Housing conditions and stimulus females: a robust social discrimination task for studying male rodent social recognition

Abstract

Social recognition (SR) enables rodents to distinguish between familiar and novel conspecifics, largely through individual odor cues. SR tasks utilize the tendency for a male to sniff and interact with a novel individual more than a familiar individual. Many paradigms have been used to study the roles of the neuropeptides oxytocin and vasopressin in SR. However, inconsistencies in results have arisen within similar mouse strains, and across different paradigms and laboratories, making reliable testing of SR difficult. The current protocol details a novel approach that is replicable across investigators and in different strains of mice. We created a protocol that uses gonadally intact, singly housed females presented within corrals to group-housed males. Housing females singly before testing is particularly important for reliable discrimination. This methodology will be useful for studying short-term social memory in rodents, and may also be applicable for longer term studies.

Figure 1

The social discrimination task. (a) Photograph depicting placement of corrals within the test cage. (b) A cartoon representation of Trial 1, which consists of exposure to a single corralled female. (c) A cartoon representation of Trial 2, which consists of simultaneous presentation of the “familiar” female (white) and exposure to a second “novel” female (gray). This occurs after a pre-determined delay between Trial 1 and Trial 2.

Fig 2

Results using different permutations of the social discrimination task. (a) Representative data of investigation times of corralled C57Bl/6J females by group-housed C57Bl/6J males. (b) Investigation time during Trial 1 (single female in one corral) when the empty corral remains in the test cage (left) or is removed during testing (right). (c) Investigation time during Trial 1 (single female in one corral) by group-housed and single-housed males (p = 0.06 between bars). (d) Significant discrimination occurred between “familiar” and “novel” females by group housed males only when singly-housed stimulus females were used (right); ***p < 0.001 between familiar and novel via paired-samples t-test. For all graphs, data are mean ± SEM; n = 10 per group.

Fig 3

Performance on the social discrimination task in three lines of knockout (−/−) mice. Data are mean ± SEM for investigation of a familiar and a novel mouse. Each line was tested three times, with 2 weeks between tests. Differences in exploration of familiar and novel females were assessed via paired samples t test (a) Oxt^−/− males and (b) Oxtr^−/− males discriminated only between familiar and novel Swiss-Webster (SW) females. (c) Oxtr^FB/FB males did not discriminate between any of the three strains of stimulus females presented. *p < 0.05; **p < 0.01. Adapted from Macbeth et al., 2009.