Intercalation of swallow and breathing recorded optically in the sagittally‐sectioned rat hindbrain

Abstract

The ventral respiratory column (VRC) contains heterogeneous neurons that generate and regulate respiration as well as other orofacial behaviors. In neonate SD rat, the VRC extends over 2 mm from the rostral margin of the facial nucleus (VIIn). In addition, networks that modulate breathing on a cycle‐to‐cycle basis are distributed along the dorsomedial margin of brainstem in or near the nucleus tractus solitaries (NTS): these include central networks that intercalate swallow into the respiratory pattern, and the first synapse of lung mechanoreceptors responsible for the Breuer‐Hering (BH) reflex. Both the VRC and NTS are exposed at the surface of the sagittaly‐sectioned rat hindbrain preparation (SSRH), enabling the induction of swallowing, as well as BH via bipolar electrode stimulation. Using previously‐described methods, coupling relations between VRC respiratory neurons before and during induced swallow and BH were obtained via high‐speed optical recordings along the entire VRC. Fluctuations in [Ca2+]I were detected using the medium‐affinity membrane permeant indicator fluo‐8L (KD=1.86 □M, AAT labs). Datasets were aligned using the caudal pole of the VIIn (VIIc) and the minimum of the concavity of the ventral surface at VIIc as rostrocaudal and ventrodorsal landmarks. Importantly this preparation allows for experimental conditions, which can directly test hypothesis related to swallow‐breathing coordination, and identify novel populations of neurons not currently recognized in the swallow central pattern generator.Support or Funding InformationThis work was supported by NIH grants HL 111215, HL 103415 and OT20D001983, the Craig F. Neilson Foundation Pilot Research Grant 546714, Kentucky Spinal Cord and Head Injury Research Trust, and the Commonwealth of Kentucky Challenge for Excellence.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.