Modelling the anxiety-depression continuum in chicks.

The clinical syndromes of anxiety and depression are now thought to exist along a temporal continuum and this construct has been modelled in a preclinical setting in chicks separated from conspecifics. This research sought to further the validity of the chick anxiety-depression continuum model. Dose-response studies using two classes of anxiolytics (chlordiazepoxide: 2.5, 5.0, 10.0, 15.0 mg/kg, and clonidine: 0.1, 0.15, 0.2, 0.25 mg/kg) and three classes of antidepressants (imipramine: 1.0, 3.0, 10.0, 15.0 mg/kg, maprotoline: 2.5, 5.0, 10.0, 20.0 mg/kg and fluoxetine: 1.0, 5.0, 10.0, 20.0 mg/kg) showed an ability to detect anxiolytic activity of chlordiazepoxide, clonidine, imipramine and maprotoline in the anxiety-like phase of the model and to detect antidepressant effects of imipramine, maprotoline and fluoxetine in the depression-like phase of the model. In addition, blood plasma interleukin-6, a biomarker of stress, was found to be elevated in response to social-separation stress. Collectively, these findings further characterize the model as a simulation of the anxiety-depression continuum and begin to establish the paradigm as a high-utility adjuvant to rodent screening assays for putative anxiolytic and antidepressant compounds.