Effect of vomeronasal organ removal from male mice on their preference for and neural Fos responses to female urinary odors.

Four experiments were conducted to determine whether vomeronasal organ (VNO) inputs in male mice mediate the rewarding properties of estrous female urinary odors. Sexually naive male mice with either an intact (VNOi) or lesioned (VNOx) VNO preferred to investigate female urine over water in Y-maze tests. Subsequently, VNOi males ran significantly more quickly and remained in nasal contact longer with estrous female urine than with male urine, whereas VNOx males investigated these odors equally. In home-cage habituation-dishabituation tests, VNOi males also investigated female urine significantly longer than did VNOx males, although both groups investigated female urine longer than other non-body odors. Finally, female urinary odors induced Fos in the nucleus accumbens core of VNOi males but not of VNOx males. Our results suggest that female urinary odors retain some incentive value in VNOx males. However, once direct nasal contact is made with female urine, VNO inputs further activate forebrain mechanisms that amplify the reward salience of this stimulus for the male mouse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Male mouse (Mus musculus) attraction to airborne urinary odors of conspecifics and to food odors: Effects of food deprivation.

Five experiments demonstrated that 112 male mice were strongly attracted to the urinary odors of females, and that male urinary odors were considerably less attractive. The strong attraction to female urinary odors did not require that the males have postweaning experience with females. Males with continuous access to food and water were much more strongly attracted to female urinary odors than to the airborne food odors. Female urinary odors remained more attractive than food odors after 24-hr food deprivation, and only after 48-hr deprivation did the attractiveness of food odors approximate that of female urine. Although 48-hr food deprivation appeared to equalize the attractiveness of urinary and food odors, this regimen did so not by diminishing the attractiveness of female urine but rather by increasing the attractiveness of food odors. It is argued that the attraction that male mice exhibited to female urinary odors in this odor-testing apparatus reflected, at least in part, a biologically important precopulatory communication system. (29 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Preputial glands of infant rats (Rattus norvegicus) provide chemosignals for maternal discrimination of sex.

In 4 experiments, dams were presented with simultaneous choice tests of pup odors, and their investigatory sniffing was measured. Dams did not show differential sniffing of male and female bladder urine or urine voided by pups with preputial glands removed (PPX). They preferred urine voided by intact male pups to that voided by intact females, and they preferred urine voided by intact pups to that of PPX pups within each sex. Finally, they preferred water homogenates of preputial glands removed from male pups to those of female pups. It is concluded that the neonatal preputial gland is a source of chemosignals that are attractive to dams and that are used by dams to identify sex of pup. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultrasonic vocalizations by male house mice (Mus musculus) to novel odors: Roles of infant and adult experience.

Conducted 2 experiments to examine 70-kHz ultrasonic courtship vocalizations by adult male mice to novel odors following exposure to these odors in infancy and/or adulthood. Exp I, with 72 males, demonstrated that adult males normally do not vocalize to the urine of female rats but would if adult female mice odorized with female rat urine were repeatedly encountered postpubertally. On the other hand, encountering their own mother odorized with female rat urine from birth until weaning did not promote vocalizations to the urine of female rats. Exp II, with 100 males, examined vocalizations to the urine of female mice whose urinary odor was altered by the ingestion of fenugreek, a spice. Greater amounts of vocalization again were seen by males that as adults encountered females that had ingested fenugreek. Again, experience with the novel odor during infancy was not associated with elevated vocalizations during adulthood either to fenugreek-altered urine or to the fenugreek odor itself. Vocalizations to 2 different novel odors occurred only after an adult male had encountered an adult female odorized with the novel odor. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in urinary odors produced by young laboratory rats (Rattus norvegicus).

Examined the responses of 75 primiparous Long-Evans rat dams and 20 nonmaternal Long-Evans females to male and female pup urine in 3 experiments. Investigatory sniffing of male and female pup urine deposits by maternal Ss was compared in a series of simultaneous choice tests given at 3-day intervals between Day 2 and Day 17 postpartum. Male urine was consistently preferred. Introduction of male but not female pup urine to the nest was found to significantly elevate maternal licking of anogenital regions of pups. Thus, urine from pups of various ages contains sex-identifying odors that differentially elicit spontaneous maternal interest. The odor of male urine may provide a sufficient stimulus to account for the greater anogenital licking that males of this species normally receive. Nonmaternal, naive, adult Ss behaved like maternal Ss, preferring male urine in the choice test, which indicates that the maternal condition of a dam is not necessary either for the olfactory discrimination or for the male odor preference. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odor preferences of female house mice (Mus domesticus) in seminatural enclosures.

