Spatiotemporal patterns of ventral medullary respiratory network activity during eupnea and gasping imaged using optical recording in situ

Abstract

We investigated changes in the spatiotemporal pattern of respiratory network activity in the ventrolateral medulla during eupnea and hypoxic-induced gasping in situ. Part of the rostral ventrolateral medulla was stained with a voltage-sensitive dye (Di-2 ANEPEQ) centered within, and adjacent to, the pre-Bötzinger complex, as defined by anatomic landmarks and from extracellular recording of respiratory related discharge. During eupnea, fluorescence initially increased prior to the onset of phrenic nerve activity and progressively intensified with inspiration peaking at the end of inspiration. During early expiration, fluorescence declined slowly throughout this phase. In contrast, when the respiratory pattern was shifted to gasping, only inspiratory fluorescence signals were observed. Regions active during gasping showed more intense fluorescence and there was a recruitment of additional medullary regions that were not active during eupnea. Closer examination of regions of peak fluorescence during eupnea and gasping revealed that these areas were distinct spatially. These results suggest that the shift in respiratory motor pattern from eupnea to gasping is associated with changes in the spatiotemporal organization of the ventrolateral medullary respiratory network. NIH and BHF funded research