FUNCTIONAL RELEVANCE OF ANAEROBIC METABOLISM IN THE ISOLATED RESPIRATORY NETWORK OF NEWBORN RATS

Respiratory (C-3-C-5) activity and extracellular K+, pH and Ca2+ (aK(e ), pH(e), [Ca](e), respectively) in the ventral respiratory group (VRG ) were measured in vitro. In brainstem-spinal cord preparations from 0 - to 1-day-old rats, lowering of bath glucose content from 30 to 10 mM for 1 h did not affect aK(e) or rhythmic activity. In preparations fr om 2- to 3-day-old animals, however, an aK(ee) rise by about 1 mM and disturbance of rhythm occurred after a delay of 50 min. Glucose-free s aline resulted, after about 30 min, in reversible blockade of respirat ory rhythm and an aK(e) rise by more than 8 mM, whereas pH(e) remained unaffected. Exposure to anoxia for 30 min after 1 h of pre-incubation in 10 mM glucose led to a progressive rise of aK(e), and a fall of [C a](e). The concomitant suppression of rhythm was irreversible in prepa rations from 2- to 3-day-old animals. Similar effects on aK(e) and [Ca ](e) and irreversible blockade of rhythm were revealed during anoxia i n glucose-free solution, or by addition of 2-5 mM iodoacetate to oxyge nated or hypoxic solutions. Iodoacetate led to a slow increase of pH(e ) by more than 0.2 pH units, which was accelerated by anoxia. Our find ings show that normal respiratory network functions in the en bloc med ulla, in particular from rats older than 1 day, depend on high bath gl ucose levels, necessary for effective utilization of anaerobic metabol ism.