Rationale: Little is known about the structural characteristics of the behavior of rats with enhanced anxiety level. To fill this gap, a study was undertaken where effects of an anxiogenic drug were examined on behavioral structure of rats tested in hole board.
Objectives: This study investigates effects of increased anxiety level on the structure of the behavior of rats tested in hole board METHODS: Different doses of FG7142 (1, 4, 8 mg/kg IP), a potent anxiety-inducing drug, were administered to three groups of male Wistar rats. A further group was administered saline. Experiments were recorded through a digital camera. Quantitative and multivariate approaches were applied.
Results: Percent distributions and durations showed increases of immobile sniffing, rearing, head dip, and edge sniff and a significant reduction of grooming activities and of walking. In addition, a decrease of head dip/edge sniff ratio was detected. Transition matrices evidenced that FG7142 provoked evident modifications of behavioral structure mainly of general exploration of environment and focused exploration of the hole. Finally, adjusted residuals showed a reduced effectiveness of FG7142 on transitions from head dip to edge sniff; on the contrary, transitions from edge sniff to head dip underwent evident dose-dependent changes.
Conclusions: Present study provides a useful tool to analyze behavioral responses to different anxiety conditions. Accordingly, it is demonstrated that a condition of increased anxiety deeply modifies the structure of male Wistar rat's behavior in hole board. In addition, our results suggest that evaluation of head dip/edge sniff ratio can be considered a reliable index to appraise effects of pharmacological manipulation of anxiety and related behavioral elements.
Keywords: Adjusted residuals; Anxiety; Cluster analysis; Edge sniff; FG7142; Head dip; Hole board; Wistar rat.