Minimized tolerance to the suppressive effects of CCK8 on operant responding.
This study was designed to determine if tolerance to cholecystokinin octapeptide (CCK8) could be prevented or minimized by spacing injections, and if an appetitive operant conditioning paradigm provides a sensitive baseline to test the effects of CCK8. Male Sprague-Dawley rats were trained to press a lever for water according to a fixed-interval 60-sec schedule of reinforcement. After response rate stabilized, rats were given a series of CCK8 (0.04 mg/kg, ip) injections spaced several days apart. The first injection of CCK8 produced complete response suppression during the 30-min test session, while later injections produced partial or complete suppression. Thus, tolerance to CCK8, as measured by operant response rate, may be minimized if injections are appropriately spaced.
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000494:pharmacology*
D012844:Sincalide