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The 3‐2‐1 state respiratory rhythm generator hypothesis revealed by microsectioning, reduced extracellular chloride and alterations in arterial gas tensions in the in situ rat
Journal article   Open access   Peer reviewed

The 3‐2‐1 state respiratory rhythm generator hypothesis revealed by microsectioning, reduced extracellular chloride and alterations in arterial gas tensions in the in situ rat

Ana Paula Lima Abdala, Hidehiko Koizumi, Ilya A. Rybak, Jeffrey C. Smith and Julian F.R. Paton
The FASEB journal, v 21(5), pp A557-A558
Apr 2007
DOI: https://doi.org/10.1096/fasebj.21.5.A557-e
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https://doi.org/10.1096/fasebj.21.5.a557-eView
Published, Version of Record (VoR)Open Access (License Unspecified),  Open

Abstract

We proposed that the pre‐Bötzinger complex (pBC), a region generating inspiratory (I) activity in vitro, is embedded within a pontomedullary network in the intact animal. We tested if the pBC, Bötzinger complex (BC) and pons represent distinct functional compartments with a hierarchical organization. Using the in situ arterially perfused rat preparation, which preserves the pontomedullary respiratory network, phrenic (P), central vagal (X), hypoglossal (XII) and abdominal (AB) nerves were recorded. In the intact system, a 3‐phase rhythm was observed with ramp‐inspiratory pattern in P, X and XII, with post‐inspiratory (PI) discharge in X and AB. Pontine transection, reducing chloride (75%), or exposing to hypocapnia (3–4%CO2), induced a 2‐phase rhythm. P, XII and X exhibited square‐wave inspiratory discharge, PI activity in X was absent and AB discharged throughout expiration. The frequency of this 2‐phase I–E rhythm was not affected by riluzole (10μM), a blocker of persistent sodium channels. Removal of the BC or exposure to hypocapnia/hypoxia (3%CO2, 40%O2), resulted in a pBC‐generated 1‐phase rhythm, (with no AB activity), the frequency of which was riluzole‐sensitive. We conclude that the pons, BC, and pBC have a hierarchical spatial and functional organization reflected mechanistically by distinct 3, 2 and 1 phase rhythms reflecting different functional states. Support: CRCNS and the IRP of NINDS, NIH.

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