[Analysis of the excitatory effects of dimefline on respiration in rabbits].

The present study was undertaken to analyse the mechanisms of the excitatoryeffect of dimefline(DIM)on respiration in 29 locally anesthetized and paralyzedrabbits by means of electrophysiological methods.In 20 intact animals,DIMgiven intravenously(0.05—0.3mg/kg)enhanced the phrenic discharges.Thesimilar effects were observed in decerebrate animals.Under the state of apneusticor gasping breathing after transection of the brainstem,DIM also increased thephrenic discharges and respiratory frequency.The effects of DIM,GABA and BIC(bicuculline)given iontophoretically on60 units in NTS area of medulla were observed in 11 intact animals.In 36 GABA-sensitive units(27 inspiratory related units;9 non-respiratory related units),DIMblocked the GABA-induced depression on unit discharges in 32 and had no effectson the rest.DIM given intravenously produced excitatory effect and antagonizedinhibitory effect of GABA in 13 units which were affected also by iontophoreticapplication of DIM.The results indicate that the excitatory effect of DIM on respiration may be theresults of blocking the inhibitory effect of intrinsic GABA on respiratory and non-respiratory units in respiratory center of the brainstem.