Sex differences in emotionality in C3H/HeH mice, with hypogonadal mutant to distinguish activational effects of gonadal hormones

The C3H/HeH mouse strain has a mutant hypogonadal (hpg) variant, providing an animal model to examine the activational effects of sex hormones because reproductive maturation is arrested at a neonatal stage. Thus in the adult mouse, the circulating concentrations of sex steroids are extremely low. The present study used a series of tests to distinguish sex differences in behaviour: open field, locomotor activity, hyponeophagia, and novel location recognition. The results showed some evidence for a role of sex hormones in emotionality underscoring the potential utility of the hpg model, to distinguish activational effects in the C3H/HeH strain. However, the direction that the sex differences took varied by task: whilst males showed the predicted sex difference of relatively greater anxiety in the open field, hyponeophagia tests suggested higher emotionality in females. The hpg mice of both sexes showed a reduction in anxiety measured as hyponeophagia. Overall it can be concluded that this set of experiments supports the potential of the hpg model to investigate hormonal influences on emotionality. (C) 2008 Elsevier Inc. All rights reserved.