Behavior and severity of adjuvant arthritis in four rat strains

Previous research has suggested that behavioral traits of the histocompatib le Lewis and Fischer strains of rats could be related to the difference in their susceptibility to adjuvant arthritis (AA), In the present study, the predictive value of behavioral markers in susceptibility to AA was investig ated in nonhistocompatible inbred DA, Lewis, Albino Oxford (AO), and outbre d Wistar strain. Behavioral profiles (open filed test and forced swim test) were determined prior to immunization with a single intradermal injection of complete Freund's adjuvant. Animals were daily scored for clinical signs of AA. The occurrence of certain behaviors and clinical indices of AA was significantly associated with strain membership. Discriminant analysis iden tified strain-related behavioral and illness profiles with very few overlap s among the phenotypes. Discriminant classification significantly exceeded the proportion of cases, which could have been correctly classified on the basis of chance. Open field behavior, in particular, exploration and groomi ng, differentiated among AA-susceptible and AA-resistant strains. Multiple regression analysis indicated that severity of AA (maximum clinical sign) c an be predicted by the latency time and grooming behavior in the open field independently of strain membership. No clear distinction between AA-suscep tible and AA-resistant strains was found with respect to forced swim test i mmobility. It was concluded that (a) strain-related genetic predisposition is important for the expression of certain behavioral traits and for suscep tibility to AA and (b) open field behaviors, particularly grooming and late ncy, predict susceptibility to AA across different rat strains. (C) 2001 Ac ademic Press.