title: Role of hypotension induced by PGI2 on the control of depth and frequency of breathing.
abstract: We studied the respiratory response to infusion of prostacyclin (PGI2) in 7 anaesthetized pigs in an attempt to understand whether the changes in pattern of breathing were due to a direct action of the substance or to the concomitant hypotensive effect. The depth and frequency of breathing were analyzed in terms of the threshold-inhibition curve for termination of inspiration (VT/TI relationship) and of bulbo-pontine rhythm, estimated from inspiratory and expiratory time during occlusion of the airways at the end expiratory level (TE/TI relationship). This provide the central respiratory rhythm when the phasic lung volume receives no input from pulmonary stretch receptors. The hypotension induced by PGI2 increased pulmonary ventilation mainly through a change in VT and caused a slight rightward displacement of VT/TI relationship without modifying the slope of the curve. This effect seems to be vagally mediated. PGI2 also changed the bulbo-pontine rhythm. Our results show that PGI2 modifies the vagal discharge and bulbo-pontine rhythm by two opposite mechanisms: hypotension and an apparent direct action on carotid and aortic baroreceptors.
mesh_terms: D000818:Animals; D011464:Epoprostenol / Q000494:pharmacology*; D005260:Female; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D011453:Prostaglandins / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects*; D013552:Swine; D013562:Sympathectomy; D014628:Vagotomy
chemical_list: D011453:Prostaglandins; D011464:Epoprostenol