The importance of acclimatisation and habituation to experimental conditions when investigating the anorectic effects of gastrointestinal hormones in the rat

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Abstract
Peptide YY3-36 (PYY3–36), glucagon-like peptide-1 (GLP-1), oxyntomodulin and cholecystokinin (CCK) are gastrointestinal-derived hormones that are released postprandially in proportion to the amount of calories ingested. All significantly reduce food intake following peripheral administration to rodents. We have investigated the effect of handling, exposure to a novel environment or to environmental enrichment on the anorectic effect of these gut hormones. Results suggest that the transfer of a rat into a novel environment (cage change) inhibits the anorectic response to peripherally administered PYY3–36 and oxyntomodulin (1 h food intake reduction (% saline control): PYY/home cage 82.3±5.9%, PPPPPPP3–36 is attenuated in unhandled rats (88±4.2% saline control, P=ns) or rats exposed to environmental enrichment (103.3±9.7% saline control, P=ns), but not in animals that were handled extensively prior to the study (80.1±7.3% saline control, P<0.05). These studies highlight the importance of handling, acclimatisation and habituation of rodents to experimental conditions prior to investigating the ability of gut hormones to alter food intake.