Serotonina e controle respiratório de frangos (Gallus gallus domesticus)
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Data
2018-11-30
Autores
Santos, Kassia Moreira
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Universidade Estadual Paulista (Unesp)
Resumo
Variações na PCO2/pH sanguíneo em vertebrados são detectadas, principalmente, pelos quimiorreceptores centrais. Em aves, os tipos de neurônios quimiossensíveis intermediadores da resposta ventilatória não são conhecidos, assim como sua localização. Por outro lado, em mamíferos, sabe-se que estes quimiorreceptores compreendem uma grande população neuronal e estão distribuídos no sistema nervoso central. Dentre os tipos de quimiorreceptores centrais, em mamíferos, destacam-se os neurônios serotoninérgicos (5-HT) contidos em elevada concentração na rafe e que possuem projeções às principais regiões envolvidas na regulação da respiração. A partir do exposto, objetivou-se verificar a participação da serotonina no controle respiratório de frangos. Foram utilizados pintos carijós machos e fêmeas, em dois conjuntos experimentos com abordagem distintas que propuseram reduzir o conteúdo de serotonina liberado no espaço sináptico em resposta à hipercapnia e à hipóxia. O primeiro com deleção química dos neurônios 5-HT, mediante a injeção de 1µL de anti-SERT-SAP (0,1µM) no quarto ventrículo (4V), os grupos controle receberam injeções de PBS e IgG-SAP. O segundo experimento por inibição da biossíntese de serotonina pela p-clorofenilalanina (PCPA) em 100mg/kg i.p. (animais controles receberam salina 0,9% ou solução veículo). O anti-SERT-SAP reduziu o número de neurônios 5-HT no rombencéfalo dos pintos (P<0,05). Os animais anti-SERT-SAP apresentaram menor frequência respiratória (FR) que os controles em ar ambiente (P<0,05). Quando foram expostos à hipercapnia de 7%, a ventilação (VE) desses animais foi atenuada, sendo associada a menor FR apresentada pelos mesmos (P<0,05). O volume corrente (VT) não diferiu entre os tratamentos em hipercapnia (P>0,05). Quando os animais foram expostos à hipercapnia associada à hiperóxia, onde a quimiorrecepção periférica foi silenciada, a resposta à hipercapnia não foi identificada, demonstrando que a ação dos neurônios serotoninérgicos em frangos pode ser dependente da quimiorrecepção periférica. A deleção dos neurônios 5-HT não influenciou a resposta ventilatória à hipóxia (P>0,05). A PCPA reduziu a utilização da 5-HT na rafe e coluna respiratória do bulbo dos pintos (P<0,05). Esses animais tiveram a FR atenuada em ar ambiente (P<0,05). A menor taxa de 5-HT metabolizada encontrada não foi suficiente para mostrar seu papel na resposta ventilatória de frangos à hipercapnia visto que estes animais não diferiram dos animais que receberam solução veículo (P>0,05). Não houve diferença significativa entre os tratamentos para os parâmetros mensurados em hipóxia (P>0,05). De acordo com os resultados conclui-se que a serotonina apresenta um papel tônico excitatório no controle da frequência respiratória de frangos. E os neurônios serotoninérgicos participam da resposta ventilatória à hipercapnia, com dependência das aferências dos quimiorreceptores periféricos. Estes neurônios não participam da resposta ventilatória à hipóxia em frangos.
