Effect of Cervical Sympathetic Chain Stimulation on Upper Airway Pressure is Dependent on Direct Post‐Ganglionic Innervation from the Superior Cervical Ganglion

Abstract

BACKGROUNDWe have previously demonstrated that cervical sympathetic chain (CSC) stimulation improves airway patency in Zucker Fat rats (model of concentric airway collapse). Anatomical studies reveal the presence of two major post‐ganglionic projections to the head and neck arising from the superior cervical ganglion (External Carotid Nerve (ECN) and Internal Carotid Nerve (ICN)), however, their functional contribution to improve upper airway patency is unclear.AIMWe sought to investigate the contribution of the CSC‐SCG‐ECN and CSC‐SCG‐ICN pathways on lowering upper airway pressure (UAP) and cardiorespiratory systems.METHODSUrethane‐anaesthetized healthy male Sprague‐Dawley (SD) rats and pathological Zucker Fat (ZF) rats were used to measure UAP, ECG, blood pressure and diaphragmatic EMG while the intact CSC was stimulated (bilaterally and unilaterally). CSC stimulation mediated effects on UAP and cardiorespiratory parameters were then assessed following systematic transection of ECN and ICN branches.RESULTSWe present two novel findings. Firstly, in all cases of CSC stimulation (SD control UAP (mmHg): −27% bilateral, −20% right, −6% left; ZF control UAP (mmHg): −34% bilateral, −19% right, −22% left), ECN denervation had no significant effect on UAP reductions or hemodynamics in both healthy and disease rats. Secondly, bilateral denervation of the ICN abolished CSC mediated UAP reductions, while leaving hemodynamic effects intact. UAP mediated effects via unilateral CSC stimulation were of ipsilateral origin, as contralateral ICN denervation prior to ipsilateral denervation had no effect. Little to no impact of laterality of CSC stimulation and ICN transection was seen in hemodynamics or diaphragmatic EMG.CONCLUSIONFor the first time, we have demonstrated that CSC stimulation reductions on upper airway pressure are dependent on ipsilateral post‐ganglionic innervation via the ICN. However, the lack of effect on hemodynamics remains to be defined.Support or Funding InformationNIH1OT2OD023860‐01, Galvani BioelectronicsThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.