Loss of ganglioglomerular nerve input to the carotid body impacts the hypoxic ventilatory response in freely-moving rats

Paulina M Getsy; Gregory A Coffee; Stephen J Lewis

doi:10.3389/fphys.2023.1007043

Loss of ganglioglomerular nerve input to the carotid body impacts the hypoxic ventilatory response in freely-moving rats

Front Physiol. 2023 Mar 16:14:1007043. doi: 10.3389/fphys.2023.1007043. eCollection 2023.

Authors

Paulina M Getsy¹, Gregory A Coffee¹, Stephen J Lewis^{1

2

3}

Affiliations

¹ Department of Pediatrics, Division of Pulmonology, Allergy and Immunology, Case Western Reserve University, Cleveland, OH, United States.
² Department of Pharmacology, Case Western Reserve University, Cleveland, OH, United States.
³ Functional Electrical Stimulation Center, Case Western Reserve University, Cleveland, OH, United States.

Abstract

The carotid bodies are the primary sensors of blood pH, pO₂ and pCO₂. The ganglioglomerular nerve (GGN) provides post-ganglionic sympathetic nerve input to the carotid bodies, however the physiological relevance of this innervation is still unclear. The main objective of this study was to determine how the absence of the GGN influences the hypoxic ventilatory response in juvenile rats. As such, we determined the ventilatory responses that occur during and following five successive episodes of hypoxic gas challenge (HXC, 10% O₂, 90% N₂), each separated by 15 min of room-air, in juvenile (P25) sham-operated (SHAM) male Sprague Dawley rats and in those with bilateral transection of the ganglioglomerular nerves (GGNX). The key findings were that 1) resting ventilatory parameters were similar in SHAM and GGNX rats, 2) the initial changes in frequency of breathing, tidal volume, minute ventilation, inspiratory time, peak inspiratory and expiratory flows, and inspiratory and expiratory drives were markedly different in GGNX rats, 3) the initial changes in expiratory time, relaxation time, end inspiratory or expiratory pauses, apneic pause and non-eupneic breathing index (NEBI) were similar in SHAM and GGNX rats, 4) the plateau phases obtained during each HXC were similar in SHAM and GGNX rats, and 5) the ventilatory responses that occurred upon return to room-air were similar in SHAM and GGNX rats. Overall, these changes in ventilation during and following HXC in GGNX rats raises the possibility the loss of GGN input to the carotid bodies effects how primary glomus cells respond to hypoxia and the return to room-air.

Keywords: carotid body; ganglioglomerular nerve; hypoxic challenge; juvenile rats; ventilatory parameters.

Grants and funding

These studies were funded by the NIH/SPARC grant 10T20D023860 (Functional Mapping of the afferent and Efferent Projections of the Superior Cervical Ganglion Interactome in normal healthy Sprague-Dawley rats) awarded to SJL.