Genotype, uterine position, and testosterone sensitivity in older female mice

CF-1 and CK (C57BL/6J x AKr) female mice that developed in utero between two males (2M), adjacent to one male (1M), or between two females (0M) were tested for their sensitivity to the aggression-promoting property of testosterone (T) beginning at 9 months of age. Comparisons between the strains showed that a higher proportion of CF-1 females fought in response to T and that the period of hormone exposure required to induce aggression also was shorter in this strain. Within each of the genotypes, there were no systematic differences in responsiveness to T related to contiguity to males during fetal development. While the results provide further evidence for genotype as a major influence on neural sensitivity to androgen, they do not support uterine position of females relative to males as a source of phenotypic variation in responsiveness.