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.