Operant task performance and corticosterone concentrations in rats housed directly on bedding and on wire.

The present experiment was designed to investigate the effect of housing conditions on task performance and corticosterone response. Two groups of male F344BNF1 rats were housed on a ventilated rack with ad libitum access to water and a restricted feeding regime. Group 1 was housed in solid-bottom caging with corn cob bedding, whereas group 2 was housed in wire-bottom caging. After learning an operant task, each rat was exposed to acute restraint followed 48 h later by exposure to continuous light. Corticosterone concentrations were determined before and after exposure to each intervention. Contrary to assumptions, housing did not affect task performance. Baseline corticosterone concentrations were similar for the 2 experimental groups, but corticosterone concentrations were significantly higher for the wire-bottom group than the solid-bottom group immediately after the restraint and remained elevated 2 d later. Corticosterone levels decreased in both groups after exposure to continuous light. Overall, the data indicate that subtle but significant differences occur in responses of rats housed on wire-bottom versus solid-bottom caging when the animals are exposed to acute restraint.