Injection timing determines whether intragastric ethanol produces conditioned place preference or aversion in mice

• Published in: Pharmacology, biochemistry and behavior Vol. 72; no. 3; pp. 659 - 668
• Main Authors: Cunningham, Christopher L, Clemans, Jessica M, Fidler, Tara L
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.2002; Elsevier Science
• Subjects: Alcoholism and acute alcohol poisoning; Animals; Aversion; Avoidance Learning - drug effects; Avoidance Learning - physiology; Biological and medical sciences; Conditioning (Psychology) - drug effects; Conditioning (Psychology) - physiology; DBA/2 inbred mice; Drug Administration Schedule; Ethanol - administration & dosage; Ethanol - blood; Intubation, Gastrointestinal; Locomotor activity; Male; Medical sciences; Mice; Mice, Inbred DBA; Motor Activity - drug effects; Motor Activity - physiology; Place conditioning; Preference; Sensitization; Toxicology; DBA/2 inbred mice; Place conditioning; Sensitization; Preference; Aversion; Locomotor activity; Ethanol; Conditioned place preference; Toxicity; Alcoholism; Rodentia; Instrumental conditioning; Learning; Intragastric administration; Locomotion; Vertebrata; Mammalia; Acquisition process; Mouse; Animal; Reward; Timing; Conditioned aversion
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/S0091-3057(02)00734-7

Previous studies have shown that mice develop conditioned place preference (CPP) when ethanol is administered by intraperitoneal (ip) or intravenous (iv) injection. The present studies examined CPP in mice using the intragastric (ig) route of administration. Inbred mice were surgically implanted with chronic intragastric cannulae and exposed to an unbiased place conditioning procedure in which infusion of ethanol (2 or 4 g/kg) was paired with a conditioned stimulus (CS+). A different CS was paired with water. In Experiments 1–2, ethanol was infused just before exposure to CS+. Contrary to previous studies involving intraperitoneal injection, infusion of 4 g/kg ig ethanol produced a significant conditioned place aversion (CPA). However, when a 5-min delay was inserted between infusion and CS exposure (Experiments 3–4), the same dose produced CPP. These outcomes are not consistent with expectations derived from a recent study in selectively bred rats, suggesting that sensitivity to ethanol reward is enhanced by intragastric administration. However, the finding that intragastric ethanol can produce either CPP or CPA depending on dose and injection timing is consistent with previous intraperitoneal ethanol studies in mice. Although the parameters differ for each route of administration, it appears that the same underlying processes can be invoked to explain how manipulation of injection timing affects the direction of ethanol-induced place conditioning. More specifically, in both cases, CPA can be attributed to an initial, short-lived aversive effect, whereas CPP can be attributed to a delayed rewarding effect of ethanol.