Peripheral chemoreflex activation induces expiratory but not inspiratory excitation of C1 pre-sympathetic neurones of rats

Author(s)

da Silva, Melina P. ; Spiller, Pedro F. ; Paton, Julian F. R. ; Moraes, Davi J. A.

• Document type: Journal article
• Source: ACTA PHYSIOLOGICA; v. N/A, p. 22-pg., 2022-06-28.

Abstract

Aims Stimulation of peripheral chemoreceptors, as during hypoxia, increases breathing and respiratory-related sympathetic bursting. Activation of catecholaminergic C1 neurones induces sympathoexcitation, while its ablation reduces the chemoreflex sympathoexcitatory response. However, no study has determined the respiratory phase(s) in which the pre-sympathetic C1 neurones are recruited by peripheral chemoreceptor and whether C1 neurone activation affects all phases of respiratory modulation of sympathetic activity. We addressed these unknowns by testing the hypothesis that peripheral chemoreceptor activation excites pre-sympathetic C1 neurones during inspiration and expiration. Methods Using the in situ preparation of rat, we made intracellular recordings from baroreceptive pre-sympathetic C1 neurones during peripheral chemoreflex stimulation. We optogenetically activated C1 neurones selectively and compared any respiratory-phase-related increases in sympathetic activity with that which occurs following stimulation of the peripheral chemoreflex. Results Activation of peripheral chemoreceptors using cytotoxic hypoxia (potassium cyanide) increased the firing frequency of C1 neurones and both the frequency and amplitude of their excitatory post-synaptic currents during the phase of expiration only. In contrast, optogenetic stimulation of C1 neurones activates inspiratory neurones, which secondarily inhibit expiratory neurones, but produced comparable increases in sympathetic activity across all phases of respiration. Conclusion Our data reveal that the peripheral chemoreceptor-mediated expiratory-related sympathoexcitation is mediated through excitation of expiratory neurones antecedent to C1 pre-sympathetic neurones; these may be found in the Kolliker-Fuse nucleus. Despite peripheral chemoreceptor excitation of inspiratory neurones, these do not trigger C1 neurone-mediated increases in sympathetic activity. These studies provide compelling novel insights into the functional organization of respiratory-sympathetic neural networks. (AU)

• FAPESP's process: 21/06886-7 - Role of purinergic receptors in the carotid body in heart failure
• Grantee: Davi José de Almeida Moraes
• Support Opportunities: Research Grants - Young Investigators Grants - Phase 2
• FAPESP's process: 19/11863-6 - Synaptic transmission and electrophysiological properties of bronchial motoneurons of the dorsal motor nucleus of the vagus from rats
• Grantee: Davi José de Almeida Moraes
• Support Opportunities: Regular Research Grants
• FAPESP's process: 20/03955-5 - Effects of sustained hypoxia on the electrophysiological properties and purinergic signaling of the carotid chemoreceptors of rats
• Grantee: Pedro Favoretto Spiller
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 18/07027-5 - Role of astrocytes in the excitability of magnocelular neurons form supraoptic nucleus during changes in the plasma osmolality
• Grantee: Melina Pires da Silva
• Support Opportunities: Research Grants - Young Investigators Grants