LESIONS OF REGIONS FOR IN-VITRO VENTILATORY GENESIS ELIMINATE GASPINGBUT NOT EUPNEA

Medullary regions, termed 'pre-inspiratory' and 'pre-Botzinger', are c onsidered critical for the neurogenesis of rhythmic ventilatory activi ty of in vitro preparations of the neonatal rat. We examined the influ ence of destruction of neurons in these regions, by microinjections of kainic acid, upon eupnea and gasping in vivo. Decerebrate, vagotomize d, paralyzed and ventilated rats of age 8-15 days were used; the phren ic nerve activity was recorded. Eupnea was not consistently altered fo llowing destruction of neurons in any region. However, in the majority of animals, anoxia-induced gasping was not observed following injecti ons of kainic acid into the 'pre-inspiratory' region, 'pre-Botzinger' complex or lateral tegmental field; the latter region is important for the neurogenesis of gasping in adults. Injections into other regions did not prevent the elicitation of gasping. These results do not suppo rt the possibility thar neuronal activities which are responsible for respiratory rhythm generation in vitro underlie the neurogenesis of eu pnea in vivo. (C) 1997 Elsevier Science B.V.