Urinary Chemosignals Research Articles

Olfactory stimulation or inhibition of sexual behavior of stallions in non-breeding season

Stallions show decreased sexual responses and activities during short days in winter. To evaluate the importance of sexual olfactory communication in horses, we tested whether sexual responses could be stimulated through various sexual olfactory stimulations in winter. To this end, we presented stallions with various olfactory stimulations (urine from mares at different stages of the reproductive cycle, urine from stallions or geldings, or chemically defined synthetic odorant) during the non-breeding season and measured their behavioral responses through (1) a test of olfactory investigation (olfactory investigation and flehmen behavior) and (2) a test of sexual activity in the context of semen collection for artificial insemination. It appears that the duration of olfactory investigation and flehmen behavior is longer after presentation of urine (stallion, gelding, anestrous, diestrous and estrous mare) than after presentation of water or synthetic odorant. By contrast, geldings showed reduced flehmen behavior that did not differ from that after water presentation. It is of interest that during the mounting test, mare estrous urine was associated with significantly reduced latency to ejaculation when spread in the nostril of the stallion, compared to anestrous mare urine or water. Anestrous mare urine seems to even inhibit stallion sexual motivation as measured through a longer latency to reach mounting and ejaculation. It appears therefore that during the season of sexual rest, stallion sexual motivation can be stimulated by mare estrous urine and inhibited by mare anestrous urine. These results also suggest that the physiological state of the mare influence the content of urinary chemosignals.

Optogenetic Activation of Accessory Olfactory Bulb Input to the Forebrain Differentially Modulates Investigation of Opposite versus Same-Sex Urinary Chemosignals and Stimulates Mating in Male Mice.

Surgical or genetic disruption of vomeronasal organ (VNO)-accessory olfactory bulb (AOB) function previously eliminated the ability of male mice to processes pheromones that elicit territorial behavior and aggression. By contrast, neither disruption significantly affected mating behaviors, although VNO lesions reduced males’ investigation of nonvolatile female pheromones. We explored the contribution of VNO-AOB pheromonal processing to male courtship using optogenetic activation of AOB projections to the forebrain. Protocadherin-Cre male transgenic mice received bilateral AOB infections with channelrhodopsin2 (ChR2) viral vectors, and an optical fiber was implanted above the AOB. In olfactory choice tests, males preferred estrous female urine (EFU) over water; however, this preference was eliminated when diluted (5%) EFU was substituted for 100% EFU. Optogenetic AOB activation concurrent with nasal contact significantly augmented males’ investigation compared to 5% EFU alone. Conversely, concurrent optogenetic AOB activation significantly reduced males’ nasal investigation of diluted urine from gonadally intact males (5% IMU) compared to 5% IMU alone. These divergent effects of AOB optogenetic activation were lost when males were prevented from making direct nasal contact. Optogenetic AOB stimulation also failed to augment males’ nasal investigation of deionized water or of food odors. Finally, during mating tests, optogenetic AOB stimulation delivered for 30 s when the male was in physical contact with an estrous female significantly facilitated the occurrence of penile intromission. Our results suggest that VNO-AOB signaling differentially modifies males’ motivation to seek out female vs male urinary pheromones while augmenting males’ sexual arousal leading to intromission and improved reproductive performance.

Peripubertal exposure to male chemosignals accelerates vaginal opening and induces male-directed odor preference in female mice

