How to keep track of mouse urine
Eight hours is a long time without a trip to the bathroom when awake, yet most of us can sleep through the night without peeing. And no, it’s not just because you (presumably) stop drinking coffee in your sleep: even when food and drink are factored out, you both make less urine and have better bladder capacity during the night. As with most behaviors that change from day to night, it does indeed have everything to do with the circadian rhythm.
In a new study published in Nature Communications, researchers compared normal mice with mice whose circadian rhythms were disrupted by genetic mutations. To keep track of mice urination over time, they used a rather charming contraption that slowly unspooled urine paper under the cages (see image). Urine spots on the paper were counted up and, sure enough, urination in the normal mice showed 24-hour patterns while the mutant mice did not.