Lesion of Serotonergic Afferents to the Retrotrapezoid Nucleus Impairs the Tachypneic Response to Hypercapnia in Unanesthetized Animals

Autor(es)

Leirao, Isabela P. ^[1] ; Colombari, Debora S. A. ^[1] ; da Silva, Glauber S. F. ^[2] ; Zoccal, Daniel B. ^[1]

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ UNESP, Dept Physiol & Pathol, Sch Dent, Araraquara, SP - Brazil

^[2] Fed Univ Minas Gerais ICB UFMG, Dept Physiol & Biophys, Inst Biol Sci, Belo Horizonte, MG - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Neuroscience; v. 452, p. 63-77, JAN 1 2021.
• Citações Web of Science: 0

Resumo

Hypercapnia promotes an increase in pulmonary ventilation due to the stimulation of brainstem chemosensory cells that are connected to the respiratory network. Among these cells are the raphe serotonergic neurons which widely send projections to distinct central respiratory compartments. Nevertheless, the physiological role of specific raphe serotonergic projections to other chemosensitive sites on the emergence of hypercapnia ventilatory response in vivo still remains to be elucidated. Here we investigated whether the ventilatory response to hypercapnia requires serotonergic inputs to the chemosensitive cells of the retrotrapezoid nucleus (RTN) in the ventrolateral medulla. To test this, pulmonary ventilation was evaluated under baseline conditions and during hypercapnia (7% CO2) in unanesthetized juvenile Holtzman rats (60-90 g) that received bilateral microinjections of either vehicle (control) or anti-SERT-SAP (0.1 mM, 10 pmol/100 nl) toxin in the RTN to retrogradely destroy serotonergic afferents to this region. Fifteen days after microinjections, baseline ventilation was not different between anti-SERT-SAP (n = 8) and control animals (n = 9). In contrast, the ablation of RTN-projecting serotonergic neurons markedly attenuated the hypercapnia-induced increase in respiratory frequency which was correlated with reduced numbers of serotonergic neurons in the raphe obscurus and magnus, but not in the raphe pallidus. The increase in tidal volume during hypercapnia was not significantly affected by anti-SERT-SAP microinjections in the RTN. Our data indicate that serotoninergic neurons that send projections to the RTN region are required for the processing of ventilatory reflex response during exposure to high CO2 in unanesthetized conditions. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 18/21000-2 - Mecanismos iônicos recrutados durante a resposta ventilatória ao ATP: entendendo a interação entre sensores centrais para oxigênio e os neurônios geradores do ritmo respiratório
• Beneficiário: Daniel Breseghello Zoccal
• Modalidade de apoio: Bolsas no Exterior - Pesquisa
• Processo FAPESP: 13/17251-6 - Mecanismos neurais de geração do padrão respiratório e do acoplamento simpático-respiratório em condições de hipóxia
• Beneficiário: Daniel Breseghello Zoccal
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 18/04439-0 - Avaliação funcional da interação entre os núcleos da rafe e o núcleo retrotrapezóide no padrão respiratório e nas respostas ventilatórias à hipercapnia em ratos
• Beneficiário: Isabela de Paula Leirão
• Modalidade de apoio: Bolsas no Brasil - Mestrado