Recovery of respiratory motor function after repeated exposure to intermittent hypoxia in mice genetically depleted of brain serotonin (1178.8)

Abstract

Purpose: Our study was designed to determine if daily exposure to intermittent hypoxia (IH) promotes recovery of respiratory motor function in mice following spinal cord hemisection and to determine if serotonin in the central nervous system is required to induce this process.Methods: Telemetry transmitters were surgically implanted in 9 wild type mice (Tph2+/+) and 6 tryptophan hydroxylase 2 knockout mice (Tph2‐/‐) to measure electroencephalography, core body temperature and activity. Thereafter, a C2 hemisection was completed. Following recovery mice were exposed to 12 ‐ 4 minute episodes of hypoxia (10% oxygen) for 10 consecutive days while measures of ventilation were monitored via whole body plethysmography.Results: Following 10 days of exposure to IH, tidal volume (VT) and ventilatory drive (VD) were enhanced compared to baseline measures on the initial day in the Tph2‐/‐ but not the Tph2+/+ mice (VT ‐ 1.25 ± 0.08 vs. 0.97 ± 0.03, p = 0.001; VD ‐ 1.28 ± 0.11 vs. 0.97 ± 0.04, p = 0.001; standardized to baseline on initial day), while breathing frequency was reduced in both groups (0.92 ± 0.04 vs. 0.92 ± 0.04, p = 0.02; standardized to baseline on initial day).Conclusion: Recovery of respiratory motor function in spinal cord hemisected mice following repeated daily exposure to IH does not require central nervous system serotonin.Grant Funding Source: Supported by VA award 1IO1 RX000458 (DMK) & 1I21RX001412 (JHM)