A Peripheral Oxygen Sensor Provides Direct Activation of an Identified Respiratory CPG Neuron in Lymnaea

The mechanisms by which peripheral, hypoxia-sensitive chemosensory cells modulate the output from the respiratory central pattern generator (CPG) remain largely unknown. In order to study this topic at a fundamental level, we have developed a simple invertebrate model system, Lymnaea stagnalis wherein we have identified peripheral chemoreceptor cells (PCRCs) that relay hypoxiasensitive chemosensory information to a known respiratory CPG neuron, right pedal dorsal 1 (RPeD1). Significance of this chemosensory drive was confirmed via denervation of the peripheral sensory organ containing the PCRCs, and subsequent behavioral observation. This study provides evidence for direct synaptic connectivity between oxygen sensing PCRCs and a CPG neuron, and describes a unique model system appropriate for studying mechanisms of hypoxia-induced, respiratory plasticity from the level of an identified synapse to whole animal behavior.