Anoxia Response in Physiological Potassium of the Isolated Inspiratory Center in Calibrated Newborn Rat Brainstem Slices

Abstract

Using newborn rat brainstem-spinal cords, we were the first to show that medullary inspiratory networks can generate the neonatal biphasic (initial acceleration-secondary slowing) respiratory response to severe hypoxia causing tissue anoxia. Our findings also indicated that medullary inspiratory interneurons remain functional during sustained anoxia due to effective utilization of anaerobic metabolism. In that previous work by us and related studies by others on respiratory anoxia responses in the above en bloc model or brainstem slices, presumptive recording sites within the pre-Bötzinger complex (preBötC) inspiratory center were not histologically verified. Moreover, preBötC slices were studied in 7–9 mM K⁺ to stabilize rhythm which can, however, affect respiratory neuromodulation. Here, we summarize our previous findings on respiratory anoxia responses in the en bloc model in physiological (3 mM) K⁺. Using our recently developed ‘calibrated’ slices, we also exemplify anoxia effects in anatomically identified preBötC cells in physiological K⁺ based on recording electrophysiological population activity in conjunction with either membrane potential or cytosolic Ca²⁺.