Anticholinergic drugs and open-field behavior in chickens

A critical review of fear tests used on cattle, pigs, sheep, poultry and horses

Fear is arguably the most commonly investigated emotion in domestic animals. In the current review we attempt to establish the level of repeatability and validity found for fear tests used on cattle, pigs, sheep and goats, poultry and horses. We focus the review on the three most common types of fear tests: the arena test (open field), the novel object test, and the restraint test. For some tests, e.g. tonic immobility in poultry, there is a good and broad literature on factors that affect the outcome of the test, the validity of the test and its age dependency. However, there are comparatively few of these well defined and validated tests and what is especially missing for most tests is information on the robustness, i.e., what aspects can be changed without affecting the validity of the tests. The relative absence of standardized tests hampers the development of applied ethology as a science.

Anxiogenic effects of a beta-carboline on tonic immobility and open field behavior in chickens (Gallus gallus)

Tonic immobility (TI) is an innate form of active motor inhibition displayed by many species in response to restraint. It is strongly influenced by manipulations that affect fear, and is thought to be the last in a series of responses to attack by a predator. The suggestion that GABA systems may be involved in TI was investigated by assessing the effects of the alpha-GABAA inverse agonist beta-CCM (beta-carboline-3-carboxylic acid-N-methylamide), which is thought to have anxiogenic properties, on the immobility response and open field behavior in chickens (Gallus gallus). Birds given beta-CCM displayed longer durations of TI than those given control injections. Although there was a tendency towards increased susceptibility in the groups given the drug, it was not significant. In the open field test, the drug reduced activity and vocalization relative to control levels. The results are discussed in terms of the involvement of GABA systems in TI and related behaviors, and the suggestion that alpha-GABAA inverse agonists are anxiogenic agents.