Preferences for male odors by female house mice (Mus domesticus) were examined with respect to age, dominance status, and spatial relationships. Mice were free living in 6 field enclosures. Estrous or nonestrous females were placed in an aquarium with soiled bedding from live traps as the odor source. Females were tested for preferences between (1) adult and juvenile male odors, (2) dominant and subordinate male odors, and (3) "near" and "far" male odors. In dominance odor tests, estrous females preferred odors from dominant males; nonestrous females exhibited no significant preferences. In adult juvenile and spatial odor tests, there were no significant differences between odor preferences of estrous and nonestrous females. However, most females preferred odors from adult and "near" males. Male dominance status appears to be the strongest influence on female odor preference in these seminatural enclosures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causes of scent marking in female golden hamsters (Mesocricetus auratus): Specific signals or classes of information?

Odor-elicited scent marking is common among mammals, but the proximate causes of marking are not well understood. Scent marking by female hamsters in response to 8 different male odors was investigated. Two odors (flank, mouth) increased flank marking and 2 (flank, rump) increased vaginal marking; in the latter case the effects of flank and rump odors were additive. Two odors (feces, urine) decreased flank marking but did not affect vaginal marking; other odors (foot, ear, ano-genital) had no influence on either scent-marking behavior. Results show that scent marking by females is influenced by a limited number of male odors, suggesting specific effects of particular odors. Classes of information (such as sexual identity) were not relevant causes of scent marking, as some odors containing such information were effective but others were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexually dimorphic enhancement by estradiol of male urinary odor detection thresholds in mice.

We asked whether sex and adult estrogen exposure influence the detection thresholds for urinary odors used by mice to guide their social behaviors. Gonadectomized (GDX) male and female mice were trained on a two-choice food-motivated task to determine detection thresholds for male urinary odors. There was no significant sex difference in the detection of these odors by GDX subjects without hormone replacement. However, during treatment with estradiol benzoate (EB), GDX females, but not GDX males, showed an enhanced ability to detect these odors. To investigate a possible mechanism for this effect, the authors measured GDX females' odor-sampling behavior (sniffing) by monitoring intranasal pressure transients during performance of the urinary odor detection task with and without EB treatment. Under both hormone conditions, females decreased their sniffing frequency as the urinary odor concentration decreased, with this decrease being significantly greater while GDX females received EB. Thus, estradiol enhanced detection thresholds for male urine in a sex-specific manner, and this enhanced sensitivity in females was correlated with altered odor-sampling behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of response to urine odor as a consequence of vomeronasal organ removal in male guinea pigs.

The present authors (see record 1983-12216-001) previously showed that, over time, removal of the vomeronasal chemoreceptor organ (VNO) in male guinea pigs disrupted investigatory responses to conspecific odors. The present study, with 24 Ss, investigated whether this result reflected sequelae to surgical trauma or an extinction of the response due to lack of reinforcement. The VNO was surgically removed in 2 groups of Ss (A and B), and a 3rd group (C) experienced sham surgery. Beginning 3 wks following surgery, Ss in Groups A and C were given 2 standard urine-response tests/week for 24 wks. Initiation of testing of Group B Ss was delayed until Week 15 following surgery. Results indicate that (a) responses of Group A declined relative to those of Group C; (b) at the 1st postsurgical test, Group B was as responsive to urine as Group C and much more responsive than Group A; and (c) a decline in responses for Group B occurred during tests after Week 15. Data strongly support the extinction hypothesis. It is concluded that although the main olfactory system is capable of eliciting a high level of investigatory behavior in response to female urine odors, this response wanes in the absence of the VNO, perhaps due to a loss of reinforcing properties associated with VNO stimulation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Histochemical localization of adenylate cyclase in cultured sympathetic neurons

The influence of female odors on agonistic behavior among grouped male prairie voles (Microtus ochrogaster) was studied. After the introduction of female odors, investigative behavioral interactions between the males increased in frequency. The source of the odor, the sexual experience of the males, and the ongoing behavior of the group influenced the intensity of the behavioral response. Sexually experienced males showed the greatest number of agonistic instances and attempted sexual interactions after the introduction of urine from estrous females. Agonistic interactions did not decrease upon the introduction of female odors, as has been reported for Mus musculus. It is concluded that these behavioral changes are not due to a response to a releaser pheromone, but are the result of confusion in communication between males.     

