Structure of rat behavior in hole-board: I) multivariate analysis of response to anxiety.

Aim of present paper was to carry out an analysis of rat behavior in hole-board following different multivariate approaches. Thirty male Wistar rats were observed in a hole-board apparatus and their behavior recorded for 10 min through a digital videocamera for a following frame-by-frame analysis. Both descriptive and multivariate analyses were used. Descriptive analysis showed that roughly 85% of the whole behavioral structure encompassed six patterns appearing during the first minute of observation: walking, climbing, rearing, immobile-sniffing, edge-sniff and head-dip. As to multivariate approach, cluster analysis showed three main dyadic associations: [edge-sniff/head-dip], [walking/climbing], [face-grooming/body-grooming]. Path diagram, obtained on the basis of relative frequencies of transitions among behavioral patterns (stochastic analysis), emphasized cluster analysis results. Adjusted residuals confirmed, from a statistical point of view, the strong relationships among specific patterns. Results demonstrate that immobile-sniffing has a crucial role in rat behavioral organization and head-dip is closely related with edge-sniff which is suggested to be a specific sniffing activity of holes edge never properly considered. Present research shows that multivariate approaches, revealing patterning among different behavioral elements in hole-board, could improve test reliability, providing a more useful tool to investigate behavioral effects of anxiolytic drugs.