German wine and respiration: Remarks on the discovery, properties and significance of the Bötzinger complex

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The Bötzinger complex (BötC) comprises a distinct bilateral group of interneurons that are active during the expiratory phase of the respiratory cycle, located in the rostral medulla ventral to the compact formation of the nucleus ambiguus. It was named after the bottles of wine served at the conference dinner of an international meeting held in Germany in 1980, where the first electrophysiological data describing these neurons were presented. In cats, BötC neurons predominantly exhibit an augmenting (E‐Aug) firing pattern, whereas in rats E‐Aug and E‐Dec (decrementing expiratory) patterns are observed. Both subtypes issue axons that often extensively arborise on both sides of the medulla, forming inhibitory glycinergic and/or GABAergic synapses with inspiratory neurons of the dorsal and ventral respiratory groups. Additionally, E‐Aug neurons project to the spinal cord and inhibit phrenic motoneurons. These properties contrast with those of another group of bulbospinal expiratory neurons in the caudal medulla, which do not issue medullary axon collaterals and are excitatory. BötC neurons regulate the interval during which inspiratory neurons remain silent and contribute to synchronisation of respiratory activity across both sides of the lower brainstem. Recent in vivo , reduced‐preparation and in silico studies indicate that they also contribute to respiratory rhythmogenesis through mutual inhibitory synaptic interactions with the pre‐Bötzinger complex. This review provides the history of the discovery and naming of the BötC and a detailed discussion of the properties of BötC neurons, including their location, morphology, afferent and efferent axonal projections, synaptic connectivity and functional role.