PLASMA CHOLECYSTOKININ CONCENTRATIONS IN 3-DAY-OLD LAMBS - EFFECT OF THE DURATION OF FASTING PRECEDING A SUCKING BOUT

Cholecystokinin (CCK) is a regulatory peptide released into the circul ation after the ingestion of food. Our knowledge concerning the factor s affecting its pattern of secretion in the mammalian neonate is scant y. Therefore, in this work we studied plasma concentrations of CCK in 3-day-old lambs after a sucking bout that followed either a short (2 h ) or a long fasting period (9 h). Plasma concentrations of CCK were me asured by radioimmunoassay in blood samples collected from jugular Vei ns 10 min before, immediately after a sucking bout, and then at 10-min intervals during the following hour. In the first experiment a period of fasting of 2 h before allowing the lambs to suck did not lower the levels of CCK. On the other hand, a significant decrease was recorded 10 min after feeding ended. Between 20 and 50 min after the end of su cking, the mean CCK concentration rose back to the pre-feeding level b efore decreasing again at 60 min. In the second experiment a period of fasting of 9 h, on the other hand, significantly lowered the levels o f CCK. Plasma levels also tended to decrease immediately after sucking was ended. This was followed by a substantial rise and levels remaine d high during the rest of the sampling period. It was concluded that t he decrease recorded immediately after a sucking bout could be due to an inhibitory effect of the oral phase while the following rise reflec ted the stimulatory effect of milk nutrients on intestinal CCK-produci ng cells.