Abstract
The superior cervical ganglion (SCG) sends sympathetic input to the carotid body (CB) via the ganglioglomerular nerve (GGN) in order to modulate carotid sinus nerve (CSN) chemosensory afferent discharge via controlling vascular tone. This chemoafferent discharge is then relayed to the nucleus tractus solitarius (NTS) where the information is processed resulting in a compensatory increase in respiration. Hypoxic gas challenge stimulates the GGN. However, little is known as to the effects of ganglioglomerular nerve transection (GGNx) on carotid body chemosensory afferent response to hypoxia (HX).Our objective was to determine the effect of unilateral GGNx on the ventilatory responses elicited by HX (10% O2, 90% N2) gas challenge (5 episodes of 5 min in duration separated by 15 min) in freely‐moving juvenile (P25) Sprague‐Dawley rats.Male rats postnatal (P) 21 were subjected to sham or unilateral (right or left) GGNx and were allowed 4 days to recover. On the day of the experiment, P25 rats were placed in whole‐body plethysmography chambers and subjected to the hypoxic gas exposure. Ventilatory parameters included frequency of breathing, tidal volume, minute ventilation (= frequency x tidal volume), inspiratory and expiatory times, end inspiratory and expiratory pauses, peak inspiratory and expiratory flows, inspiratory and expiratory drive, EF50 (expiratory flow at 50% expired tidal volume) and rejection index (percentage of abnormal breaths).The HX challenge elicited altered ventilatory responses in sham‐operated rats compared to unilateral GGNx. Rejection Index (%) was diminished in unilateral (left and right) GGNx rats compared to sham, in addition to Rpef in only the right GGNx rats. Peak inspiratory flow (mL/s) was increased in only left GGNx rats, while the peak expiratory flow (mL/s) rates were increased in both the right and left GGNx subjects. Minute ventilation (mL/min) exhibited ventilatory roll‐off in sham animals while no such trend was observed in left GGNx rats. Although peak inspiratory flow, inspiratory drive (mL/s), and expiratory drive (mL/s) reached similar plateaus in right GGNx, the onset of the responses was delayed when compared to their sham counterparts. End expiratory pause (msec) showed a more robust response following hypoxic challenge in right GGNx when viewed against the sham. These findings follow a similar trend to those previously demonstrated from unilateral SCG removal, but still possess characteristics that are unique to the GGN alone. This which suggests the role the SCG has in modulating the hypoxic response is through the GGN and the CB, as well as other yet unknown mechanisms.Support or Funding InformationNIH SPARC 1OT2OD023860‐02 SJLewisThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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