, estrogen does not participate in the preparation of a response to the osmotic stimulus induced by refeeding and it does not interfere in the activation of AVP neurons or the secretion of this hormone to the bloodstream.

Oxytocin (OT) and vasopressin (AVP) are neuropeptides with diverse effects on social behavior, cognition and stress responses. Recent studies suggest that OT facilitates and responds to affiliative forms of human-animal interaction (HAI). However, previous studies measuring OT and AVP in dogs have been limited to measures from blood or urine, which present concerns related to the invasiveness of sample collection, the potential for matrix interference in immunoassays, and whether samples can be collected at precise time points to assess event-linked endocrine responses. Previous studies from our laboratory validated salivary measures of OT and AVP in dogs, however, it is currently unknown whether these measures respond dynamically to aspects of HAI. Here, we investigated the effects of affiliative forms of HAI on both plasma and salivary OT and AVP in dogs. We employed a within-and between-subjects design with a group of Labrador retrievers and Labrador retriever x golden retriever crosses (23 females, 15 males). Half of the dogs engaged in 10 min of free-form friendly interaction with a human experimenter (HAI condition), and the other half rested quietly in the same environment, without human interaction (control condition). We collected blood and saliva samples before, and immediately following both experimental conditions, and all samples were analyzed using enzyme-linked immunosorbent assays (ELISAs) following previously validated protocols. Dogs participating in HAI exhibited a significant increase in both salivary OT (+ 39%) and plasma OT (+ 5.7%) whereas dogs in the control group did not. Salivary AVP showed no change in the HAI group but increased significantly (+ 33%) in the control group. Plasma AVP decreased significantly following HAI (13%) but did not change across time in the control condition. Within the dogs exposed to HAI, increases in salivary OT, and decreases in plasma AVP, were predicted by the extent of affiliative behavior between the dog and human (indexed by scores from a principal components analysis of social behaviors between the dog and human). Collectively our results suggest that measures of salivary OT and AVP provide useful biomarkers in studies of HAI, and afford a flexible and non-invasive toolkit than can be employed in diverse research contexts.

Immunocytochemical studies have demonstrated that nerve fibers containing immunoreactive oxytocin and vasopressin project to many areas of the central nervous system, including the hippocampus and the lateral septum (Buijs, 1980; Sofroniew and Weindl, 1978). Biochemical, physiological and behavioral studies of the effects of these peptides on the CNS have indicated that they are involved in functions as diverse as the control of serotonin turnover (Auerbach and Lipton, 1982), the regulation of body temperature (Kasting et. al., 1979) and the retention of conditioned behavior (de Wied et. al., 1974; Koob and Bloom, 1982). The presence of immunoreactive vasopressin (iAVP) in the hippocampus of Wistar rats was confirmed by radioimmunoassay. The vasopressin content of the dorsal hippocampus was 30.3 ± 7.3 pg iAVP/mg soluble protein and that of the ventral hippocampus was 81.4 ± 8.3 pg iAVP/mg soluble protein, while tissue from the cerebral cortex contained no detectable vasopressin. That this immunoreactivity was due to vasopressin was confirmed by the absence of immunoreactivity in hippocampal or cortical tissue from Brattleboro rats, which are genetically unable to synthesize vasopressin. Vasopressin applied by iontophoresis was found to increase the activity of neurones in the lateral septum and in the hippocampus of the anesthetized rat. There was no obvious difference between the response of spontaneously active cells and the response of cells excited by continuous iontophoresis of glutamate or acetylcholine. Repeated application of vasopressin resulted in a decline in the magnitude of the response, but at least part of this decline was due to progressive blockage of the micropipette barrel rather than to tachyphylaxis. Oxytocin, tested only in the septum, was without effect. When applied by superfusion onto rat hippocampal slices, the NHP peptides were found to increase the activity of 88% of spontaneously active cells and to induce activity in many neurones that were not spontaneously active. Arginine vasopressin, lysine vasopressin, arginine vasotocin, and oxytocin were found to be of roughly equivalent potency, producing a dose dependent response in the range 10⁻⁹-10⁻⁶M. Most cells were tested with more than one peptide and were always found to respond either to all or to none of them. There was no decline in responsiveness when cells were subjected to repeated applications of peptide, but continuous application caused the cells to become unresponsive. Following continuous application of oxytocin, a cell failed to respond to both oxytocin and vasopressin, as would be expected if the two peptides were acting on the same receptor. The analogues ddOT, ddAVP, and Gly⁷0T were also active, but the oxytocin fragment PLG had no effect, and the vasopressin fragment DGAVP was extremely weak. The response to the peptides could be blocked by vasopressin antagonists. The peptide sensitive cells appeared to be pyramidal cells rather than interneurones, since the peptide induced activity could be inhibited for about 200-600 msec by electrical stimulation of the stratum radiatum. / Arts, Faculty of / Philosophy, Department of / Graduate

