Even Gentle Restraint Can Increase Stress In Lab Mice
The C57BL/6 mouse strain, also known as “black 6”, was developed at the Bussey Institute from C.C. Little’s C57BL strain originally created in the 1920s. These dark-coated mice are a popular model organism for a variety of biomedical research studies. The dark coat makes this a convenient strain for creating transgenic mice as they can be crossbred with congenic light coated 129 mice to produce disease models. The transgenic mice show lighter patches of hair growth than their non-transgenic cousins.
Black 6 mice have some unusual behavioral characteristics. They are sensitive to noise, odors, and are more prone to bite their handlers than other research models such as BALB/c mice. The dominant female black 6 mouse will “barber” its fellow females, leaving their cage mates with bald patches of hair and whiskers. They do not tolerate cold as well as other mice and will drink alcohol-based liquids willingly.
Another word of warning for Black 6 users! A recent publication using the Arbor Assays Corticosterone EIA Kit, K014-H, showed moderate movement restraint in black 6 mice increased levels of corticosterone over the control group. This subchronic stress altered vascular function, likely through an increase in the synthesis/release of endothelial nitric oxide (via eNOS), as well as nitric oxide production in the vascular smooth muscle (via iNOS).
The ability to measure corticosterone levels in less than 1 µL of tail bleed samples in 90 minutes without extraction is why the Corticosterone EIA Kit from Arbor Assays is preferred by researchers who measure stress markers. It is the most sensitive kit available on the market and its performance is surpassed only by the next-generation Chemiluminescent Corticosterone Immunoassay Kit, K014-C, from Arbor Assays, which provides an additional 2-3 fold increase in sensitivity.