Variations in PCO2/pH blood in vertebrates are mainly detected by central chemoreceptors. In birds, the types of chemosensitive neurons mediating the ventilatory response are not known, as is their location. On the other hand, in mammals, it is known that these chemoreceptors comprise a large neuronal population and are distributed in the central nervous system. Among the types of central chemoreceptors in mammals, serotoninergic (5-HT) neurons are found in high concentration in the raphe and have projections to the main regions involved in the regulation of respiration. From the above, we aimed to verify the participation of serotonin in respiratory control of broilers. Male and female carybush chicks were used in two sets with distinct approaches that proposed to reduce the serotonin content released in the synaptic space in response to hypercapnia and hypoxia. The first with chemical deletion of 5-HT neurons, by injecting 1μL of anti-SERT-SAP (0.1μM) into the fourth ventricle (4V), the control groups received injections of PBS and IgG-SAP. The second experiment by inhibition of serotonin biosynthesis by p-chlorophenylalanine (PCPA) at 100mg/ kg i.p. (control animals received 0.9% saline or vehicle solution). Anti-SERT-SAP reduced the number of 5-HT neurons in the hindbrain of chicks (P <0.05). Anti-SERT-SAP animals presented lower respiratory rate (RF) than controls in ambient air (P<0.05). When they were exposed to hypercapnia of 7%, the ventilation (VE) of these animals was attenuated, being associated with the lower FR presented by them (P<0.05). The tidal volume (VT) did not differ between treatments in hypercapnia (P>0.05). When the animals were exposed to hypercapnia associated with hyperoxia, where peripheral chemoreception was silenced, the response to hypercapnia was not identified, demonstrating that the action of serotonergic neurons in chickens may be dependent on peripheral chemoreception. Deletion of 5-HT neurons did not influence the ventilatory response to hypoxia (P> 0.05). PCPA reduced the use of 5-HT in the medullary raphe and respiratory column of the chick (P <0.05). These animals had the FR attenuated in room air (P<0.05). The lower metabolised 5-HT rate found was not sufficient to show its role in the ventilatory response of broilers to hypercapnia since these animals did not differ from the animals receiving vehicle solution (P>0.05). There was no significant difference between treatments for the parameters measured in hypoxia (P>0.05). According to the results, it is concluded that serotonin presents an excitatory tonic role in controlling the respiratory rate of chickens. The serotonergic neurons participate in the ventilatory response to hypercapnia, with dependence on peripheral chemoreceptor afferents. These neurons do not participate in the ventilatory response to hypoxia in chickens.
Variations in PCO2/pH blood in vertebrates are mainly detected by central chemoreceptors. In birds, the types of chemosensitive neurons mediating the ventilatory response are not known, as is their location. On the other hand, in mammals, it is known that these chemoreceptors comprise a large neuronal population and are distributed in the central nervous system. Among the types of central chemoreceptors in mammals, serotoninergic (5-HT) neurons are found in high concentration in the raphe and have projections to the main regions involved in the regulation of respiration. From the above, we aimed to verify the participation of serotonin in respiratory control of broilers. Male and female carybush chicks were used in two sets with distinct approaches that proposed to reduce the serotonin content released in the synaptic space in response to hypercapnia and hypoxia. The first with chemical deletion of 5-HT neurons, by injecting 1μL of anti-SERT-SAP (0.1μM) into the fourth ventricle (4V), the control groups received injections of PBS and IgG-SAP. The second experiment by inhibition of serotonin biosynthesis by p-chlorophenylalanine (PCPA) at 100mg/ kg i.p. (control animals received 0.9% saline or vehicle solution). Anti-SERT-SAP reduced the number of 5-HT neurons in the hindbrain of chicks (P <0.05). Anti-SERT-SAP animals presented lower respiratory rate (RF) than controls in ambient air (P<0.05). When they were exposed to hypercapnia of 7%, the ventilation (VE) of these animals was attenuated, being associated with the lower FR presented by them (P<0.05). The tidal volume (VT) did not differ between treatments in hypercapnia (P>0.05). When the animals were exposed to hypercapnia associated with hyperoxia, where peripheral chemoreception was silenced, the response to hypercapnia was not identified, demonstrating that the action of serotonergic neurons in chickens may be dependent on peripheral chemoreception. Deletion of 5-HT neurons did not influence the ventilatory response to hypoxia (P> 0.05). PCPA reduced the use of 5-HT in the medullary raphe and respiratory column of the chick (P <0.05). These animals had the FR attenuated in room air (P<0.05). The lower metabolised 5-HT rate found was not sufficient to show its role in the ventilatory response of broilers to hypercapnia since these animals did not differ from the animals receiving vehicle solution (P>0.05). There was no significant difference between treatments for the parameters measured in hypoxia (P>0.05). According to the results, it is concluded that serotonin presents an excitatory tonic role in controlling the respiratory rate of chickens. The serotonergic neurons participate in the ventilatory response to hypercapnia, with dependence on peripheral chemoreceptor afferents. These neurons do not participate in the ventilatory response to hypoxia in chickens.
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Palavras-chave
Anti-sert-sap, Aves, Neurônios serotoninergicos, p-clorofenilalanina, Ventilação pulmonar, Anti-sert-sap, Birds, Serotonergic neurons, p-chlorophenylalanine, Pulmonary ventilation