For instance, Dr. Feng and colleagues said, anxious mice tend to stick close to the walls of a circular open cage, while less timid animals spend more time exploring the open center.
The knockout mice, over a half-hour test, averaged less than 10% of their time in the center of the test apparatus, while wild-type mice spent between 20% and 35% of the time in that region. The differences were significant at P<0.05 and P<0.01, depending on the time during the test.
"We were surprised by the magnitude of this phenomenon," Dr. Feng said. "The parallels with OCD were pretty striking."
Treating the animals with fluoxetine(Drug information on fluoxetine) for six days -- once a day at 5 mg/kg -- significantly reduced the excessive grooming in the knockout mice (at P<0.01) but had no effect on wild-type mice.