Reproductive physiology in female mouse is profoundly affected by male odor. A well-known effect of male odor is the acceleration of puberty onset in prepubertal female mice exposed to male urine. Whether peripubertal exposure to male odor also influences female sexual behavior in adulthood is poorly known. Recently, we reported that female mice exposed to male-soiled bedding showed advanced vaginal opening associated with early expression of male-directed odor preference in adulthood. The aim of the present study is to determine whether peripubertal exposure to male urinary chemosignals affects both occurrence of vaginal opening and attraction to male odor at older age in female mice. Therefore, we exposed female mice to (1R, 5S, 7R)-3,4-dehydro-exo-brevicomin (DHB), 6-hydroxy-6-methyl-3-heptanone (HMH) and (S)-2-sec-butyl-4,5-dihydrothiazole (SBT), individually or in mixture, from postnatal day (PD) 21 to PD38 and monitored the occurrence of vaginal opening. We measured then the time that the female mice spent sniffing male and female mouse urinary volatiles at PD45. As expected, peripubertal exposure to DHB, HMH or SBT accelerated vaginal opening in female mice. In addition, we showed that exposure to a mixture of these three compounds induced expression of male-directed odor preference at PD45, contrary to the single exposure to each of these molecules. In conclusion, the volatile compounds DHB, HMH and SBT in urine of male mice influence both occurrence of vaginal opening and adult expression of male-directed odor preference in female mice.

Changes in volatile compounds of mouse urine as it ages: Their interactions with water and urinary proteins

Mice release a variety of chemical signals, particularly through urine, which mediate social interactions and endocrine function. Studies have been conducted to investigate the stability of urinary chemosignals in mice. Neuroendocrine and behavioral responses of mice to urine samples of male and female conspecifics which have aged for different amounts of time have been examined, demonstrating that the quality and intensity of signaling molecules in urine change over time. In this study, we monitored changes in volatile organic compounds (VOCs) released from male and female mouse urine following aging the urine samples. Substantial amounts of some VOCs were lost during the aging process of urine, whereas other VOCs increased. Considerable portions of the VOCs which exhibited the increased release were shown to have previously been dissolved in water and subsequently released as the urine dried. We also demonstrated that some VOCs decreased slightly due to their binding with the major urinary proteins (MUPs) and identified MUP ligands whose headspace concentrations increased as the urine aged. Our results underscore the important role of MUPs and the hydration status in the release of VOCs in urine, which may largely account for the changes in the quality and intensity of urinary signals over time.

Application of classification methods when group sizes are unequal by incorporation of prior probabilities to three common approaches: Application to simulations and mouse urinary chemosignals

Four common classification methods are described, Euclidean Distance to Centroids (EDC), Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA) and Support Vector Machines (SVM). In many applications of chemometrics e.g. in medicine and biology it is common for there to be unequal sample sizes in different groups. When class sizes are unequal the performance of some of these methods may be biased according to class size. This paper describes approaches for incorporating prior probabilities of class membership using Bayesian approaches to three of the methods LDA, QDA and SVM, either assuming equal probability or assuming that the relative sample sizes relate to the relative probabilities. EDC is used as a benchmark to determine model stabilities. The methods are illustrated by four simulated datasets of different structures and one real dataset consisting of the gas chromatographic profile of mouse urine comparing controls to those on a diet.

Intra‐female aggression in the mouse (Mus musculus domesticus) is linked to the estrous cycle regularity but not to ovulation

Intraspecific communication between mice takes place mainly via urinary chemosignals or "pheromones". Pheromones can influence aggressive and reproductive behavior as well as the neuroendocrine condition of the recipient female mice via their olfactory system. In this study, reproductively cyclic mice in the estrus phase were used to test intraspecific agonistic aggressive behavior. Data were obtained also on the count of the eggs shed in the oviducts. The results showed that (i) individually housed female mice are more aggressive toward an intruder female mouse than grouped mice, (ii) mice in which the vomeronasal organ was removed show aggressive behavior intermediate between individually housed and grouped mice, and (iii) a within group analysis did not show a positive correlation between aggression and presence of shed eggs in the oviducts.

