Different stress-related phenotypes of BALB/c mice from in-house or vendor: alterations of the sympathetic and HPA axis responsiveness

Abstract

Background: Laboratory routine procedures such as handling, injection, gavage or transportation are stressful events which may influence physiological parameters of laboratory animals and may interfere with the interpretation of the experimental results. Here, we investigated if female BALB/c mice derived from in-house breeding and BALB/c mice from a vendor which were shipped during their juvenile life differ in their HPA axis activity and stress responsiveness in adulthood.

Results: We show that already transferring the home cage to another room is a stressful event which causes an increased HPA axis activation for at least 24 hours as well as a loss of circulating lymphocytes which normalizes during a few days after transportation. However and important for the interpretation of experimental data, commercially available strain-, age- and gender-matched animals that were shipped over-night showed elevated glucocorticoid levels for up to three weeks after shipment, indicating a heightened HPA axis activation and they gained less body weight during adolescence. Four weeks after shipment, these vendor-derived mice showed increased corticosterone levels at 45-min after intraperitoneal ACTH challenge but, unexpectedly, no acute stress-induced glucocorticoid release. Surprisingly, activation of monoaminergic pathways were identified to inhibit the central nervous HPA axis activation in the vendor-derived, shipped animals since depletion of monoamines by reserpine treatment could restore the stress-induced HPA axis response during acute stress.

Conclusions: In-house bred and vendor-derived BALB/c mice show a different stress-induced HPA axis response in adulthood which seems to be associated with different central monoaminergic pathway activity. The stress of shipment itself and/or differences in raising conditions, therefore, can cause the development of different stress response phenotypes which needs to be taken into account when interpreting experimental data.

Figure 1

Differences of stress responses of in-house-bred and vendor-derived, shipped mice. A, B. Plasma corticosterone levels (A; ANOVA: F = 9.169; p < 0.001) and blood lymphocyte counts (B; ANOVA: F = 70.87; p < 0.001) of acutely stressed (black bars) and non-stressed mice (white bars) four weeks after room change (in-house bred) or shipment from vendor; n = 12 mice/group; summary of two independent experiments giving similar results. C. ACTH-induced (grey bars) and BSA control treatment-induced (white bars) plasma corticosterone levels measured four weeks after shipment from vendor or room change of in-house bred mice (ANOVA: F = 80.15; p < 0.001); n = 2 experiments; n = 6 mice/group; *p < 0.05, **p < 0.01, ***p < 0.001 compared with in-house bred, acutely stressed or ACTH-challenged group; ^###p < 0.001 compared with in-house bred, non-stressed group; ^††p < 0.01 compared with vendor-derived control group; comparison by Tukey test.

Figure 2

Kinetics of glucocorticoid levels and lymphocyte counts after transportation stress. A. Plasma corticosterone levels of female mice that were shipped for 18 h from vendor at the age of six weeks compared with gender and age-matched animals of in-house breeding that only underwent room change; measured immediately after transport, one day later and in the following three weeks (ANOVA for effects of breeding conditions F = 9.4, p < 0.0046; ANOVA for effects of time F = 6.03, p = 0.0011). B, C. Kinetics of total white blood cells (WBCs) and lymphocyte counts in the blood of mice after over-night transport from vendor compared with lymphocyte numbers of animals from own breeding facility (ANOVA for effects of breeding conditions F = 0.53, p = 0.4711; ANOVA for effects of time F = 3.02, p = 0.033); n = 4-20 mice/group *p < 0.05, **p < 0.01 comparison with basal levels of healthy control mice; ^##p < 0.01, ^###p < 0.001 comparision with vendor-derived mice at day 22; comparison by Turkey testing.

Figure 3

Different body weight gain during adolescence of in-house bred and vendor-derived mice. Kinetics of body weight gain 6-10 weeks after birth of mice that underwent 18 h-lasting over-night shipment from vendor compared with animals from own breeding facility, n = 4-20 mice/group. (ANOVA for effects of breeding conditions F(8) = 26.74, p < 0.0001; ANOVA for effects of time F(8) = 20.97, p < 0.0001); *p < 0.05, **p < 0.01, ***p < 0.001 compared to day 1 in the in-house bred group; ^#p < 0.05, ^##p < 0.01, ^###p < 0.001 compared to day 1 in the vendor-derived group; ⁺p < 0.05 compared with day 22 in the in-house-bred group; comparison by Tukey testing.

Figure 4

Different acute stress response with or without reserpine treatment of in-house bred and vendor-derived mice. Plasma corticosterone levels (A, ANOVA: F = 8.275, p = 0.0002) and lymphocyte counts of in-house bred (B, ANOVA: F = 114.6, p < 0.0001) as well as corticosterone levels (C, ANOVA: F(4) = 13.39, p < 0.0001) and lymphocyte counts in the blood of vendor-derived, shipped mice (D, ANOVA: F(4) = 42.48, p < 0.0001) immediately after acute stress exposure (black bars) compared with non-stressed animals (white bars). Mice were either pre-treated with reserpine in order to block sympathetic output during stress or control-treated with NaCl. n = 12 mice/group representative for two experiments giving similar results; *p < 0.05, **p < 0.01, ***p < 0.001 compared with NaCl treated, non-stressed mice, ^###p < 0.001 compared with reserpine treated, non-stressed mice, ^†††compared with NaCl treated, acutely stressed mice; comparison by Tukeys' test.