An alternative explanation for apparent satiating properties of peripherally administered bombesin and cholecystokinin in domestic fowls.
This paper describes a series of experiments with domestic fowls designed to investigate different effects of peripherally administered bombesin (BBS) and cholecystokinin octapeptide (CCK8), with a view to gaining a better understanding of their proposed roles as physiological satiety signals. Following intravenous injections of 1-10 micrograms/kg BBS or CCK8, short periods of complete inhibition of feeding coincided with periods of abnormal gizzard motility, and longer periods of reduced feeding were associated with periods of abnormal gastrointestinal (GI) motility. Increases in heart rate, measured in a separate experiment, coincided with the periods of altered GI and feeding activities. Effects of the peptides on GI motility and feeding were strongly related to dose with CCK8, but not with BBS, and effects of (2 micrograms/kg) BBS and CCK8 on feeding were additive. Evidence from conditioned avoidance tests suggested that consequences of (10 micrograms/kg) BBS and CCK8 injections may be mildly aversive, perhaps more so with BBS, and in another experiment inhibition of feeding by (8 micrograms/kg) BBS (but not CCK8) was almost abolished in birds tranquillised with a reserpine derivative drug. CCK8 was more potent than BBS at suppressing feeding only when relatively high doses (8 and 10 micrograms/kg) were injected. It is suggested that peripherally administered BBS and CCK8 may act on feeding in similar ways, with animals being distracted by possible abdominal discomfort associated with the abnormal GI responses. The results indicate that immediate discomfort may be more severe with BBS, but that discomfort associated with CCK8 may last longer. It is further suggested that satiating properties of the peptides are less apparent in situations where animals are less easily distracted by discomfort, when their arousal is reduced, when their perception of discomfort is reduced and when their motivation to feed is increased.
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001839:Bombesin / Q000494:pharmacology*; D002766:Cholecystokinin / Q000494:pharmacology*; D003213:Conditioning, Psychological / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004435:Eating / Q000187:drug effects; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D011200:Poultry / Q000502:physiology*; D012527:Satiation / Q000187:drug effects*; D012528:Satiety Response / Q000187:drug effects*; D014149:Tranquilizing Agents / Q000494:pharmacology
D004338:Drug Combinations; D014149:Tranquilizing Agents; D002766:Cholecystokinin; D001839:Bombesin