A modulatory role for oxygen in shaping rhythmic motor output patterns of neuronal networks

It is becoming increasingly evident that O₂-uptake in animal tissue is not only devoted to energy production. Here we review recent findings on a novel role of tissue oxygenation, notably in controlling the operation of neuronal networks in the central nervous system. Electrophysiological recordings in vivo and in vitro from rhythmically-active motor pattern generating networks in the lobster stomatogastric ganglion (STG) have revealed that oxygen is able to act in a manner equivalent to a classical neuromodulator. Local P_O2 variations within the low, but physiological range of 1–6 kPa are able to shape ongoing activity of these networks and therefore the motor behaviours in which they are involved. Oxygen's contribution to two of these, feeding and moulting, have been investigated. Importantly, the P_O2 effects are not related to hypoxic depression but are highly specific in terms of the network, neuron and even the synapse targeted. Our results are discussed in terms of functional significance and new research directions for mammalian physiology.