Norepinephrine reconfigures post‐inspiratory neurons within the pre‐Bötzinger complex of mice

Abstract

The contribution of inspiratory neurons in central inspiratory rhythmogenesis is well established. However, the inspiratory neuronal phenotype is only one of several known to be present in the ventral respiratory column and the pre‐Bötzinger complex (preBötC), in particular. Here we characterized post‐inspiratory neurons (post‐In) in rhythmic transverse brainstem slices (550–620μm, mice P2–P12). Pharmacological and electrophysiological characterizations reveal that post‐In receive concurrent excitatory and inhibitory synaptic input in‐phase with the inspiratory population rhythm in the preBötC. This concurrent input allows post‐In to become conditional inspiratory neurons (In) in the presence of decreased synaptic inhibition. We also find that elevated noradrenergic tone (NE) transforms the firing patterns of some post‐In into conditional In. Optogenetic experiments made in ChAT‐positive neurons expressing channelrhodopsin 2 revealed that ChAT‐positive neurons with the post‐In phenotype are not transformed into In by NE, suggesting that it is non‐cholinergic preBötC interneurons that are characterized by this conditional phenotype. Our findings illustrate that concurrent inhibition and excitation characterizes post‐In in the preBötC and that the post‐In phenotype can be reconfigured by the presence of elevated NE.