Moderate Immunodepression Does Not Alter Some Murine Behaviors

This report investigates if a partial loss of immunity results in alterations of murine behaviors in the open field (ambulation, a correlate of exploration or extroversion, and defecation, a correlate of neuroticism); positive findings would implicate the immune system in the expression of the above behaviors. Twelve female mice and 12 male mice, of the outbred CD1 strain, received a daily injection of the immunosuppressive drug methotrexate, at 3 mg/kg/ injection, for several days, whereas 10 female mice and 9 male mice received an injection of saline. Once immunodepression was established, as revealed by impaired antibody responses to rat erythrocytes, the mice were tested in the open field, where ambulation, rearing, defecation, and grooming were recorded. The same behaviors were recorded before the course of methotrexate (baseline). Although methotrexate decreased the antibody response (i.e., it produced immunodepression), it did not affect the behaviors, which points to little participation of the specific immunity on the recorded behaviors.