Effects of Different Anxiety Levels on the Behavioral Patternings Investigated through T-pattern Analysis in Wistar Rats Tested in the Hole-Board Apparatus

Abstract

The Hole-Board is an ethologically based tool for investigating the anxiety-related behavior of rats following manipulation of the central anxiety level. The present paper aims to assess behavioral patterning following pharmacological manipulation of emotional assets in Wistar rats tested in this experimental apparatus. For this purpose, the behavior of three groups of rats injected with saline, diazepam or FG7142 was evaluated using conventional quantitative and multivariate T-pattern analyses. The results demonstrate that quantitative analyses of individual components of the behavior, disjointed from the comprehensive behavioral structure, are of narrow utility in the understanding of the subject’s emotional condition. Among the components of the behavioral repertoire in rodents tested in the Hole-Board, Edge-Sniff and Head-Dip represent the most significant ones to rate anxiety level. They are characterized by a strong bivariate relationship and are also firmly part of the behavioral architecture, as revealed by the T-pattern analysis (TPA), a multivariate technique able to detect significant relationships among behavioral events over time. Edge-Sniff → Head-Dip sequences, in particular, are greatly influenced by the level of anxiety: barely detectable in control animals, they completely disappear in subjects with a reduced level of anxiety and are present in almost 25% of the total of T-patterns detected in subjects whose anxiety level increased.

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“…Interestingly, GAERS treated with vehicle showed a higher frequency of Head-Dip ( p < 0.05), Face Grooming ( p < 0.05), Body Grooming ( p < 0.05), Head-Dip/Edge-Sniff ratio ( p < 0.05), and a decreased immobility ( p < 0.01) than vehicle-treated NEC ( Figure 2 ). Thus, since the ratio of Head-Dip/Edge-Sniff is an indication of the difference of the anxiety status between different animal groups ( Casarrubea et al, 2017 , 2021b ), these results further indicate that GAERS treated with vehicle are less anxious than NEC rats.…”

“…Finally, the percent distributions of T-patterns encompassing behavioral components of hole-exploration predictive of the animal anxiety level ( Casarrubea et al, 2021b ) are illustrated in Figure 7 . Chi-square test revealed significant ( p < 0.05) differences between vehicle-treated GAERS and vehicle-treated NEC, WIN 55,212-2-treated NEC, and vehicle-treated NEC, both for T-patterns encompassing Head-Dip ( Figure 7A ) and Edge-Sniff ( Figure 7B ), but no significant differences between vehicle- and WIN 55,212-2-treated GAERS in both parameters ( Figures 7A,B ).…”

“…The reduced anxiety-like phenotype with neophilic responses observed in vehicle-treated GAERS compared to NEC is consistent with the mixed quantitative-qualitative analysis of the T-patterns detected. Indeed, vehicle-treated NEC rats had a much lower number and less complex T-pattern sequences compared to vehicle-treated GAERS, a condition that has been related to a lower anxious status ( Casarrubea et al, 2021b ). Notably, vehicle-treated NEC rat’s structural behavioral analysis did not show any T-patterns containing head-dips and only a few containing edge-sniffs.…”

“…On the other hand, in GAERS rats treated with the vehicle, the T-pattern variability was greater as was its complexity and shows T-patterns containing Head-Dips. GAERS rats, therefore, are motivated to explore more by implementing more complex and articulated strategies, in line with lower anxiety levels compared to vehicle-treated NEC ( Casarrubea et al, 2021b ).…”

“…To untangle CB1R-induced hypomotility ( Zimmer et al, 1999 ) from any anxiety-like behavior effect, we used Temporal -pattern (T-pattern) detection and their multivariate analysis that has been shown to reveal hidden behavioral components and distinguish between different anxiety levels ( Casarrubea et al, 2018 , 2021b ; Aiello et al, 2020 ). Unexpectedly, in vehicle-treated GAERS, a lower anxious state and reduced immobility were observed than in vehicle-treated NEC rats.…”