Affiliative Behavior, Ultrasonic Communication and Social Reward Are Influenced by Genetic Variation in Adolescent Mice

Abstract

Social approach is crucial for establishing relationships among individuals. In rodents, social approach has been studied primarily within the context of behavioral phenomena related to sexual reproduction, such as mating, territory defense and parental care. However, many forms of social interaction occur before the onset of reproductive maturity, which suggests that some processes underlying social approach among juvenile animals are probably distinct from those in adults. We conducted a longitudinal study of social investigation (SI) in mice from two inbred strains to assess the extent to which genetic factors influence the motivation for young mice to approach one another. Early-adolescent C57BL/6J (B6) mice, tested 4–6 days after weaning, investigated former cage mates to a greater degree than BALB/cJ (BALB) mice, irrespective of the sex composition within an interacting pair. This strain difference was not due to variation in maternal care, the phenotypic characteristics of stimulus mice or sensitivity to the length of isolation prior to testing, nor was it attributable to a general difference in appetitive motivation. Ultrasonic vocalization (USV) production was positively correlated with the SI responses of mice from both strains. Interestingly, several USV characteristics segregated with the genetic background of young mice, including a higher average frequency and shorter duration for the USVs emitted by B6 mice. An assessment of conditioned place preference responses indicated that there was a strain-dependent difference in the rewarding nature of social contact. As adolescent mice aged, SI responses gradually became less sensitive to genetic background and more responsive to the particular sex of individuals within an interacting pair. We have thus identified a specific, genetic influence on the motivation of early-adolescent mice to approach one another. Consistent with classical theories of motivation, which propose a functional relationship between behavioral approach and reward, our findings indicate that reward is a proximal mechanism through which genetic factors affect social motivation during early adolescence.

Efficient Encoding of Vocalizations in the Auditory Midbrain

“…Mice are a model system for studying this because they possess a typical mammalian auditory system and they emit a wide repertoire of vocalizations under various social contexts (Panksepp et al, 2007;Wang et al, 2008). Despite the ubiquity and behavioral relevance of mouse ultrasonic (Ͼ20 kHz) vocalizations, we found an under-representation of neurons with CFs that matched the spectral content of the vocalization stimuli (25-102 kHz).…”

The clock genePeriod1regulates innate routine behaviour in mice

“…This is interesting since Per1 2/2 mice were reported to display a phenotype in the radial arm maze test for hippocampus-related memory [16,50]. It is not clear if this habituation reflects 'social recognition' or reduced salience of the female as a 'matingstimulus' in the context of the testing set-up [51,52]. In mice, which live in large social groups, such behaviour is important for both energy conservation (to avoid unnecessary fighting) and reproduction [1,2,39].…”

Reduced ultrasonic vocalizations in vasopressin 1b knockout mice

“…USVs emitted by resident Avpr1b −/− females were not only fewer but of qualitatively different frequencies from those emitted by Avpr1b +/+ and +/− females (30 kHz vs 50 kHz, approximately). The biological meaning of variation of USVs frequency in the adult mouse has been only sporadically investigated [30,38,54]. In rats, USV frequency has been related to aversive and appetitive states [8,28].…”