The coagulating glands as a source of aversive and aggression-inhibiting pheromone(s) in the male albino mouse

Exocrine scent marking: Coordinative role of arginine vasopressin in the systemic regulation of social signaling behaviors

Arginine vasopressin (AVP) is a neurohypophysial hormone that coordinatively regulates central socio-emotional behavior and peripheral control of antidiuretic fluid homeostasis. Most mammals, including rodents, utilize exocrine or urine-contained scent marking as a social signaling tool that facilitates social adaptation. The exocrine scent marking behavior is postulated to fine-tune sensory and cognitive abilities to recognize key social features via exocrine/urinary olfactory cues and subsequently control exocrine deposition or urinary marking through the mediation of osmotic fluid balance. AVP is implicated as a major player in controlling both recognition and signaling responses. This review provides constructive hypotheses on the coordinative processes of the AVP neurohypophysial circuits in the systemic regulations of fluid control and social-communicative behavior, via the expression of exocrine scent marking, and further emphasizes a potential role of AVP in a common mechanism underlying social communication in rodents.

Changes in male odours and urinary marking patterns due to inhibition of aggression in male mice

The effects of active inhibition of aggression on male odours and urinary marking patterns were studied in mice belonging to a highly aggressive strain the TA (Turku Aggressive), which has been developed by selective breeding through 37 generations. These males were defeated by trained fighters until they showed no aggression. Individually housed TA males served as controls. Mice from the parental or Normal Strain, which is intermediate in aggression, were exposed to the odours. The males from the Normal Strain were tested for aggression against male castrates to which urine from the two types of TA males or water had been applied. The urine from the highly aggressive control TA males evoked most aggression. The Normal males were later tested against castrates on soiled sawdust. Fewer attacks occured on sawdust soiled by the urine from the control TA males. The preferences for areas covered with soiled sawdust were also assessed. The males from the Normal Strain preferred areas soiled by the TA males trained to nonaggressiveness while the females preferred areas soiled by the highly aggressive control TA males. Subsequently the size and number of urinary marks deposited were examined. The TA males trained to nonaggressiveness voided urine in fewer but larger pools. The differences showed the same direction as those previously found between the TA and TNA strains, selectively bred for aggression and non-aggression, respectively. In mice the odour signals and urinary marking patterns seem to be correlated with the level of aggressiveness, either hereditarily determined or acquired through learning.

Possible chemical basis for histocompatibility-related mating preference in mice

High-resolution chromatographic profiles of urinary volatiles were quantitatively recorded and statistically evaluated for the female mice genetically differing in a small region of the major histocompatibility complex on the 17th chromosome. Both immature and estrogenized animals were evaluated. While there seem to be no specific volatile products of the histocompatibility genes, statistically significant differences were readily observed with the immature females of different haplotypes, involving the general range of secondary volatile metabolites. Their possible role in olfactory communication is discussed.

Chemical differences between voided and bladder urine in the aye-aye (Daubentonia madagascariensis): implications for olfactory communication studies

Urine serves a communicative function in many mammalian species. In some species, the signaling function of urine can be enhanced by the addition of chemical compounds from glands along the distal portion of the urogenital tract. Although urine marking is the main mode of chemical communication in many primate species, there has been no study of the contribution of urogenital secretions to the chemical complexity of primate urine. Here, we compared the chemical composition of bladder urine versus voided urine in the aye-aye, Daubentonia madagascariensis, a strepsirrhine primate that relies on urine in intraspecific communication. Both types of urine, collected from each of 11 aye-ayes representing both sexes of varying adult ages, underwent headspace analysis via gas chromatography and mass spectrometry. Although the average number of compounds was similar in bladder and voided urine, 17% of the compounds detected occurred exclusively in voided urine (but only in a subset of individuals). An overall measure of chemical complexity (using a nonmetric multidimensional scaling analysis) showed that both types of urine were chemically different at the individual level. There was no apparent sex or age differences in the chemical components found in aye-aye urine. Nonetheless, the individual dissimilarities between bladder urine and voided urine indicate chemical contributions from structures along the urogenital tract and offer further support for the relevance of urinary communication in the aye-aye.