Urinary chemosignals in giant pandas (Ailuropoda melanoleuca): seasonal and developmental effects on signal discrimination

AbstractAs a solitary species, giant pandas Ailuropoda melanoleuca have a chemical communication system that allows for avoidance with conspecifics throughout most of the year and facilitates breeding during their brief reproductive period. To date, most studies have focused on adults during the breeding season, but much remains to be learned about developmental and seasonal effects on chemical communication. Here, using odour discrimination methodology, we examine these contextual influences on chemosignalling in giant pandas for the first time. During the breeding season both adult and subadult giant pandas overtly discriminated conspecific sex using chemical cues in urine. Male urine was consistently investigated more than female urine by pandas across all age‐sex categories. This preference for male urine was observed for both adult and subadult urine donors, indicating that adult levels of reproductive hormones are not necessary for the production of sex‐specific urinary odour cues. By contrast, giant pandas did not overtly discriminate sex during the non‐breeding season. This finding underscores that negative results for discrimination studies need to be interpreted with caution, as many contextual factors may influence overt expression of this ability. Evidence points to seasonal changes in motivation, rather than in the availability of sex‐specific chemical cues in urine, as the causal factor for changing odour discrimination patterns. These and other findings are discussed in the light of the potential role that discrimination of odour plays in the regulation of competitive and reproductive interactions in nature.

Male urinary chemosignals differentially affect aggressive behavior in male mice.

Chemical signals modulate aggressive behavior in mice. For example, male urinary cues enhance aggression against other adults: a resident mouse attacks a male but not a castrated intruder, unless it is anointed with male urine. Our purpose was to understand whether molecules excreted with urine also act as aggression triggers in a different context. Therefore, the effect of urine, or molecules purified from urine, voided by different animals (males or females), was tested on the aggression of male mice against pups. Latency to the first attack, percentage of pups receiving the first attack, and percentage of attacked pups after 5 and 15 min were recorded. At variance with intermale aggression, male urinary chemosignals sprayed on pups reduced infanticide, while female urine did not. Male urine also delayed infanticide when compared to female urine. Pups anointed with low molecular weight dialyzed urine and with the high molecular weight protein fraction were attacked later than controls. Pups anointed with Major Urinary Proteins (MUPs) also were attacked later. The volatiles retained by MUPs act in the same way as adult male urine. MUPs and their ligands did not modify biting of food items. The results show that mice do not perceive male chemosignals as compulsory aggression triggers but rather can consistently and differentially shape their behavior in response to the same molecules according to different contextual events.

Low molecular weight constituents of male mouse urine mediate the pregnancy block effect and convey information about the identity of the mating male.

Mouse urine contains a complex mixture of chemosignals including a variety of small volatile molecules that are bound to major urinary proteins. In addition to signalling maleness, male urine also conveys information about individuality, which allows recently mated female mice to distinguish the urinary chemosignals of the mating male from those of an unfamiliar male. The highly polymorphic nature of the major urinary proteins makes them a likely candidate for conveying individuality information in the context of the pregnancy block effect. This was investigated by comparing the pregnancy-blocking effectiveness of a high molecular weight urinary fraction, containing major urinary proteins, with that of a low molecular weight fraction containing volatile ligands. Not only was the high molecular weight fraction ineffective in blocking pregnancy, but it also appeared to be less important in signalling individuality than the low molecular fraction. The high molecular weight fraction was ineffective in inducing expression of the immediate early gene product egr-1 in the accessory olfactory bulb. In contrast, the low molecular weight fraction induced egr-1 expression in the mitral/tufted neurons in the anterior subregion of the accessory olfactory bulb, suggesting that they activate the V1R class of vomeronasal receptor neuron.

Towards an understanding of the pregnancy-blocking urinary chemosignals of mice

Male mouse urine contains a pregnancy-blocking chemosignal that causes pre-implantation pregnancy failure in recently mated female mice. However, females are able to recognize the chemosignal of the male with which they mated, preventing it from aborting his own offspring. The individuality of the pregnancy-blocking chemosignal is influenced by genes of the major histocompatibility complex (MHC), although the chemical nature of the signal remains unclear. Possible candidates include fragments of MHC proteins, the highly polymorphic major urinary proteins (MUPs) and the profile of low-molecular-mass volatiles, which possess male pheromonal activity in other contexts. A recent study has found a high-molecular-mass fraction of male urine containing MUPs to be ineffective in eliciting pregnancy block. Moreover, both the pregnancy-blocking activity and the individuality of the signal were associated with the low-molecular-mass fraction of male urine.

