Location response to a startling noise depends on the preferred grooming site in mice

The exploratory behavior of adult male Balb/c mice was observed in both a small black box and an open field. The normal exploratory pattern included a strong tendency to groom in a preferred place (G-site); thus, an average of 86% (black box) and 92% (open field) of the total grooming time was spent in a single location, specific for each animal and environment. The response of the animals to a 2-sec, 100 dB auditory stimulus varied according to their location. If the unexpected sound occurred when the mice were in their G-site, they remained there an average of 67% (black box) and 75% (open field) of the trials. If elsewhere, they escaped and ran to their G-site 89% (black box) and 73% (open field) of the times. Mice treated with diazepam (5 mg/kg) showed the normal tendency to groom in a preferred place, but never escaped after the stimulus, even if it occurred when they were outside their G-site, nor did they resume normal exploratory behavior. It seems that the preferred grooming location is the place that serves as a refuge from an aversive noise signal, but only the latter behavior is abolished by diazepam, presumably by reduction of stress.