Characterization of Train-Induced Vibration and its Effect on Fecal Corticosterone Metabolites in Mice

Abstract

Excessive environmental vibrations can have deleterious effects on animal health and experimental results, but they remain poorly understood in the animal laboratory setting. The aims of this study were to characterize train-associated vibration in a rodent vivarium and to assess the effects of this vibration on the reproductive success and fecal corticosterone metabolite levels of mice. An instrumented cage, featuring a high-sensitivity microphone and accelerometer, was used to characterize the vibrations and sound in a vivarium that is near an active railroad. The vibrations caused by the passing trains are 3 times larger in amplitude than are the ambient facility vibrations, whereas most of the associated sound was below the audible range for mice. Mice housed in the room closest to the railroad tracks had pregnancy rates that were 50% to 60% lower than those of mice of the same strains but bred in other parts of the facility. To verify the effect of the train vibrations, we used a custom-built electromagnetic shaker to simulate the train-induced vibrations in a controlled environment. Fecal pellets were collected from male and female mice that were exposed to the simulated vibrations and from unexposed control animals. Analysis of the fecal samples revealed that vibrations similar to those produced by a passing train can increase the levels of fecal corticosterone metabolites in female mice. These increases warrant attention to the effects of vibration on mice and, consequently, on reproduction and experimental outcomes.

Figure 1.

Diagram of measurement cage.

Figure 2.

Summary of when feces were collected and vibrations were completed

Figure 3.

Top and side views of the constructed electromagnetic shaker.

Figure 4.

Typical vibrations in the test room with mice on the flat rack.

Figure 5.

Typical vibrations in the test room without mice on the flat rack but with equivalent weight added.

Figure 6.

Typical equivalent continuous sound level of the test room.

Figure 7.

FCM levels (mean ± SE) of the female mice. The triangles indicate the times at which vibrations were induced with the electromagnetic shaker; the vertical line indicates the day-to-night transition.

Figure 8.

FCM levels (mean ± SE) of the male mice. The triangles indicate the times at which vibrations were induced with the electromagnetic shaker; the vertical line indicates the day-to-night transition.