Communication impairments in mice lacking Shank1: reduced levels of ultrasonic vocalizations and scent marking behavior

Autism is a neurodevelopmental disorder with a strong genetic component. Core symptoms are abnormal reciprocal social interactions, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior with restricted interests. Candidate genes for autism include the SHANK gene family, as mutations in SHANK2 and SHANK3 have been detected in several autistic individuals. SHANK genes code for a family of scaffolding proteins located in the postsynaptic density of excitatory synapses. To test the hypothesis that a mutation in SHANK1 contributes to the symptoms of autism, we evaluated Shank1(-/-) null mutant mice for behavioral phenotypes with relevance to autism, focusing on social communication. Ultrasonic vocalizations and the deposition of scent marks appear to be two major modes of mouse communication. Our findings revealed evidence for low levels of ultrasonic vocalizations and scent marks in Shank1(-/-) mice as compared to wildtype Shank1(+/+) littermate controls. Shank1(-/-) pups emitted fewer vocalizations than Shank1(+/+) pups when isolated from mother and littermates. In adulthood, genotype affected scent marking behavior in the presence of female urinary pheromones. Adult Shank1(-/-) males deposited fewer scent marks in proximity to female urine than Shank1(+/+) males. Call emission in response to female urinary pheromones also differed between genotypes. Shank1(+/+) mice changed their calling pattern dependent on previous female interactions, while Shank1(-/-) mice were unaffected, indicating a failure of Shank1(-/-) males to learn from a social experience. The reduced levels of ultrasonic vocalizations and scent marking behavior in Shank1(-/-) mice are consistent with a phenotype relevant to social communication deficits in autism.

Female urine-induced male mice ultrasonic vocalizations, but not scent-marking, is modulated by social experience

Despite the evidence for a communicative function of rodent scent marks and ultrasonic vocalizations, relatively little is known about the impact of social factors on these two forms of communication. Here, we tested the effects of two important social factors, prior exposure to a female and freshness of female urine, on male scent marks and ultrasonic vocalizations elicited by female urine. We also asked whether a recently reported strain difference between the highly social strain C57BL/6J (B6) and the mouse model of autism BTBR T+tf/J (BTBR) herein is specifically seen in response to female urine or also detectable in response to male urine traces. Results show that the emission of female urine-elicited ultrasonic vocalizations was dependent on previous female experience, while scent-marking behavior was not affected. A positive correlation was detected between scent-marking behavior and ultrasonic calling in the most biologically relevant context, male mice exposed to fresh female urine after female experience. Correlations were less prominent or missing in less biologically relevant contexts, e.g. in male mice exposed to fresh female urine without previous female experience, indicating that previous female experience is affecting both the emission of female urine-elicited ultrasonic vocalizations and the correlation between olfactory and acoustic communication. The strain difference in scent-marking behavior and ultrasonic calling between B6 and BTBR appears to be specific to female urine-elicited behavior as it was not seen in response to male urine traces, highlighting the relevance of the social context in which mouse communication is evaluated.

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

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.

Scent marking behavior as an odorant communication in mice

In rodents, where chemical signals play a particularly important role in determining intraspecies interactions including social dominance and intersexual relationships, various studies have shown that behavior is sensitive to conspecific odor cues. Mice use urinary scent marks for communication with individual conspecifics in many social contexts. Urinary scent involves genetic information about individuals such as species, sex, and individual identity as well as metabolic information such as social dominance, and reproductive and health status, which are mediated by chemical proteins in scent marks including the major histocompatibility complex and the major urinary proteins. The odor of the predator which can be considered to be a threatening signal for the prey also modulate mouse behavior in which scent marking is suppressed in response to the cat odor exposure in mice. These odorant chemicals are detected and recognized through two olfactory bulbs, the role of which in detection of chemosignals with biological relevant appears to be differential, but partly overlapped. Mice deposit scent marks toward conspecifics to maintain their social relationships, and inhibit scent marking in a context where natural predator, cat odor is contained. This suppression of scent marking is long-lasting (for at least 7 days) and context-dependent, while the odorant signaling to conspecifics tends to appear frequently (over 24h but less than 7 days intervals) depending on the familiarity of each signal-recipient. It has been discussed that scent marking is a communicative behavior associated with territoriality toward conspecifics, indicating that the social signaling within species are sensitive to predator odor cues in terms of vulnerability to predation risk.

