Training rats to discriminate between the odors of individual conspecifics

Abstract

To determine the influence of genetic and microbiological factors in producing individually unique urine odors, we used a go/no-go operant task to assess the ability of eight male Long-Evans rats to discriminate between urine odors from the following pairs of male rats: (1) two outbred Long-Evans rats, (2) individual conventionally housed rats differing genetically only at the major histocompatibility complex (PVG vs. PVG.R1), (3) individual PVG versus PVG.R1 rats born by cesarean section and raised in germfree conditions, and (4) conventionally housed, genetically identical individuals of the PVG or PVG.R1 strains. Discriminable differences were present between the urine odors used in all four tasks. Analysis of the errors to a criterion of 85% correct discrimination responses revealed different learning patterns in each task. When bacteria were not present in genetically different rats (Task 3) and when bacteria were present but there were no genetic differences between rats (Task 4), the discrimination was the most difficult. The easiest discrimination involved the presence of bacteria and a genetic difference at the major histocompatibility complex (Task 2). These results indicate that, although bacteria are not necessary for the production of discriminable odor differences, they do influence the discriminability of the urine odors of rats. © 1991 Psychonomic Society, Inc.