INTERMALE AGGRESSION TESTED IN 2 PROCEDURES, USING 4 INBRED STRAINS OF MICE AND THEIR RECIPROCAL CONGENICS - Y-CHROMOSOMAL IMPLICATIONS

Indications of a role for the nonpseudoautosomal region of the Y chrom osome (Y-NPAR) in intermale attack behavior have been demonstrated by Maxson's group using C57BL/10 (B10) and DBA/1 (D1) inbred mouse strain s and their reciprocal congenics. Carlier and Roubertoux' group, using CBA/H (H) and NZB/B1NJ (N) mice, did not find such a Y-NPAR effect. F or the two research groups, however, not only were the parental strain s different, but also the rearing conditions and testing methods. The divergent conclusions drawn may therefore have been due either to gene tic variation or to environment-related variables. We carried out two experiments to investigate these alternatives. The N and H strains wer e raised and tested according to the experimental design used by Maxso n's group (homogeneous set test) and the D1 and B10 strains were raise d and tested according to the experimental design of Carlier and Roube rtoux' group (standard opponent test). Considering all studies togethe r, the Y-NPAR effect appeared in both sets of mice only when using the homogeneous set test. This raises the question of what environmentall y related variables are involved in the Y-NPAR effect on intermale att ack. One strong hypothesis is that the different types of opponents in each experimental design send differing olfactory signals, which, in turn, differentially affect the capacity to elicit intermale attack be havior.