Effects of PGI2 on pattern of breathing in the pig during aortic obstruction

We studied the effects of prostacyclin on pattern of breathing in six anaesthetized pigs with aortic obstruction. PGI₂ causes a rightward displacement of VT/T relationship (Hering-Breuer threshold curve) without a corresponding change I respiratory flow. With airways occluded at the end expiratory level, we analyzed how PGI affects the central respiratory rhythm in the absence of the phasic lung volumi-related vagal loop. Infusion of prostacyclin causes leftward displacement of the T /T relationship and an increase in T o correlated with the hypotensive action The change in the bulbo-pontine pacemaker is caused by a marked increase in T , and this suggests that PGI can modulate the central respiratory rhythm, inde$endently of the blood pressure level.