DISCRIMINATION OF ODORTYPES DETERMINED BY THE MAJOR HISTOCOMPATIBILITY COMPLEX AMONG OUTBRED MICE

Genetically determined body odors that distinguish one mouse from anot her are termed odortypes. The best known odortypes, highly expressed i n urine, are those specified by H-2, the major histocompatibility comp lex of the mouse, but other odortypes originate from unidentified loci in the rest of the genome, including both sex chromosomes. The defini tion of H-2 odortypes and evidence that their perception affects repro ductive behavior have so far depended on studies with inbred mouse str ains whose genetic differences are confined to the H-2 complex of gene s. To simulate feral conditions more closely, a freely segregating pop ulation was bred from crosses involving four unrelated inbred strains contributing four different H-2 haplotypes. After H-2 typing, this out bred population was divided into four groups of freely segregating mic e, comprising the four distinct H-2 genotypes represented, to serve as conventional donors of urine for evaluation in the standard Y-maze sy stem used in the training and testing of mice for H-2 odortype discrim ination. With respect to utility in training mice for H-2 odortype dis crimination, and to degrees of concordance attained in the Y-maze by t rained mice, these urinary H-2 odortype sources from outbred mice were no less effective than urines customarily obtained for those purposes from nonsegregating inbred donors. We conclude that discrimination of H-2 odortypes is not appreciably affected or impaired by the usual co ncurrent segregation within the genome as a whole.