INSPIRATORY TIMING REGULATION OF PGF2-ALPHA IN NEWBORN PIGS

In intact and vagotomized anesthetized, spontaneously breathing piglets, we investigated the regulation of inspiratory timing evoked by i.v. administration of prostaglandin (PG) F2alpha. The inspiratory time was evaluated from the now trace as an index of mechanical inspiratory time (Ti) and from costal and crural diaphragmatic EMG (Ti(EMG)) as an index of neural inspiratory time. Our results under control conditions showed that Ti(EMG) was shorter than Ti. Vagotomy abolished the difference, inducing a change in the power spectrum without modifying the centroid frequency (Cf). PGF2alpha lenghthened Ti(EMG), causing a postinspiratory diaphragmatic discharge to appear, while mechanical inspiratory time decreased significantly. Postvagotomy i.v. administration of PGF2alpha did not cause any significant changes in inspiratory time and did not evoke the postinspiratory discharge. The i.v. administration of PGF2alpha before and after vagotomy did not change the centroid frequency in spite of recruitment of new motor units synchronized with those that are active under control conditions.