Signal–receiver interplay in the communication of male condition by Asian elephants

Signal design and meaning are dependent on the condition of the sender and receiver as well as the response of the receiver. This study examined (1) whether female Asian elephants, Elephas maximus , can distinguish between a conspecific male in musth and nonmusth states using urinary signals, (2) how the oestrous condition of the female affects discrimination, and (3) correlation of female responses with the testosterone level of the male. Musth is a rut-like state displayed by healthy adult male elephants. Males in musth dominate nonmusth males and may be preferred by females as mates. Urine was collected from two captive male Asian elephants during nonmusth periods and from one of these males during times of musth. Samples of musth and nonmusth urine and control liquids were placed in an elephant enclosure weekly for 16 weeks, the length of a female oestrous cycle. Primary response behaviours were approach and four trunk-tip motions, namely sniff, check, place and flehmen. Musth urine consistently elicited greater responses than nonmusth and control samples. Females were more responsive during their follicular (sexually receptive) than luteal (unreceptive) stages of oestrus. Furthermore, females appeared to be sensitive to the degree of musth as responses increased with rising serum testosterone levels of the male donor. Chemical signals from males are a likely source of honest signals related to status and reproductive condition. Female elephants appear capable of detecting differences in a male based upon urinary chemosignals.

Pregnancy in female house mice exposed to urinary chemosignals from other females.

Seven experiments were performed to investigate pregnancy termination, urinary chemosignals, and litter sex ratio variation in female house mice. Experiments tested the effects of urine from adult and prepubertal females, housed individually or in groups, on successful insemination and litter production by females treated at different times and for different periods during the 3 weeks before mating and during gestation. Treatment of females with urine from adult females housed eight per cage or with urine pooled from eight adult females housed individually for 2 or 3 weeks before mating resulted in fewer successful pregnancies and significantly more female-biased litters. Treatment with urine from adult or prepubertal females housed eight per cage or with urine pooled from eight mice housed individually for the first 6 days of gestation or throughout pregnancy resulted in a significant increase in the rate of pregnancy termination. These treatments resulted in lower body weights at birth and slower growth rates in all males and in some females. Puberty was delayed in female progeny from urine-treated dams in five of seven experiments, and these young females attained first oestrus at greater mean body weights than mice in other treatments. These findings indicate that, in mice, at high population density, communication via a urinary chemosignal can alter reproduction in recipient females. Availability of, and competition for, resources such as food would be greater at higher densities, possibly lowering the probability of reproductive success. Pregnancy termination and delays in reproduction and attainment of sexual maturity might lead to greater successful reproduction at a later time.

CHEMICAL SIGNALS IN MALE HOUSE MICE URINE: PROTEIN-BOUND MOLECULES MODULATE INTERACTIONS BETWEEN SEXES

AbstractThe role of urinary chemosignals in sexual interactions was investigated in pairs of adult mice. Based on previous findings, volatile molecules bound by the Major Urinary Proteins (MUPs) from adult male urine were thought to be sufficient to carry information about the sex of the emitter, and thus sufficient to modify the behaviour of conspecifics. In the first experiment, virgin and stud adult males were exposed to receptive females painted or not with MUPs-borne molecules. Both virgin and stud males showed an increased latency to the first anogenital sniff and a reduced number of sniffings towards MUPs-treated females. This suggests that adult mice are repelled by MUPs-borne volatile molecules, even in the presence of female stimuli conveyed by receptive mates. In the second experiment only stud males were tested, with ovariectomized or estrogen-primed females. These latter were either untreated, painted with MUPs-borne molecules or MUPs without volatile ligands. Ovariectomized females and those treated with MUPs without ligands received less sniffs than the other two groups. Estrogen-primed females were mounted more times, with a shorter latency. Ovariectomized females and females treated with MUPs-borne ligands were attacked earlier by males. The presence of chemical cues from male urine is thus sufficient to modify the behaviour of stud males towards receptive females. In particular, MUPs-borne volatiles are sufficient to act as male cues and to induce aggression towards receptive females. It can be speculated that in nature adult male mice rely on olfactory cues like MUPs-borne odorants to firstly identify a male conspecific and possibly use similar chemical cues from their own urine to signal their presence.

