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)     

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)     

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)     

The role of vaginal secretion in hamster sexual behavior: Males' responses to normal and vaginectomized females and their odors.

Two experiments (with 60 adult male hamsters and 4 sexually naive male hamsters) examined the importance of vaginal secretion relative to other feminine odors for attraction of males and elicitation of copulatory behavior by comparing the behavior of males toward normal females with that toward vaginectomized Ss. Males were more attracted to intact females than to vaginectomized Ss when odors were the only cues available and also when auditory, visual, and odor cues were available but contact was prevented. There were no differences in the attractiveness of estrous and diestrous Ss whether intact or vaginectomized. When males and females were allowed to interact, there were no differences in any measures of male sexual behavior toward normal vs vaginectomized females, which indicates that the presence of vaginal secretion is not necessary for male sexual behavior. The significance for conceptions of pheromone action in mammals is discussed. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attraction to odors in hamsters: An evaluation of methods.

In Exp I with 72 male hamsters, Ss were presented with 6 attraction tasks. In 5 of the 6 tasks, one stimulus (vaginal secretion) was sniffed longer than any other stimulus. However, the degree of difference between this stimulus and the others and the relative attractiveness or aversiveness of the other stimuli varied greatly across methods. When 50 female hamsters were presented with 5 preference tasks in Exp II, Ss demonstrated a significant preference for the odors of intact males over those of castrated males in 4 of the 5 methods. It is suggested that preference tasks were more sensitive and less variable due to details of the method employed than were attraction tasks. Procedures that used S's own home cage as the testing environment tended to emphasize effects due to novelty rather than the inherent attractiveness of the odorants. Thus, use of novel objects as sources for test odors and use of airstreams for delivery of odors reduced the salience of test odorants. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intermale fighting affected by home-cage odors of male and female mice.

Conducted 3 experiments to test the hypothesis that male mice can produce an aggression-inhibitory or facilitory odor under varying conditions of social stimulation. In Exp I, 25 male fighter mice fought 25 castrated opponents more vigorously in soiled home cages of either single or stable groups of male mice than they did in clean cages. Fighting was also stimulated in cages briefly occupied by other pairs of fighting mice. It is concluded that the release of aggression-promoting home-cage odors by male mice is not necessarily a consequence of social instability and that they are of urinary, rather than preputial, origin. In Exp II (with 21 fresh Ss) and Exp. III (with 30 Ss from Exp I), odors deposited by either single or groups of female mice greatly reduced fighting, indicating that their urinary aggression-inhibiting pheromone is effective after deposition upon the home environment. Testosterone propionate implants abolished the females' inhibitory pheromone and did so independently of their enlarged preputial glands. (20 ref) (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)     

Odor preference and urine-marking scales in male and female rats: Effects of gonadectomy and sexual experience on responses to conspecific odors.

Investigation and urine-marking responses of 112 male and female Long-Evans rats toward conspecific urine odors were recorded in pair-wise comparison tests. Each of 16 S groups was given 15 preference tests, 1 for each of the possible pairs of 5 urine odors and a no-odor control (N). The urine sources were own group (G), intact male (M), castrated male (Mc), ovariectomized female (Fo), and estrous females (F). Results were scaled by using a technique based on L. L. Thurstone's (1927) law of comparative judgment. Intact males with sexual experience ordered their odor preferences N?     

Analgesic responses of male mice exposed to the odors of parasitized females: Effects of male sexual experience and infection status.

The present study shows that parasites influence both the responses of males to infected females and the responses of male hosts to females. Male mice exposed for 30 min to the odors of females infected with the nematode parasite Heligmosomoides polygyrus displayed a naloxone-sensitive, opioid-mediated analgesia, whereas males exposed for 1 min showed a shorter duration and lower amplitude naloxone-insensitive "nonopioid" analgesia that involved serotoninergic (5-HT) and excitatory amino acid (N-methyl-D-aspartate [NMDA] receptor) systems. The male mice distinguished between the odors of infected and physically stressed females, displaying greater analgesia after exposure to the odors of infected than stressed females. The analgesic responses to the odors of infected females were also affected by the males' prior sexual experience; sexually experienced males exhibited significantly greater analgesia than sexually naive males. In contrast, male mice infected with H. polygyrus failed to show a nonopioid analgesia after exposure to the odors of infected females and displayed a markedly lower level of opioid analgesia than uninfected mice. These results show that male mice can discriminate between the odors of parasitized and nonparasitized females… (PsycINFO Database Record (c) 2010 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)     

Dietary self-selection of golden hamsters in response to acute food deprivation and chronic food restriction.

