Dose-dependent interaction between cholecystokinin and sham feeding.
Previous work in this laboratory indicated that decreases in feeding motivation produced by cholecystokinin octapeptide (CCK-8) develop through synergism with signals generated by feeding. In these experiments, we used a runway paradigm to assess the contribution of signals from the oral cavity to this interaction. In contrast to the substantial (44%) impairment in runway performance produced by the combination of 1 microgram/kg CCK-8 and 5 min normal prefeeding, 5 min sham feeding failed to potentiate the effect of 1 microgram/kg CCK-8. Sham feeding in conjunction with this dose of CCK-8 reduced running speed by no more (2%) than CCK-8 alone (9%). Similar results were obtained whether rats were allowed a longer sham feeding interval (12 min) or the prefeeding interval was shifted in time so that it ended only 3 min before the start of the runway test. By contrast, larger doses of CCK-8 interacted with 5 min sham feeding to substantially impair runway performance; significant decreases in speed of 29% and 41% were observed after 2 and 4 micrograms/kg CCK-8, respectively. Results with these doses indicate that synergy between CCK-8 and signals from the oral cavity can contribute to the inhibitory effects of this agent. However, the failure of the combination of the 1 microgram/kg dose and sham feeding to replicate the interaction seen with normal prefeeding indicates the additional involvement of signals arising from food stimulation distal to the oropharynx.
Department of Psychology, University of Alabama, Birmingham 35294.
J E
JE
Cox
M J
MJ
Smith
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004435:Eating; D008297:Male; D009042:Motivation / Q000187:drug effects / Q000502:physiology; D009055:Mouth / Q000502:physiology; D010614:Pharynx / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000494:pharmacology*
D012844:Sincalide