Role of frontal cortex in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Orbital/agranular insular (ORB/AI) cortex has been implicated in traditional olfactory learning tasks and social behavior but its precise role in discriminating-learning social odors is not known. Female golden hamsters received aspiration lesions of ORB/AI or dorsomedial (DM) frontal cortex and were tested for their ability to (a) discriminate between odors of individual males in a habituation-discrimination task, (b) show preferences for male over female odors, and (c) scent-mark in response to male odors. Lesioned females readily discriminated between scents of individual males. Neither lesion altered female preferences for male odors. Females with DM lesions showed increased levels of scent marking to male odors, but those with ORB/AI cortex lesions did not differ from controls. Thus, ORB/AI cortex does not appear to be critical for discrimination of odors of individuals or sex or for scent-marking responses based on these discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions centered on the medial amygdala impair scent-marking and sex-odor recognition but spare discrimination of individual odors in female golden hamsters.

The medial amygdala (Me) has been implicated in various social behaviors that depend on chemosensory cues, but its precise role in discriminating and learning social odors is not known. Female golden hamsters (Mesocricetus auratus) received electrolytic lesions of the Me or sham surgery and were tested for their ability to (a) discriminate between odors of individual males in a habituation–discrimination task, (b) show preferences for male over female odors in a Y maze, and (c) scent-mark in response to male and female odors. All females discriminated between scents of individual males. In contrast, Me lesions eliminated female preferences for male odors in a Y maze. Females with Me lesions also showed a substantial reduction in vaginal marking and virtually no flank marking in response to odors. Thus, the Me in female hamsters is critical for differential investigation of opposite-sex odors and for scent-marking behavior but is not involved in discrimination between odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactions of deer mice (Peromyscus maniculatus) and white-footed mice (Peromyscus leucopus) to homospecific and heterospecific urine odors.

Examined approach and withdrawal behaviors to homospecific and heterospecific urine odors in 2 experiments with 64 sexually naive mice from sympatric populations of Peromyscus maniculatus and Peromyscus leucopus. In Exp I, P. maniculatus females preferred homospecific male urine odor to air during both estrus and diestrus, and air to P. leucopus male urine odor under comparable conditions. P. leucopus females did not show similarly consistent behavior in the presence of these stimuli. In Exp. II, 32 P. leucopus Ss avoided male urine odors of both species, whereas 32 P. maniculatus Ss showed neither attraction nor avoidance to these odors. Results suggest urine might be used by P. maniculatus, but probably not by P. leucopus, for intra- and interspecific communication. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modification of Odor Investigation and Discrimination in Female Opossums (Monodelphis domestica) Following the Ablation of the Accessory Olfactory Bulbs.

To determine whether the vomeronasal system of the Brazilian short-tailed opossum (Monodelphis domestica) is important to the response to conspecific chemical signals, the authors tested female opossums with conspecific odors, before and after ablation of their accessory olfactory bulbs (AOBs). Anesthesia and sham treatments did not modify females' discrimination of conspecific odors when tested against water, between male and female odors, or between different odors from the same male donors. Odor investigation was partially diminished following partial ablation of the AOB, and complete ablation of the AOBs further impaired the ability of females to discriminate between certain odors. These findings provide the first evidence for the importance of the vomeronasal system in the detection of chemosignals of known origin in opossums. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the hippocampal system in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Female golden hamsters (Mesocricetus auratus) received aspiration lesions of the parahippocampal region (PARA) or electrolytic lesions of the fimbria-fornix (FNX) and were tested for their (a) discrimination between odors of individual males in a habituation-discrimination task, (b) preference for male over female odors, and (c) scent-marking in response to conspecific odors. Both lesion groups habituated to repeated presentations of a male's odor. However, only FNX females discriminated between scents of individual males, whereas PARA females did not. Neither lesion eliminated female preferences for male odors. Females with FNX lesions showed decreased levels of scent marking, but those with PARA lesions had more subtle deficits. Thus, the PARA, but not the subcortical connections of the hippocampus, is critical for discrimination of the odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial amygdala involvement in discrimination of same-species and closely-related-species male stimuli in estrous female Mesocricetus hamsters.

