Blockade of synaptic inhibition within the pre‐Bötzinger complex in the cat suppresses respiratory rhythm generation in vivo

• Published in: The Journal of physiology 1998-05, Vol.509 (1), p.245-254
• Main Authors: Pierrefiche, O., Schwarzacher, S. W., Bischoff, A. M., Richter, D. W.
• Format: Article
• Language: English
• Subjects: 8-Hydroxy-2-(di-n-propylamino)tetralin - pharmacology; Animals; Bicuculline - pharmacology; Cats; Female; GABA Antagonists - administration & dosage; GABA Antagonists - pharmacology; GABA-A Receptor Antagonists; Glycine Agents - pharmacology; Male; Medulla Oblongata - drug effects; Medulla Oblongata - physiology; Microinjections; Original; Phrenic Nerve - drug effects; Phrenic Nerve - physiology; Receptors, Glycine - antagonists & inhibitors; Respiratory Mechanics - drug effects; Respiratory Mechanics - physiology; Serotonin Receptor Agonists - pharmacology; Strychnine - pharmacology; Synapses - drug effects; Synapses - physiology; Tetrodotoxin - pharmacology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.1998.245bo.x

1 The role of synaptic inhibition in respiratory rhythm generation was analysed by microinjections of GABAA and glycine receptor antagonists into the bilateral pre‐Bötzinger complex (PBC) of anaesthetized cats. Central respiratory activity was monitored by phrenic nerve recordings. 2 Bilateral injections of bicuculline (50 or 100 μm) irreversibly slowed respiratory frequency and induced apneustic patterns. 3 Bilateral injections of strychnine (50 or 100 μm) greatly reduced phrenic burst amplitudes leading to increased burst frequency or irreversibly blocked rhythmic phrenic discharges. After unilateral tetrodotoxin (TTX) blockade in the PBC, strychnine injection into the contralateral PBC blocked rhythmic phrenic discharges. 4 Bilateral blockade of both GABAergic and glycinergic inhibition abolished rhythmic burst discharges and only tonic phrenic activity remained. Such tonic activity was blocked only by TTX (1 μm). 5 Potentiation of synaptic inhibition by the serotonin 1A receptor agonist 8‐hydroxydipropylaminotetralin (8‐OH‐DPAT; 50 μm) restored rhythmic activity only when given shortly after strychnine and bicuculline applications. It was, however, ineffective after blockade of synaptic inhibition was complete. 6 The study demonstrates the significance of synaptic inhibition in the process of respiratory generation in the adult cat in vivo .