Reconfiguration of the neural network controlling multiple breathing patterns: eupnea, sighs and gasps

Are different forms of breathing derived from one or multiple neural networ ks? We demonstrate that brainstem slices containing the pre-Botzinger compl ex generated two rhythms when normally oxygenated, with striking similariti es to eupneic ('normal') respiration and sighs. Sighs were triggered by eup neic bursts under control conditions, but not in the presence of strychnine (1 mu M). Although all neurons received synaptic inputs during both activi ties, the calcium channel blocker cadmium (4 mu M) selectively abolished si ghs. In anoxia, sighs ceased, and eupneic activity was reconfigured into ga sping, which like eupnea was insensitive to 4 mu M cadmium. This reconfigur ation was accompanied by suppression of synaptic inhibition. We conclude th at a single medullary network underlies multiple breathing patterns.