Development of the respiratory response to hypoxia in the isolated brainstem of the bullfrogRana catesbeiana

• DOI: 10.1242/jeb.01399
• Publication Date: 2005-01-05T18:55:02Z
• Authors: Rachel E. Winmill; Anna K. Chen; Michael S. Hedrick
• Keywords: Hypoxia

The aim of this study was to examine the effects cellular hypoxia, and contribution anaerobic metabolism, on respiratory activity in bullfrogs at different stages development. Respiratory-related neural recorded from cranial nerve rootlets isolated brainstem preparations pre-metamorphic (Taylor-Kollros (T-K) VIII-XVI) postmetamorphic tadpoles (T-K XXIV-XXV) adults. Changes fictive gill/lung brainstems lung adults were examined during superfusion with control (98% O(2)/2% CO(2)) or hypoxic N(2)/2% artificial cerebrospinal fluid (aCSF). Iodoacetate (IAA; 100 micromol l(-1)) used conjunction aCSF inhibit glycolysis. Gill burst frequency did not change over a 3 h exposure hypoxia slowed significantly, but only after hypoxia. Blockade glycolysis IAA significantly reduced time could be maintained pre-metamorphic, adult, brainstems. In post-metamorphic adults, became more episodic within 5-15 min exposure, subsequently abolished every preparation. cessation breathing restored levels upon reoxygenation. Neither tadpole nor adult exhibited changes bursts resembling 'gasping' that is observed mammalian exposed severe There also significant increase 'non-respiratory' brainstems, These results indicate are capable maintaining for rely great extent metabolism maintain motor output. Upon metamorphosis, however, pattern, including increased episodes, non-ventilatory reversible activity. Adults have little no ability through but, instead, stop until oxygen available. This 'switch' response coincides morphologically loss gills obligate air-breathing frog. We hypothesize an adaptive, energy-saving low oxygen.