engleski

Marble burying behaviour: comparison of mice and rats

Marble burying (MB) is a rodent model for obsessive-compulsive disorder in humans. It has been used by neuropharmacologists for decades to test potential anxiolytic drugs. MB is simple to perform, economical and practical for use. Finally, it is very thankful for Ethics Review of experiments involving laboratory animals (usually is awarded with the lowest severity score). MB is based on compulsive digging behaviour, which is natural for both, mice and rats. Interestingly, mice were much more frequently used in MB test than rats. Therefore, we present here the results of comparison of marble burying behaviour in two strains of mice (DBA2 and BalbC), Wistar rats and sublines of Wistar– Zagreb 5HT (WZ-5HT) rats, a genetic model of rats with constitutionally upregulated and downregulated serotonin (5HT) homeostasis. High-5HT and low-5HT subline of this model were developed by selective breeding for the extremes of platelet 5HT parameters. Thirty-three male rats (9 Wistar, 12 high-5HT and 12 low-5HT rats) and 40 male mice (18 BalbC, 22 DBA2) were used. Animals were individually exposed to glass marbles (15 mm diameter for mice and 24 mm for rats) for 30 minutes in standard cages fielded with 5 cm deep layer of saw dust. Total number of marbles distributed on the surface of bedding material was 12 for mice (in arrangement 4x3) and 8 for rats (4 marbles along 2 short walls of test cage). Number of marbles buried in sawdust is counted at the end of test. Marble is considered as buried if half or more of its volume is covered by sawdust. There was no difference in average percent of total marbles buried or average number of marbles buried between BalbC (71, 2% and 8.0) and DBA2 mice (69, 4% and 8.3). Wistar rats and rats from the high-5HT subline also buried similar average percent (85, 4% and 78, 6% of total marbles buried, respectively) and similar average number of marbles (6, 8 and 6, 3 marbles, respectively). But, the number of marbles and percent of total marbles buried by rats from the low-5HT subline was more than twice lower than those estimated for Wistar or high-5HT subline (30, 2% versus 85, 4% and 78, 6% of total marbles). These differences reached statistical significance (one way ANOVA, F=21.37, p= 0, 0001 ; Tukey multiple comparison test, p= 0, 001 high-5HT vs low-5HT subline and Wistar vs low- 5HT subline). In conclusion, no difference has been found in compulsive digging behaviour between two strains of mice known as relatively anxious in different anxiety models. But, high- 5HT subline of WZ-5HT model and standard Wistar rats express significantly more compulsive digging than low-5HT rats. Therefore, results indicate a relationship between increased endogenous 5HT tone and anxiety. They also suggest that animals from the high-5HT (hyperserotonergic) subline may be a better model for testing anticompulsive drugs than low- 5HT (hyposerotonergic) animals.

Marble burying ; DBA2 and BalbC mice ; Wistar rats ; Wistar-Zagreb 5HT rats

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