Zernig Gerald, Ghareh Hussein, Berchtold Helena
Department of Pharmacology, Medical University of Innsbruck, Peter Mayr Strasse 1 a, 6020 Innsbruck, Austria.
Biology (Basel). 2022 Feb 11;11(2):291. doi: 10.3390/biology11020291.
Rats, including those of the Sprague Dawley strain, may kill mice. Because of this muricidal behavior, it is standard practice in many research animal housing facilities to separate mice from rats (i.e., the predators) to minimize stress for the mice. We tested the effect of cohousing on the stress levels of mice from either the C57BL/6J (BL6) or the CD1 strain and Sprague Dawley rats (SD rat) by quantifying their fecal corticosterone and metabolites (FCM) concentration. We also investigated cohousing impacts a behavioral assay, i.e., conditioned place preference for intragenus (i.e., mouse-mouse or rat-rat) dyadic social interaction (DSI CPP) that was shown be sensitive to social factors, especially to handling by humans. We found that the two delivery batches of BL6 mice or SD rats, respectively, had different stress levels at delivery that were statistically significant for the BL6 mice. Even so, the BL6 mice cohoused with rats had significantly increased FCM concentrations, indicative of higher stress levels, as compared to (1) BL6 mice housed alone or (2) BL6 mice at delivery. In contrast to their elevated stress levels, the attractiveness of contextual cues associated with mouse-mouse social interaction (DSI CPP) even increased in rat-cohoused BL6 mice, albeit non-significantly. Thus, cohousing BL6 mice and rats did not impair a behavioral assay in BL6 mice that was proven to be sensitive to handling stress by humans in our laboratory. SD rats cohoused with BL6- or CD1 mice, and CD1 mice cohoused with SD rats, showed DSI CPP that was not different from our previously published data on SD rats and BL6 mice of the Jackson- or NIH substrain obtained in the absence of cohousing. CD1 mice cohoused with rats did not show an increased FCM concentration compared to delivery. Our findings suggest that the effect of cohousing rats and mice under the conditions described above on their stress levels as opposed to their behavior might be less clearcut than generally assumed and might be overriden by conditions that cannot be controlled, i.e., different deliveries. Our findings can help to use research animal housing resources, which are usually limited, more efficiently.
包括斯普拉格-道利品系在内的大鼠可能会杀死小鼠。由于这种杀鼠行为，在许多实验动物饲养设施中，将小鼠与大鼠（即捕食者）分开是标准做法，以尽量减少小鼠的压力。我们通过量化粪便皮质酮及其代谢物（FCM）浓度，测试了合笼饲养对C57BL/6J（BL6）品系或CD1品系小鼠以及斯普拉格-道利大鼠（SD大鼠）应激水平的影响。我们还研究了合笼饲养对一种行为测定的影响，即种内（即小鼠-小鼠或大鼠-大鼠）二元社会互动（DSI CPP）的条件性位置偏爱，该测定已被证明对社会因素敏感，尤其是对人类的处理敏感。我们发现，两批分别交付的BL6小鼠或SD大鼠在交付时具有不同的应激水平，这对BL6小鼠来说具有统计学意义。即便如此，与（1）单独饲养的BL6小鼠或（2）交付时的BL6小鼠相比，与大鼠合笼饲养的BL6小鼠的FCM浓度显著增加，表明应激水平更高。与它们升高的应激水平相反，在与大鼠合笼饲养的BL6小鼠中，与小鼠-小鼠社会互动（DSI CPP）相关的情境线索的吸引力甚至有所增加，尽管不显著。因此，将BL6小鼠与大鼠合笼饲养并未损害BL6小鼠的一种行为测定，在我们实验室中，该测定已被证明对人类处理应激敏感。与BL6或CD1小鼠合笼饲养的SD大鼠，以及与SD大鼠合笼饲养的CD1小鼠，表现出的DSI CPP与我们之前发表的关于在不合笼情况下获得的杰克逊或NIH亚系的SD大鼠和BL6小鼠的数据没有差异。与交付时相比，与大鼠合笼饲养的CD1小鼠的FCM浓度没有增加。我们的研究结果表明，在上述条件下将大鼠和小鼠合笼饲养对它们应激水平的影响，与对它们行为的影响相比，可能没有通常认为的那么明确，并且可能会被无法控制的条件（即不同的交付批次）所掩盖。我们的研究结果有助于更有效地利用通常有限的实验动物饲养资源。
