Searching for the Source of Urinary Odors of Individuality in Rodents

Abstract

Over the past several years we have investigated the genetic, microbiological and dietary factors involved in the production of urinary odors of individuality in rats and mice. The outcome of these experiments, conducted using two different paradigms, a habituation-dishabituation task and a go/no go operant procedure, are reviewed here. Results confirmed that the urinary odors of rats with genetic differences only at the major histocompatibility complex (MHC) can be discriminated by conspecifics. The selective removal of gut bacteria alters but does not eliminate urinary odors of individuality; however, the specific identity of the bacteria influencing the urinary odors has not been determined. The discrimination of urinary odors from MHC-congenic rats is disrupted when the diet of the donors is changed; however, the discrimination between urinary odors from two genetically identical rats on different diets is not disrupted when the urinary odors from rats of a MHC-congenic strain are substituted. Overall, the results indicate that (1) the odors of individuality are multidimensional, involving genetic, dietary and bacterial factors and (2) the methods used in studies of odor discrimination may bias the outcome.