Neuroleptic-like properties of cholecystokinin analogs: distinctive mechanisms underlying similar behavioral profiles depending on the route of administration |
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Authors: | P De Witte M Gewiss B Roques J J Vanderhaeghen |
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Institution: | Laboratorie de Psychobiologie, Université de Louvain, Louvain-la-Neuve, Belgique. |
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Abstract: | Rats were trained to discriminate vehicle injections from intraperitoneal injections of 3 micrograms/kg caerulein, a cholecystokinin (CCK) neuropeptide analog. The reward that reinforced correct choices was an electrical brain stimulation self-administered by bar pressing. Dose-response quantitative generalization was obtained by using 1 and 2 micrograms/kg caerulein. Qualitative generalization to the vehicle occurred after injecting 10, 20 and 200 micrograms/kg unsulfated CCK-8, 10, 20 and 200 micrograms/kg CCK-4, 5 micrograms/kg CCK-8 and 1 microgram/kg caerulein, neurotensin or bombesin and 200 micrograms/kg apomorphine or 320 micrograms/kg amphetamine. Total generalization to the caerulein cue was obtained with 20 micrograms/kg sulfated CCK-8 or gastrin 2-17, 25 micrograms/kg somatostatin, 50 micrograms/kg haloperidol and 2 mg/kg chlorpromazine. The previous 5 mg/kg injection of an antiemetic drug such as chlorhydrate of trimethobenzamide did not eliminate the discriminative properties of a subsequent injection of caerulein. Our data thus tend to show that IP injection of caerulein produces effects similar to those of IP neuroleptics. |
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