Anxiety-related behaviour of low brain angiotensinogen transgenic rats in the canopy test.

This study investigated risk assessment and anxiolytic/anxiogenic drug effects in "low brain angiotensinogen" transgenic rats (TGR) in comparison to wild-type Sprague-Dawley rats (SD) in the canopy test of anxiety-related behaviour. TGR showed a higher frequency of the risk assessment behaviour as indicated by performance of stretched attend posture (SAP) compared to SD. Diazepam (0.25mg/kg) reduced SAP in both strains, whereas FG-7142 had no significant effect. The 5-HT(1B/2C) agonist mCPP (0.5-2mg/kg) reduced SAP in both strains. Diazepam (0.25-1mg/kg) increased head dips and decreased the time spent under the canopy in SD rats. There were significant anxiogenic effects of both FG-7142 (3-6 mg/kg) and mCPP (0.5-2mg/kg) on these parameters for SD but not TGR. Diazepam (1mg/kg) increased the number of entries into the open zone in both strains. mCPP reduced this parameter in SD (2mg/kg) and TGR (0.5-2mg/kg). FG-7142 had a similar effect in SD (3-6 mg/kg) and TGR (6 mg/kg). This study showed a significant transgenic effect on SAP. The increased number of SAP seen in TGR could be reduced with diazepam. Although both FG-7142 and mCPP are generally anxiogenic, no significant effects of FG-7142 on SAP were observed and mCPP even reduced SAP.