BEHAVIORAL AND PHARMACOLOGICAL CHARACTERIZATION OF THE CANOPY STRETCHED ATTEND POSTURE TEST AS A MODEL OF ANXIETY IN MICE AND RATS

The behavioural element, stretched attend posture (SAP), is an importa nt component of the ''risk-assessment'' repertoire of defensive behavi our in rodents. The present experimental paradigm was devised as a nov el and simple method of eliciting high levels of SAP in mice and rats. The SAP test apparatus comprised an elevated black Perspex circular p latform. A smaller clear red Perspex circular ''Canopy'' was supported directly above the platform by a central pillar, thus dividing the pl atform into an inner, dimly lit covered zone and an outer, brightly li t exposed zone. In both the rat and mouse version of this model, vehic le-treated animals exhibited a marked preference for exploring the cov ered zone and also exhibited high baseline levels of SAP, particularly at the covered zone boundary whilst they investigated the exposed zon e. In the mouse SAP test, the benzodiazepine receptor agonists, diazep am (0.5 mg/kg SC) and chlordiazepoxide (2 mg/kg SC), and the 5-HT1A re ceptor agonists, buspirone (1 and 3 mg/kg SC), ipsapirone (3 mg/kg SC) and 8-OH-DPAT (0.2 mg/kg SC), all significantly decreased the frequen cy of SAP without impairing motor activity. In the rat SAP test, diaze pam (0.5 mg/kg SC) significantly decreased, whilst the anxiogenic 5-HT 2C/1B receptor agonist, mCPP (0.25 and 0.5 mg/kg SC), significantly in creased, the frequency of SAP. Ipsapirone (3 mg/kg SC) induced a non-s pecific behavioural inhibition. These data suggest that the ''Canopy'' SAP test is a useful paradigm to investigate risk assessment behaviou r in both rats and mice, and may provide a sensitive novel rodent mode l of anxiety.