An avian model for exploring brain stem rhythmogenic behavior during early development

Abstract

Brain‐related breathing problems are common in early life. Despite intensive investigations into mammalian breathing control, our understanding of respiratory rhythm generation is still unclear, especially during the prenatal period. We aim to develop the avian embryo as a more tractable prenatal model to study breathing related behaviors. Birds are highly active endotherms, like mammals, and provide access for manipulations that mammals cannot. In the rodent, automatic breathing behaviors have been identified in isolated transverse brainstem slices. We hypothesize that there is a similar complex within the avian brainstem. Thus, our goal is to identify the central pattern generator for breathing in the bird. We used an activity dependent dye, electrical recordings, and Nissl staining to generate a neuroanatomical brain stem map. We examined isolated brain stems from Corturnix japonica near internal pipping when breathing movements are present. Results suggest that birds possess a spontaneously generated rhythm in the ventral lateral medulla similar to mammals. We further show that in some preparations tonic activity became rhythmic when inhibitory neurotransmission was blocked. These results suggest critical differences between the prenatal development of central breathing control of bird and mammals, including the importance of GABA and glycine neurotransmission prior to parturition.