Pharmacological analysis of the regulation of the phase duration of the respiratory cycle

: The oxotremorine, arecoline, physostigmine, armine, hyoscine and amphetamine affected the inspiratory (Ti) and expiratory (Te) duration as well as the Ti/(Ti + Te) ratio in 20 anesthetized cats. M-cholinopositive agents decreased the Ti/(Ti + Te) ratio due to shortening of inspiratory duration and simultaneous lengthening of expiratory one. Changes in the blood pressure and Ti/(Ti + Te) patterns appeared to be similar. The difference between our data and the data obtained by means of iontophoretic application of the agents to identified respiratory neurons might be accounted for by the fact that the routine technique used to identify respiratory neurons was unreliable.