Vasopressin, a hormone released from the neurohypophysis, contributes to the regulation of body fluid balance through its known actions on the kidney and the vasculature. Release of vasopressin is influenced by plasma osmolality and by afferent activity from sensory receptors in the high and low pressure vascular systems. Previous studies have not defined the relative importance of the carotid sinus baroreceptors, aortic baroreceptors and atrial receptors in the control of the plasma concentration of vasopressin in the rabbit. Experiments were carried out in anaesthetized rabbits to define the quantitative relationship between stimulation of the carotid sinus baroreceptors and the plasma concentration of vasopressin. This relationship was examined in the presence and absence of afferent input from the aortic and atrial receptors. Changes in blood volume were induced to produce a change in the stimulus to the aortic baroreceptors and atrial receptors at high or low, constant carotid sinus pressure. Section, of the aortic depressor nerves and the vagus nerves allowed examination of the individual contributions of atrial receptors or aortic baroreceptors on the plasma concentration of vasopressin. It was also possible to examine the interaction between the carotid sinus baroreceptors and the aortic and atrial receptors. The results showed that plasma concentration of vasopressin was reduced by minimal stimulation of carotid sinus baroreceptors and that maximal inhibition of the release of vasopressin was achieved with a relatively low total arterial baroreceptor input. No influence of carotid sinus baroreceptors on vasopressin release was seen in the presence of intact aortic baroreceptors demonstrating the important interaction between the effects of stimulation of these two sets of receptors. It was not possible to demonstrate, in the rabbits used in this study, a significant contribution of atrial receptors to the control of vasopressin release either in response to changes in carotid sinus pressure or in response to changes in blood volume. To minimize the inhibitory effect of arterial baroreceptors on the release of vasopressin the aortic depressor nerves were cut and carotid sinus pressure was set at a low level. It was still not possible to demonstrate an effect of a reduction in blood volume on vasopressin release, confirming the absence of a contribution from atrial receptors in the anaesthetized rabbit. There appears to be considerable variation between species in the contribution of the different receptor groups to the release of vasopressin. The results suggest that in the normal rabbit there is likely to be significant tonic inhibition of the release of vasopressin by stimuli arising from arterial baroreceptors. The absence of a demonstrable influence of atrial receptors in these rabbits is consistent with findings in primates but differs from those in dogs. It is unlikely that changes in plasma vasopressin concentration induced by small changes in blood volume contribute to the control of arterial pressure through direct effects on vascular resistance and capacitance. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

The effect or indomethacin and its vehicle on blood pressure was studied in conscious rabbits during the infusion of three vasopressors. The cyclooxygenase inhibitor raised mean arterial pressure 12 (vehicle: 3) mm Hg during norepinephrine infusion, 5 (vehicle: 0) mm Hg during angioten- sin II infusion, and 5 (vehicle: −8) mm Hg during arginine vasopressin infusion. When saline was given in place of vasopressors, indomethacin failed to alter blood pressure. Since indomethacin elevated pressure in the presence, but not the absence, of all three vasopressors, the possibility that elevation of blood pressure per se stimulates synthesis of vasodilator prostaglandins was considered. A pressor action of indomethacin was observed in ganglion-blocked animals, in which absolute blood pressure remained below normotensive levels during angiotensin II infusion. Thus, indomethacin raised arterial pressure during the infusion of norepinephrine, angiotensin II, and vasopressin, and this action was not influenced by manipulation of blood pressure. These results suggest that each vasopressor promotes prostaglandin synthesis independently to a degree sufficient to restrain its pressor action.

Beacon is a 73-amino acid peptide encoded by a novel gene in the hypothalamus of Israeli sand rat Psammomys obesus. Reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemical techniques were used to investigate the presence of beacon mRNA and the distribution of beacon-immunoreactivity (irBC) in the hypothalamus of ICR mice. RT-PCR experiments revealed beacon mRNA in the mouse hypothalamus. Using a rabbit polyclonal antiserum directed against the synthetic C-terminal peptide fragment (47-73), irBC was detected in the mouse hypothalamus and pituitary. In the hypothalamus, irBC was concentrated in perikarya of the supraoptic (SO), paraventricular (PVH) and accessory neurosecretory nuclei and in cell processes of the median eminence and pituitary stalk. In the pituitary, irBC was noted mainly in the posterior lobe. Double-labeling the hypothalamic sections with guinea-pig vasopressin-antiserum or mouse monoclonal oxytocin-antibody and beacon-antiserum revealed that <30% of vasopressin-immunoreactive neurons and nearly all oxytocin-immunoreactive neurons in the PVH and SO were irBC. The result shows the presence of beacon mRNA in the mouse hypothalamus, and the distribution of irBC is distinctively different from that reported in the hypothalamus of Psammomys obesus, but similar to that of the Sprague-Dawley rats described in our earlier study. More interestingly, Blast search uncovered a 73-amino acid peptide, human ubiquitin-like 5, which has the same exact sequence as beacon. Thus, irBC observed in the mouse brain could be that of ubiquitin-like 5.

With the use of an antiserum against human apelin-36, apelin-immunoreactivity (irAP) was detected in neurons and cell processes of the supraoptic nucleus (SO), paraventricular nucleus (PVH), accessory neurosecretory nuclei (Acc) and suprachiasmatic nucleus. Strongly labeled cells/processes were noted in the internal layer of the median eminence, infundibular stem, anterior and posterior pituitary. Double-labeling the sections with goat polyclonal neurophysin I-antiserum and rabbit polyclonal apelin-antiserum revealed a population of magnocellular neurons in the PVH, SO and Acc expressing both irAP and neurophysin I-immunoreactivity (irNP), the latter being a marker of oxytocin-containing neurons. By inference, the AP-positive but irNP-negative magnocellular neurons could be vasopressin-containing. The presence of irAP in certain hypothalamic nuclei and pituitary suggests that the peptide may be a signaling molecule released from the hypothalamic-hypophysial axis.

No description available.