Social features of scent-donor mice modulate scent marking of C57BL/6J recipient males

Abstract

Territorial male mice can form familiarity-dependent amicable relationships, suggesting that they manage their territorial aggressiveness based on individual recognition, which may be mediated by olfactory signals. The present study demonstrated modulatory effect of odorant cues from mice of different social/housing groups on territorial scent marking by C57BL/6J males. Pair-housed males deposited few scent marks in a novel situation without mouse odors, while singly-housed males marked more in the same situation (Experiment 1). However, when confronted by a conspecific, singly-housed males made fewer marks to pair-housed than to singly-housed stimulus males, while pair-housed males showed few marks to either stimulus animal (Experiment 2). Reduction in scent marking in singly-housed males was also seen on exposure to urine scent alone from a pair-housed male, indicating that the inhibitory cue is mediated by urinary odor (Experiment 3). This inhibitory odor was effective even when singly-housed males were placed in a no-odor environment following exposure to soiled bedding used by pair-housed males (Experiment 4). When singly-housed males were exposed to scent from subordinate males, they showed less marking than when the stimulus scent was from dominants or singly-housed males (Experiment 5). Scent marking was not influenced by the total amount of urine scent marks deposited on the substrates (Experiment 6), suggesting that it is a particular component in urinary odor rather than the magnitude of the odor, that plays a significant role in recipient behavior. Together, these experiments indicate that conspecific male odor signals modulate territorial scent marking behavior in mice.

Figure 1

The mean number of squares with scent marks on the substrates in no-odor chamber for each group of singly- or pair-housed mice. Data are expressed as mean ± S.E.M. Significant differences between groups; **p<.01.

Figure 2

The mean number of squares with scent marks on the substrates for each group of singly- or pair-housed males, when confronted with a stimulus animal of singly- (to S-st) or pair-housed (to P-st) via wire mesh. Data are expressed as mean ± S.E.M. Significant post hoc differences between groups; * p<.05, **p<.01.

Figure 3

The mean number of squares with scent marks made by singly-housed (a) or pair-housed (b) males. They were confronted with each of three stimulus conditions; No odor (subjects alone), Odor (scent marks deposited on the paper substrate by a pair-housed B6), and pair-housed B6 (A stimulus B6 mouse that was pair-housed). Data are expressed as mean ± S.E.M. Significant post hoc differences between groups compared to No-odor condition; * p<.05.

Figure 4

The mean number of squares with scent marks made by singly-housed (a) or pair-housed (b) males. They were exposed to an empty chamber immediately following a 20-min placement into one of three different cages; Clean (cages with clean sawdust), S-cage (cages with soiled sawdust occupied by a singly-housed mouse prior to the test), and P-cage (cages with soiled sawdust in which two mice were housed together). Data are expressed as mean ± S.E.M. Significant post hoc differences between groups compared to Clean cage condition; * p<.05.

Figure 5

The mean number of squares with scent marks on the substrate for each group of (a) stimulus animals and (b) the subjects. Stimulus animals were divided into three conditions; Singly (A singly-housed male), Dominants, or Subordinates, were placed in a novel, no-odor environment for 20 min. After urinary scent was collected from the stimulus animals, singly-housed subjects were exposed to each of these urinary scents on the other side of a wire mesh for 20 min. Data are expressed as mean ± S.E.M. Significant post hoc differences between groups compared to Singly condition; * p<.05.

Figure 6

The mean number of squares with scent marks for each group of (a) the stimulus animals or (b) subjects. The paper substrates from singly-housed stimulus animals were cut in half for the half size group and were not cut for the full size group. Each of these paper substrates was exposed to a singly-housed subject for 20 min. Data are expressed as mean ± S.E.M. Significant differences between groups; * p<.05.