Cholinergic mechanisms of the intermediate nucleus of the solitary tract involved in the cardiorespiratory responses of the Hering-Breuer reflex

• Grant number: 16/02725-0
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): June 01, 2016
• Effective date (End): August 31, 2016
• Field of knowledge: Biological Sciences - Physiology
• Principal Investigator: Débora Simões de Almeida Colombari
• Grantee: Werner Issao Furuya
• Supervisor abroad: Mathias Dutschmann
• Home Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Local de pesquisa : University of Melbourne, Australia
• Associated to the scholarship: 13/22526-4 - Cholinergic function of commissural nucleus of the solitary tract on cardiorespiratory responses to hypoxia, hypercapnia and pH decrease, BP.DR

Abstract

The nucleus of the solitary tract (NTS) is the primary synaptic site of different visceral afferents, including the baroreceptors. A functional cholinergic system has been described in the NTS. Microinjection of acetylcholine (ACh) or the muscarinic agonist carbachol into the intermediate NTS (iNTS) of anaesthetized or awake rats induces dose-dependent baroreflex-like hypotensive and bradycardic responses. Similar responses are also produced by nicotinic receptor activation in the iNTS. In previous studies from our laboratory, we have shown that microinjection of ACh in the iNTS in the in situ preparation induced a sympatho-inhibitory response combined with a decrease in the phrenic nerve activity (PNA). Although, the antagonism of nicotinic receptors in the iNTS abolished the reduction of sympathetic nerve activity (SNA) and PNA induced by ACh in the iNTS, neither muscarinic nor nicotinic antagonist injected in the iNTS changed the baroreflex responses. This may suggest that ACh induces SNA changes acting on pathways not related to baroreflex function. Activation of the Hering-Breuer reflex induces a decrease in SNA and in PNA, a response similar to the one observed after ACh injection in the iNTS. Thus, it is possible that the cholinergic mechanisms in the iNTS are involved with this reflex. Therefore, in this study we intend to investigate the involvement of muscarinic and nicotinic receptors of the iNTS on PNA and SNA responses to Hering-Breuer reflex activation.