The Effects of Social Hierarchy Establishment in Resident–Intruder Model on Testicular Function in Laboratory Mice of Different Inbred Strains

Abstract

Male reproductive success is known to be related with ability to social dominance and number and quality of spermatozoa as well as the production of reproductive hormones. The relationships between social dominance and testicular function are affected by genotype and environmental conditions of social hierarchy formation, and male territorial status (resident or intruder). However, the mechanisms of these relationships are still poorly understood. The aim of this study was to investigate effects of genotype and of familiarization with the habitat on testicular function during social hierarchy formation in experimental model of social hierarchy in laboratory mice using resident-intruder paradigm. Male of certain inbred strain (PT or CBA/Lac strain) was placed to experimental cage where male (resident) of other inbred strain (PT or CBA/Lac strain) has been living two days with female of DD/He strain. Social rank for each male was assessed after social hierarchy formation. Then testosterone level in serum and testes and epydidymal sperm quality were estimated after five days after the group formation. It was shown that social hierarchy formation did not affect testosterone level in serum and testes as well as percentage of sperm heads with abnormal morphology. However, the establishment of social hierarchy resulted in decreased sperm number in dominant-intruders of PT strains as well as decreased progressive sperm motility in subordinants of CBA/Lac strain regardless territorial status. To conclude, social hierarchy formation in experimental model of social hierarchy in laboratory mice affects epididymal sperm quality already five days after group formation, with pattern of these relationships depending on genotype, social rank and territorial status.