Y Chromosome, Urinary Chemosignals, and an Agonistic Behavior (Offense) of Mice

MONAHAN, E. J. AND S. C. MAXSON. Y chromosome, urinary chemosignals, and an agonistic behavior (offense) of mice. Physiol Behav 64(2) 123–132, 1998. In mice, offense is one type of agonistic behavior associated with attacks. Offense of male mice was measured in a panel of testers design. The mice were DBA1 (D1) and DBA1.C57BL10-Y (D1.B10-Y). These are congenic for the male-specific, nonrecombining part of the Y chromosome. For the behavioral experiments, urine from D1 or D1.B10-Y mice was daubed on gonadectomized opponents. The opponents were of two genotypes, D1 or D1.B10-Y. The experimental subjects were of the same two genotypes. There were main effects for strain of experimental subject and strain of urine donor as well as interactions for strain of experimental subject × strain of gonadectomized opponent, strain of gonadectomized opponent × strain of urine donor, and strain of experimental subject × strain of gonadectomized opponent × strain of urine donor. These findings are consistent with a model in which this part of the Y chromosome affects testosterone-dependent pheromones and non-testosterone-dependent odortypes acting as motivating stimuli, the olfactory perception of motivating stimuli for offense, and the motivational mechanism for offense.

Chemosignals and activity of wild stock house mice, with a note on the use of running wheels to assess activity in rodents

Two control tests and an experimental test were used to explore the effects of urinary chemosignals on activity in house mice ( Mus domesticus). Control tests revealed that 1. (a) house mice of both sexes and different ages cling to the wheel for significant and variable proportions of their revolutions and thus correction factors must be employed to obtain useable results, and 2. (b) there is no social facilitation or inhibition of wheel running when mice are permitted to run in wheels housed near one another in the same room as opposed to being in separate rooms. Using running wheels for measurement periods of up to a week, we tested whether any of eight urinary odours or water (control) influenced activity in male and female mice that were prepubertal, pubertal, or adult. 1. (1) Prepubertal females were more active when treated with adult male urine than when treated with prepubertal male urine or water. 2. (2) Females of all three ages were generally more active when treated with urine from pregnant or lactating females when compared with the control treatment. 3. (3) Prepubertal and pubertal males were more active when treated with urine from adult males than when treated with water. 4. (4) Pubertal and adult males exhibited heightened running wheel activity when exposed to cues from oestrous, dioestrous, grouped females or prepubertal females. 5. (5) Pubertal and adult females exhibited greater activity when exposed to urine from adult males. These findings can be interpreted with regard to the physiology and behavioural biology of the mice.

MHC-associated and MHC-independent urinary chemosignals in mice

The chemosensory identity of mice, rats, and humans is determined partly by polymorphic genes of the major histocompatibility complex (MHC). In inbred strains of mice as well as in seminatural populations MHC-associated mating preferences selectively influence reproductive success. To explore MHC-associated chemosignals in relation to otherwise genetically determined chemosignals a first study was conducted on seven trained rats' responses to the odors of inbred strains of mice. Results of the first study confirmed that neither the MHC nor genes in the genetic background dominate in determining urine odor specificity of mice and that specific olfactory cues associated with either the MHC or the genetic background can be identified by olfaction. In a second study, these specific olfactory cues were analyzed by means of gas chromatography. The results indicate that specific volatile components associated with either the MHC or the genetic background can be found in mouse urine odor, and that profiles of ubiquitous volatile components show some association with either the MHC or the genetic background. Furthermore, results show that a small number of specific compounds as well as a profile of some few ubiquitous volatiles constitute MHC-associated odor cues and that influences of the MHC and genes in the genetic background interact in constituting urine odor specificity in mice.

