Modulation of memory, reinforcement and anxiety parameters by intra-amygdala injection of cholecystokinin-fragments Boc-CCK-4 and CCK-8s.
This series of experiments examined the effects of the cholecystokinin (CCK) fragments Boc-CCK-4 and CCK-8s on memory, reinforcement and anxiety following unilateral injection into the central nucleus of the amygdala (CeA). In experiment 1, rats with chronically implanted cannulae were injected with CCK-8s or Boc-CCK-4 and were tested on a one-trial uphill avoidance task. Post-trial injection of 20 ng Boc-CCK-4 or 1 ng CCK-8s was found to improve the retention performance, whereas lower and higher doses had no effect. The hypermnestic effects of Boc-CCK-4 and CCK-8s were no longer evident when injection was performed 5 h, rather than immediately, after the learning trial. In experiment 2, the elevated plus-maze was used to gauge anxiogenous properties of intra-amygdala injections of Boc-CCK-4 and CCK-8s in memory-enhancing doses. The treatment with 20 ng Boc-CCK-4 and 1 ng CCK-8s did not influence the number of entries into and time spent on the open and enclosed arms of the maze as well as other anxiety-related behaviors. In experiment 3, possible reinforcing effects of the CCK-fragments were examined. After intra-amygdala injection of Boc-CCK-4 or CCK-8s in memory-enhancing doses the rats were placed into one of four restricted quadrants of a circular open field (closed corral) for a single conditioning trial. Subsequent tests for conditioned corral preference revealed no evidence for reinforcing or aversive effects of the CCK-fragments. In sum, these findings indicate that Boc-CCK-4 and CCK-8s facilitate memory processing upon injection into the CeA without exerting reinforcing or anxiogenous effects.
Huston
J P
JP
Institute of Physiological Psychology, Heinrich-Heine-University of Düsseldorf, Germany.
Schildein
S
S
Gerhardt
P
P
Privou
C
C
Fink
H
H
Hasenöhrl
R U
RU
D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001007:Anxiety; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects; D003213:Conditioning, Psychological; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012054:Reinforcement, Psychology; D012844:Sincalide / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D013758:Tetragastrin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
C090019:8-sulfocholecystokinin octapeptide; D013758:Tetragastrin; C063051:butyloxycarbonyl-tryptophyl-methionyl-aspartyl-phenylalaninamide; D012844:Sincalide