0050 Glossopharyngeal Nerve Discharge Patterns in Neuromuscular Control of Breathing

Abstract Introduction The glossopharyngeal nerve is important for gas exchange in fish, but in mammals concentration is focused on the hypoglossal nerve (Dewald et al, 2018). In the present study, we hypothesize the discharge pattern of glossopharyngeal nerve activity (GPNA) will relate to the 3-phase respiratory motor pattern apparent in the vagal, hypoglossal, and phrenic nerves in mammals. Methods We recorded GPNA from in situ arterially perfused brainstem preparations of juvenile rats (n=10) and compared these data to simultaneously recorded phrenic (PNA), vagal (VNA), and hypoglossal (HNA) nerve activities. We report the timing of GPNA relative to onset and duration of PNA, HNA, and VNA for at least 32 respiratory cycles in each preparation. Results Preparations had a eupnea-like 3-phase respiratory motor pattern (Dutschmann et al 2009). The average respiratory cycle length was 4.30s ± 0.61 (Mean±SD). The inspiratory discharge duration analyzed from PNA was 0.73s ± 0.15; the postinspiratory discharge duration analyzed from VNA, 2.85s ± 0.69; and a late expiratory phase duration, 0.87s ± 0.46. The GPNA started significantly before the onset of PNA with a pre-inspiratory discharge duration of 0.53s ± 0.23 (ANOVA p=0.0001). Overall the pre-inspiratory discharge of GPNA was similar compared to pre-inspiratory discharge of HNA (0.36s ± 0.21), postinspiratory discharge duration of GPNA (0.53s ± 0.12) was also comparable to HNA (0.59s ± 0.26), but significantly shorter compared to VNA (2.85s ± 0.69; p=0.0001). Conclusion Both GPNA and HNA displayed robust, characteristic pre-inspiratory/inspiratory discharge patterns in every preparation. Clinically, the activation pattern of the GPNA may be as crucial as that of the HNA, for maintaining a healthy, patent upper airway for breathing during sleep. Support (if any) The Japanese Respiratory Society Fellowship Grants, NIH/NHLBI