Baclofen eliminates cluster lung breathing of the tadpole brainstem, in vitro

Intermittent lung ventilation is a respiratory pattern wherein breaths occu r in clusters. Intermittent lung ventilation is common in amphibians and ca n occur in mammals. Isolated brainstems from postmetamorphic tadpoles exhib iting episodic lung ventilatory bursts were superfused with baclofen, a pot ent gamma-aminobutyric acid (GABA)(B) receptor agonist, At moderate concent rations (0.125 to 0.5 mu M), the number of lung bursts per episode decrease d but their overall frequency was unchanged. At 0.5 mu M, only 1.22 +/- 0.2 4 lung bursts occurred per episode, indicating virtually no clustering. Onl y at higher concentrations was overall breathing frequency decreased. There fore, at moderate concentrations of baclofen continuous ventilation replace d episodic ventilation, suggesting that a GABAB receptor-dependent pathway may regulate the clustering of lung breaths. (C) 2000 Elsevier Science Irel and Ltd. All rights reserved.