[Role of pneumotaxic centers in regulating the length of inspiration in decerebrate cats].

Off-switch of pneumotaxic centers (PTC) as well as vagotomy evoked an increment in tidal volume (VT) and inspiratory duration (TI) in quiet breathing. Increase of TI is more pronounced after off-switch of PTC. In such cats lung ventilation is diminished in result of decrease in sensitivity to chemoceptive stimuli. With increment of VT evoked by rebreathing after hyperventilatory apnoae TI at first were increased. Inspirations become apneustic with weak dependence on VT (diapason I). Then TI quickly diminished, inverse relationship between VT and TI was preserved (diapason II). TI reached its minimal values (diapason III). Inspiratory off-switch threshold and minimal TI were more increased after PTC lesion than after vagotomy. PTC and lung stretch receptors affected relationship between VT and TI synonymously, but PTC had a relatively greater importance in its determining.