Sexual responses to urinary chemosignals depend on photoperiod in a male primate

In male lesser mouse lemurs, testicular size and plasma testosterone levels are controlled by photoperiodic variations but can be modified by urinary cues from conspecifics. To test whether urinary cues may have differential effects on testicular size and testosterone levels depending on the photoperiodic state of the receiver, isolated males were exposed for 4 wk to urinary cues from oestrous females or dominant males:—at the beginning of the breeding season induced by long photoperiod (LD),—during refractoriness to LD leading to spontaneous sexual regression and during sexual quiescence exhibited by males kept in short photoperiod (SD). Urinary chemosignals from females were always stimulatory producing significant increases in testosterone levels. By contrast, urinary cues from dominant males produced significant differential effects on reproductive function. They depressed sexual function only at the beginning of the breeding season. During SD or during refractoriness to LD, chemosignals were stimulatory leading to increases in testosterone levels and full development of testes. These results demonstrate that the same chemosignal may have opposite effect on sexual function of the receiver depending on endocrine mechanismsset up by photoperiod.

MHC-Associated and MHC-lndependent Urinary Chemosignals in Mice Are Expressed via the Hematopoietic System

The change in genetically determined urine odors which appears after experimental bone marrow transplantations in mice was examined in order to test whether the HMC is the only group of genes that influences the chemosensory identity via the hematopoietic system. 5 female rats were trained in a computer-controlled olfactometer to discriminate urine odors of two MHC congenic or background congenic inbred strains of mice. Transfer-of-training tests with urine samples of irradiated mice which were restored with bone marrow either from an MHC congenic or a background congenic inbred strain reveal a change of urinary chemosignals after both types of experimental bone marrow transplantation. Thus, both MHC-associated as well as MHC-independent urinary chemosignals are expressed via the hematopoietic system.

Transcortical magnetic stimulation in non haemorragic stroke

Mice release a variety of chemical signals, particularly through urine, which mediate social interactions and endocrine function. Studies have been conducted to investigate the stability of urinary chemosignals in mice. Neuroendocrine and behavioral responses of mice to urine samples of male and female conspecifics which have aged for different amounts of time have been examined, demonstrating that the quality and intensity of signaling molecules in urine change over time. In this study, we monitored changes in volatile organic compounds (VOCs) released from male and female mouse urine following aging the urine samples. Substantial amounts of some VOCs were lost during the aging process of urine, whereas other VOCs increased. Considerable portions of the VOCs which exhibited the increased release were shown to have previously been dissolved in water and subsequently released as the urine dried. We also demonstrated that some VOCs decreased slightly due to their binding with the major urinary proteins (MUPs) and identified MUP ligands whose headspace concentrations increased as the urine aged. Our results underscore the important role of MUPs and the hydration status in the release of VOCs in urine, which may largely account for the changes in the quality and intensity of urinary signals over time.

The hematopoietic system influences odor specificity in mice and rats.

The change in strain-specific urine odors which appears after bone marrow transplantations was examined in mice and rats in order to demonstrate an influence of the hematopoietic system on urinary chemosignals. Four rats were trained in an olfactometer to discriminate two allogeneic mouse or rat strains via their urine odors. Urine samples obtained from two inbred strains of mice, from two inbred strains of rats, from allogeneic reconstituted mice, and from semiallogeneic reconstituted rats were combined in a number of 'transfer of training' tests. Results confirm findings that the hematopoietic system influences odor specificity in mice. For the first time a change of urinary chemosignals after bone marrow transplantation in rats was demonstrated by using semiallogeneic reconstituted rat chimeras.