Different targets involved in the effect of cholecystokinin on respiration

Respiratory and cardiovascular effects of intravenous administration of cholecystokinin octapeptide (CCK-8) (0.3 to 20 micrograms/kg) were compared in different cat preparations: chronically implanted and decerebrate vagotomized or decerebrate non-vagotomized. In all preparations CCK-8 induced an immediate drop in blood pressure (between 44.0 and 58.1%) and heart rate (between 25.1 and 62.5%) which had completely recovered 5 min after the end of the injection. During cardiovascular modifications tidal volume decreased in non-vagotomized cats and was associated with a decrease in respiratory frequency in decerebrate cats and with an increase in respiratory frequency in chronically implanted animals. Only an increase of tidal volume occurred in vagotomized cats. After cardiovascular conditions had returned to normal, tidal volume remained significantly modified: decreased in chronically implanted (-39%), in decerebrate non-vagotomized (-34%) and increased in vagotomized cats (+27.7%). However, modifications of frequency persisted only in chronically implanted preparations (+69.2%). Recovery from respiratory modifications occurred 30 min after injection. These effects were not produced by systemic administration of non-sulfated CCK-8. The cardiorespiratory modifications induced by CCK-8 are discussed in relation to the different targets which can be reached by the octapeptide in each preparation.