Efficient discrimination between individuals of closely related species is important to maximize reproductive potential. Some studies using males as subjects have indicated that the medial amygdala (MeA) is involved in discrimination between odors of conspecific females and females from distantly related species. The authors investigated the involvement of the MeA in discrimination by females between odors of conspecific males and odors of males of a closely related species. The authors exposed estrous or diestrous female hamsters (Mesocricetus auratus) to saline, conspecific male odors, or heterospecific (M. brandti) male odors and quantified the expression of c-fos–related antigens in the anterior and posterior MeA. They found that estrous (but not diestrous) females investigated conspecific male odors longer than heterospecific male odors. Neural activity in both the anterior and the posterior MeA was higher in estrous than in diestrous females. In the anterior MeA, there were no significant differences in response to odors of conspecific and heterospecific males. In the posterior MeA, however, neural activity was higher when estrous females were exposed to conspecific odors than when they were exposed to heterospecific odors. No such difference was observed in diestrous females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimuli for male mouse (Mus musculus) ultrasonic courtship vocalizations: Presence of female chemosignals and/or absence of male chemosignals.

In research on animal chemocommunication, biological odors are sometimes presented by being applied to a "neutral" animal (e.g., castrated or ovariectomized conspecific). This technique is typically utilized when the behavioral response to the odor requires the presence of a conspecific. In 5 experiments, DBA/2J and 2 F? hybrid strains of mice that might be expected to be neutral stimuli were examined for their abilities to elicit ultrasonic courtship vocalizations from male mice. Paradoxically, adult castrated males, adult males that were neonatally castrated, hypophysectomized males, prepubertal females, and hypophysectomized females all elicited more vocalizations than would have been predicted from previous research in which their urine alone was used as the stimulus. These and previous results are consistent with courtship vocalizations being promoted by chemosignals from females and/or by an absence of cues from males. Thus, a truly neutral conspecific for presenting female sex odors may not exist in mice. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual behavior increases dopamine transmission in the nucleus accumbens and striatum of male rats: Comparison with novelty and locomotion.

Extracellular concentrations of dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were examined concurrently, using in vivo microdialysis, in the nucleus accumbens and dorsal striatum of sexually active male rats during tests of locomotor activity, exposure to a novel chamber, exposure to sex odors, the presentation of a sexually receptive female, and copulation. DA increased significantly in the nucleus accumbens when the males were presented with a sexually receptive female behind a screen and increased further during copulation. Although DA also increased significantly in the dorsal striatum during copulation, the magnitude of the effect was significantly lower than that observed in the nucleus accumbens. In contrast, forced locomotion on a rotating drum, exposure to a novel chamber, and exposure to sex odors did not increase DA significantly in either region. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Communication among hamsters by high-frequency acoustic signals: II. Determinants of calling by females and males.

A previous study by the authors (see record 1978-09410-001) showed that basal rates of high-frequency vocalization by estrous female hamsters exceeded those typical of nonestrous females. In the present 6 studies with random-bred (Lak:LVG) hamsters, even higher rates of calling by estrous females were provoked by male odors (male shavings or anesthetized males). This suggested that cues which normally indicate a male's proximity can increase the rate of high-frequency calls by an estrous female. These findings are consistent with a view of female "ultrasounds" as sexual advertisements which indicate the locations, sexual receptivity, and relative passivity of estrous females to nearby male conspecifies. Male hamsters also produced ultrasounds at rates that seemed to depend on the availability of potential males. Brief exposure to an awake female stimulated male calling; however, estrous females provoked higher call rates than did nonestrous females. Exposure to anesthetized females also increased the rate of male calling, which suggests that the stimulation of male calling by awake females depends in part on female odors. These results suggest that both male and female ultrasounds are parts of a communication system that facilitates reproduction by helping to coordinate social behavior with endocrine state. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of olfactory stimuli during copulation in male and female rats.

Describes 3 experiments with a total of 74 gonadally-normal male and 29 ovariectomized female Long-Evans rats. Male and female reactions toward odors from novel and original partners were observed prior to the male's attaining his 1st or 2nd ejaculation. The male's reaction depended upon the sexual condition of the female. Only prior to their initial ejaculation did the males prefer their original partner's odors to those of novel females and only if the odors were collected from the females prior to copulation. This finding corresponded with observations of the male's random choice of partner during copulation. Females responded nonpreferentially if they had copulated prior to testing and showed a marked decrease in responsiveness as copulation continued. Prior to copulation females preferred the odors from males which had not copulated to those of males which had. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)