Modeling anxiety-like states: pharmacological characterization of the chick separation stress paradigm.

While previous research has sought to validate the chick separation stress paradigm as an anxiolytic screening assay, it is unknown whether the paradigm better models a nonspecific anxiety-like state or something similar to panic disorder or generalized anxiety disorder. To characterize the anxiety model pharmacologically, cockerels were administered drug probes that were either: (1) only effective for treating panic disorder (phenelzine 3.125-25.0 mg/kg), (2) effective for treating both panic disorder and generalized anxiety disorder (alprazolam 0.065-0.5 mg/kg; clonidine 0.1-0.25 mg/kg; imipramine 1.0-15.0 mg/kg), (3) only effective for treating generalized anxiety disorder (buspirone 2.5-10.0 mg/kg; trazodone 0.1-3.0 mg/kg) or (4) capable of exacerbating symptoms of panic disorder in humans (yohimbine 0.1-3.0 mg/kg). At 7 days after hatch, chicks received either vehicle or drug probe intramuscularly 15 min prior to social separation under a mirror (low-stress) or no-mirror (high-stress) condition for a 180-s observation period. Dependent measures were distress vocalizations to index separation stress and sleep-onset latency to index sedation. Phenelzine, alprazolam, imipramine and clonidine were able to attenuate distress vocalizations (at doses without significant sedation) whereas buspirone and trazodone did not. Paradoxically, yohimbine modestly attenuated distress vocalizations. These results suggest that the chick separation stress paradigm better models panic disorder than generalized anxiety disorder as an anxiolytic screen.