Social housing influences the composition of volatile compounds in the preputial glands of male rats

In rodents the preputial glands are one of the major sources of pheromones. These volatile chemosignaling compounds are known to elicit specific behavioral and physiological effects in their conspecifics. While social stress can alter both the behavior and hormonal status of rodents, little is known about its influence on the volatile constituents of the preputial glands. We have examined the composition of volatile compounds in the preputial glands of gonadally intact male rats housed for 70 days in either unisex triads (three/cage) or singly. The rank status of triad-housed rats was based on quantitative behavioral assessments taken during the initial 30 min of triad housing. Dominant rats had heavier preputial glands compared to subdominant and subordinate rats. Capillary gas chromatography-mass spectrometry identified 56 volatile preputial compounds, of these 17 did not differ between groups while 26 compounds were significantly higher in the single-housed compared to the triad-housed rats. Six additional volatile compounds were higher in the dominant compared to the other 3 groups, while another six compounds were higher in both the dominant and single-housed rats compared to the subdominant and subordinate rats. It can be concluded that both housing condition and social rank status have significant but different effects on the composition of volatile compounds found in preputial glands of male rats. The physiological and behavioral significance of these changes in preputial gland volatile compound composition in rats remain to be investigated.

Evidence of chemical communication in the spiny rat Trinomys yonenagae (Echimyidae): anal scent gland and social interactions

Behavioral and histological data reveal that Trinomys yonenagae, a colonial and fossorial caviomorph rodent, emits direct chemical signals through a single, highly developed, eversible anal sebaceous gland. Connective tissue covers the secretory portion of the gland, dividing it into smaller incomplete lobules. Well-defined layers of striated muscle fibers, which are organized in a crisscrossed manner, surround the external surface of the gland. These features indicate active secretion, and may be important for gland eversion. The frequency of gland eversion was zero when either males or females explored a new territory singly. However, when two unacquainted adults were paired independently of the sex, the anal gland was everted without scent being applied to the substrate or conspecifics. The chemical signaling was concomitant with the occurrence of investigative behaviors such as nose–nose, nose–rump, and nose–anus contact. Anal-gland protrusion did not evoke avoidance responses and agonistic behaviors were never observed. The data do not support the function of the short-lived signal as either a sex attractant or a scent mark. The potential importance of chemical signaling in T. yonenagae by means of an eversible gland may lie in recognizing individuals or classes of individuals, minimizing aggression, and increasing social cohesion, all of which are important to colonial animals.

Artificially increasing scent mark rate increases urogenital gland size in mice Mus musculus

Male mice produce scent marks by depositing urine throughout their territory. The scent marks contain a number of pheromones and contain major urinary proteins (MUPs). Up to 1 g of these MUPs may be produced everyday. It is therefore likely that scent marking is costly and as such will impact on male fitness. In order to investigate the costs of scent marking, we conducted an experiment where scent marking rate was increased artificially, without changing the social environment (which may have an independent and different effect on both scent marking and physiology), or changing travelling time (such as would occur in a larger territory). Novel objects were introduced every other day (Replace); objects were introduced on day 1 and moved on alternate days (Move); or the mice were left undisturbed (Control). Introducing new objects daily caused a significant increase in scent marking rate, and an increase in the size of both the coagulating gland and the testes compared to the other two conditions. This is likely to be due to increased hormonal activity, which is known to affect these gland sizes. Interestingly, the preputial gland, which produces a number of pheromones, did not differ between the three conditions. There were no differences in male weight, growth rate or condition, indicating that the effect of an increase in scent marking of this magnitude does not have measurable fitness effects.

