The stress of intruding: reduction by chlordiazepoxide

Rats placed as intruders in a long-established colony showed significant elevations of plasma corticosterone after 10-20 minutes of intruding. This rise was prevented by 5 days pretreatment with chlordiazepoxide (5 mg/kg). The rats resident in the colony had significantly higher basal corticosterone concentrations compared with singly housed rats but the same as rats housed in groups of six in a normal cage. The resident rats showed no elevation of plasma corticosterone in response to 20 minutes of an intruder in the colony.