Ascending projections of the nucleus retroambiguus target key areas of the ponto‐medullary respiratory network (714.1)

Abstract

Purpose: We aim to elucidate the role and contribution of the nucleus retroambiguus (NRA) in the generation of respiratory rhythm. We previously identified a putative rhythmogenic area 1.5 mm caudal to obex, destruction of which abolished respiratory rhythm in the in‐situ perfused brainstem‐spinal cord preparation of rat. Histological analysis indicated that the putative rhythmogenic cell population resides at the planar level of the pyramidal decussation, therefore likely to overlap with the NRA. We investigated possible involvement of the NRA in rhythm generation by mapping its neuronal connectivity in rat. Methods: Anterograde neuronal tracer, biotinylated dextran amine, was injected into the NRA. Respiratory areas in which labelled terminal fields were seen were injected with retrograde tracer Fast Blue in subsequent experiments. Results: Anterograde tracing from the NRA revealed dense clusters of labelled nerve terminals within important respiratory nuclei including the pre‐Bötzinger complex (PBC), parafacial respiratory group (pFRG) and Kölliker Fuse nucleus (KF). Injection of retrograde tracer into PBC, KF and pFRG show clusters of retrogradely labelled cell bodies in the NRA. Conclusion: Our data provides the anatomical framework for a rhythmogenic role of the NRA within the respiratory network.Grant Funding Source: ARC