Of mice and kin: the functional significance of kin bias in social behaviour

1. Sharing recent ancestry (kinship) increases the degree of genetic similarity between individuals, where genetic similarity could mean anything from sharing a particular allele to sharing an entire genome. 2. Genetic similarity can influence behavioural and other responses between individuals in a number of ways, discriminatory and non-discriminatory. All are likely to result in kin bias, because of the correlation between genetic similarity and kinship, but only some should be regarded as involving kin discrimination. 3. Non-discriminatory kin bias could arise through close relatives sharing, for instance, physical characteristics (such as those influencing competitive ability), thresholds of behavioural response or requirements for particular resources. 4. Discriminatory kin bias could arise through the direct perception of genetic similarity between individuals (direct similarity discrimination) or the use of cues likely to correlate with genetic similarity (indirect similarity discrimination--of which kin discrimination is one form). Alternatively, it could arise incidentally through mistaken identity or discrimination at some other level, such as species identification. 5. Experiments with laboratory and wild house mice have revealed kin bias in a number of contexts, including (a) parental and infanticidal behaviour, (b) sexual development and behaviour and (c) investigatory behaviour and passive body contact among juveniles and adults. 6. While kin bias in mice has been interpreted as evidence for kin discrimination, there are several problems with such an interpretation. These include (a) pronounced and complex effects of familiarity on discrimination, (b) a high risk of error-proneness in the indirect cues used in apparent kin discrimination and (c) weak and easily disrupted kin bias effects in certain contexts. 7. Consideration of social structure and discriminatory responses within populations of wild house mice leads to an alternative explanation for some kin bias in terms of incidental discrimination based on social group membership. 8. Several results from laboratory experiments suggest incidental discrimination is a more parsimonious explanation than kin discrimination for some intrasexual kin bias in behaviour. However, kin or direct similarity discrimination appears to be the most likely explanation for other aspects of intrasexual kin bias and for intersexual kin bias.

Benzodiazepine ligands, nociception and 'defeat' analgesia in male mice

Recent studies have indicated that defeat experience induces acute non-opioid analgesia in intruder mice. To investigate the potential involvement of benzodiazepine receptors in this biologically-relevant form of environmentally-induced antinociception, we initially assessed the effects of some benzodiazepine ligands on basal nociception (tail-flick assay). Chlordiazepoxide (5-30 mg/kg), midazolam (0.625-5 mg/kg), diazepam (0.5-4 mg/kg), Ro15-1788 (5-80 mg/kg) and CGS8216 (5 mg/kg) were found to be ineffective in altering basal nociception. However, higher doses of CGS8216 (10-20 mg/kg) induced significant analgesia, an effect also observed with the beta-carboline derivatives FG7142 (5-20 mg/kg) and DMCM (1-2 mg/kg). Time-course analyses revealed that the onset of CGS8216 analgesia was slower than for FG7142 and DMCM, but that all three drugs produced long-lasting elevations in tail-flick latencies. The analgesic effects of FG7142 and DMCM were completely reversed by Ro15-1788 (20 mg/kg) and by chlordiazepoxide (20 mg/kg), suggesting mediation by benzodiazepine receptor mechanisms. Although CGS8216 analgesia was also reversed by Ro15-1788, it was unaffected by chlordiazepoxide; however, diazepam (5 mg/kg) did significantly attenuate the reaction. Further studies indicated that the antinociceptive consequences of defeat experience were dose-dependently blocked by Ro15-1788 (10-40 mg/kg) and by diazepam (0.5-2 mg/kg). Surprisingly, however, neither chlordiazepoxide (5-20 mg/kg) nor midazolam (1.25-2.5 mg/kg) blocked "defeat" analgesia under present test conditions. Although several issues remain unresolved, present findings would not be inconsistent with the proposal that stimuli associated with the acute stress of defeat experience release an endogenous ligand which acts in an "inverse agonist-like" manner at benzodiazepine sites.

