Lack of social touch alters anxiety-like and social behaviors in male mice

Figures & data

Figure 1. Mice spent half a day physically contacting each other. (A) A raster plot showing the physical interactions of pair-housed mice over 24 h. (B) The total time for specific interactions between two mice in the dark phase (Kruskal–Wallis followed by Dunn’s test, p values were determined by comparison to both moving-no contact). (C) The total time for specific interactions between two mice in the light phase (Kruskal–Wallis followed by Dunn’s test, p values were determined by comparison to no moving-contact). (D) The percentage of time for specific interactions between two mice in 24 hours. *p < 0.05, **p < 0.01, ***p < 0.001; n = 3 pairs; mean ± S.E.M.

(a) A raster plot of three pairs of mice suggests that the mice spent a significant amount of time in physical contact over 24 h. (b) In the dark phase, mice displayed mostly exploratory behaviors without direct contact (both moving–no contact). (c) In the light phase, mice mostly contacted each other without moving (no movement–contact). (d) A pie chart shows that mice spent more than half a day physically contacting each other.

Figure 2. Three different housing conditions and the experimental schedule. (A) Male mice were housed in three different conditions: pair-, split-, and single-housing conditions. (B) Schematic diagram of the experimental schedule.

(a) Male mice were housed in three different conditions: pair-, split-, and single-housing conditions. Mice in split-housed cages were separated by a transparent plate with holes to minimize physical contact. (b) After one month of housing in the different conditions, mice were tested in multiple behavioral assays in sequence with at least a 48-h interval between each assay.

Figure 3. Mice housed in divided cages showed increased anxiety-like behavior. (A) Representative traces of mice in the open field. (B) Travel distances in the open-field test. (C) Time spent in the inner zone in the open-field test. (D) Time spent in the light zone during the light-dark box test. (E) The number of transitions between the light and dark zones. Welch's ANOVA followed by Dunn’s test; *p < 0.05, **p < 0.01, ***p < 0.001; n = 12–14 per group; mean ± S.E.M.

(A) Representative traces of mice in the open field. (B) In the open field test, there was lower activity in the single-housed mice than in the split-housed mice. (C) In the open field test, split-housed mice spent significantly less time in the center zone than pair-housed and single-housed animals. (D) In the light-dark box test, split-housed mice spent significantly less time in the light chamber than pair-housed and single-housed animals. (E) The number of transitions between the two chambers in the light-dark box test were lower in the split-housed group than in the pair-housed group.

Figure 4. Depression-like behavior was similar among mice housed in different conditions. (A) Latency to the first bout of immobility in the forced swim test. (B) The total immobility time in the forced swim test. (C) Latency to the first bout of immobility in the tail suspension test. (D) The total immobility time in the tail suspension test. Welch's ANOVA followed by Dunn’s test; n = 12–14 per group; mean ± S.E.M.

(a) There was no difference among the three groups in forced swimming latency. (b) There was no difference among the three groups in forced swimming immobility. (c) There was no difference among the three groups in tail suspension latency. (d) There was no difference among the three groups in tail suspension immobility.

Figure 5. Mice housed in divided cages showed changes in social behaviors. (A) Social dominance evaluated by pairwise comparisons in the tube test (Wilcoxon signed-rank test, n = 10–12 pairs). (B) The total duration of social interaction in the intruder assay. (C) The latency to physical interaction in the intruder assay. Welch's ANOVA followed by Dunn’s test; *p < 0.05, **p < 0.01; n = 12–14 per group; mean ± S.E.M.

(a) Split-housed mice showed a higher wining rate (more dominant) than single-housed mice in the tube test. Split-housed mice also showed a higher trend of winning than pair-housed mice in the tube test (p = 0.0547). There was no difference between mice housed in paired- and single-housing conditions. (b) There was no difference among the three groups in the total duration of social interaction in the intruder assay. (c) Split-housed mice showed a shorter latency time to interact with intruders than single-housed mice.

Figure 6. Expression of the cytokine IL-6 was increased in split-housed mice. (A) Expression levels of the cytokines IL-6 and Iba-1 in the hippocampus (n = 8–10 per group). (B) Serum concentrations of the cytokines IL-6 and IL-17A. (n = 10 per group). Welch's ANOVA followed by Dunn’s test; *p < 0.05; Mean ± S.E.M.

(A) Split-housed mice showed higher expression levels of the cytokines IL-6 and Iba-1 in the hippocampus than pair-housed mice. (B) Split-housed mice showed a trend toward higher serum IL-6 (p = 0.0858) and significantly lower level of IL-17A than single-housed mice.

Data availability statement

All data generated or analyzed during this study are included in this published article and its supplementary information files.