Resident's scent: a critical factor in acute analgesic reaction to defeat experience in male mice

Although it has recently been reported that defeated male mice evidence an acute non-opioid analgesia, little is currently known about the specific features of the defeat experience with which the analgesic reaction is associated. The present experiments not only confirm that defeat experience reliably induces acute antinociception in intruder mice, but show that a similar reaction also occurs as a consequence of exposure to an aggressive resident which does not attack during the brief test period, a well-characterized non-aggressive resident and the 'unoccupied' soiled home cage of an aggressive resident. Results also indicated that, with appropriate exposure duration, scent alone can give rise to a quantitatively similar analgesia to that observed in defeated mice. Furthermore, time-course comparisons and the absence of naloxone antagonism suggest that 'scent' and 'defeat' analgesias are mediated via a common non-opioid mechanism. Data are discussed in relation to the ecological significance of urinary odours in social communication in mice.

A possible olfactory component in the effects of diazepam on social behavior of mice

The means by which diazepam alters the social behavior of male LAC mice was investigated by analyzing 6-min dyadic social encounters between untreated, individually housed resident males and experimentally manipulated, group-housed intruders. Experiment 1 showed that at 24h and particularly 14 days after access to 0.125 mM diazepam solution, drugged intruders were attacked more when placed into a resident's home cage than were intruders receiving vehicle. After 24h, but not 14 days of treatment, drugged intruders performed fewer elements of static flight. However, on both occasions they showed proportionally less flight behavior relative to the amount of aggression residents directed towards them. In experiment 2, intruders marked with mouse urine taken from donors which had ingested the 0.125 mM diazepam solution for 24 h were attacked considerably more by residents than were intruders marked with water or normal mouse urine. Urine samples taken after 14 days of drug treatment evoked additional increases in sexual and investigatory elements in unmarked residents. The results show that, in pairs of mice, the rise in aggression associated with sustained diazepam treatment, unlike the changes in flight, arises indirectly and probably through a drug-induced change in the olfactory properties of mouse urine.

The source of an aggression-promoting olfactory cue, released by alpha-melanocyte stimulating hormone, in the male mouse

Earlier experiments demonstrated that the injection of alpha-melanocyte stimulating hormone into one mouse of a male pair results, 15 minutes later, in the release of an olfactory cue which increases the aggressive behavior of its partner. Because the preputial gland, whose activity is dependent upon testosterone and alpha-MSH, produces an odor which stimulates aggressive behavior, its relationship with the MSH response was investigated. Preputialectomy failed to prevent the release of the odor by an MSH-treated subordinate mouse of a pair, although preputialectomy of one mouse of a naive pair resulted in it later displaying higher levels of aggression than its intact partner, which then became subordinate. Swabs taken from the perineal region of alpha-MSH-injected subordinates, contained more aggression-promoting factor than swabs taken from saline injected subordinates. It is concluded that the short-term effects of alpha-MSH upon aggression are probably via a product of glandular or urinary origin other than the preputial gland and that the latter is more involved in long-term aggression-promoting cues.

Recognition fo territorial boundaries by olfactory cues in mice (Mus musculus L.)

Effects of varying olfactory cues on the behavior of domestic male mice (Mus musculus) towards territorial boundaries were studied. Territories were established by three pairs of males in a 154 X 86 X 10 cm Plexiglas pen with a moveable floor. After establishment of territories, the floor was shifted 19 cm a total of 21 times on different days. After 13 of these shifts the floor was subsequently covered with perforated sheet metal. In all 8 of the uncovered shifts, and in 8 of the 13 covered shifts, the mice behaved as though the boundary was moved in the predicted direction and distance. The results indicate that mice can use olfactory cues to recognize territorial boundaries.