Adult male golden hamsters were maintained on either Purina Rat Chow (Chow diet) or a self-selection diet consisting of high-protein chow, pure fat, and pure carbohydrate (Choice diet). In Experiment 1, animals were deprived of food for single periods of up to 48 hr. Animals on the Chow diet did not increase intake at any time after deprivation; animals on the Choice diet selectively increased their consumption of fat-derived calories and increased their total caloric intake during the first 6 hr of refeeding, but not thereafter. The nature of the diet did not influence the rate at which animals regained weight following deprivation. In Experiment 2, hamsters were placed on food-restriction schedules (access to food either for 1 hr/day only or on alternate days only) until they lost 20% of starting body weight. Chow-fed animals demonstrated little or no change in food intake either during or after food restriction. Hamsters on the Choice diet consumed more calories and lost weight more slowly than did chow-fed animals during 1-hr/day feeding; intake of fat-derived calories was elevated during restriction. Choice hamsters increased total caloric intake only towards the end of the alternate-days restriction schedule. Choice hamsters were hyperphagic following both types of food-restriction schedules, but no increased preference for fat-derived calories was observed. Factors influencing food consumption of hamsters in response to deprivation and restriction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reaction of male Mongolian gerbils to odors in a social situation.

Examined the possibility that odor from substances rubbed on the back of young stimulus animals will influence the social behavior of male gerbils. 30 adult Ss were tested for 4 5-min sessions with young male conspecifics that had water, perfume, urine, or ventral gland sebum rubbed on their back. Ss showed significantly longer investigation duration and higher approach frequencies toward Ss treated with urine or sebum. Results demonstrate that gerbils are attracted to relevant odors in a social situation. (18 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)     

Responses of male hamsters to odors of females in different reproductive states.

Six experiments investigated the responses of male hamsters to the odors of estrous, diestrous, pregnant, and lactating hamsters. Scent-marking by males in the soiled cages of females was less frequent when the females were estrous (Day 1 of the cycle) than when females were on Days 2, 3, or 4. Sexually experienced males preferred the odors of bedding material from the cages of estrous Ss over odors of bedding of diestrous Ss. Both of these effects were eliminated by surgically removing the vagina and thereby eliminating vaginal secretions. The quantity of vaginal secretions deposited in the vicinity of the nest may be responsible for the observed effects. In contrast, neither males with sexual experience nor males with both sexual and nonsexual experience with females demonstrated preferences for the odors of the estrous or diestrous Ss themselves. Males were, however, more attracted to the odors emanating directly from estrous Ss than to the odors of pregnant or lactating Ss. For hamsters the important sexual message may be not "estrous" vs "diestrous" but rather may be "will soon be estrous" (i.e., cycling) vs "not soon estrous" (i.e., pregnant, lactating, or acyclic). (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative studies of social behavior in Callicebus and Saimiri: strength and specificity of attraction between male-female cagemates

The strength and specificity of attraction between male and female cagemates was compared in Saimiri and Callicebus, using paired-comparison and single-stimulus methods of testing. Results from both methods showed that the attraction to the cagemate was stronger and more specific in Callicebus than in Saimiri. Sex differences were more pronounced in Saimiri than in Callicebus. Squirrel monkey females were more strongly attracted to strangers than were males and they clearly preferred female strangers over male strangers or their male cagemates.     

The paternally expressed gene Peg3 regulates sexual experience-dependent preferences for estrous odors.

Sexual experience has marked and long-lasting effects on male behavior in mammals, regulating traits such as the anticipation and display of sexual behavior, aggression, and olfaction. The authors conducted urine preference, habituation-dishabituation, and partner choice tests with sexually experienced and naive male mice and found that wild-type males acquire adaptively significant preferences for the odors of receptive, estrous females with sexual experience, and that these preferences are matched by changes in main olfactory system responses involving the piriform cortex, as indicated by c-Fos expression. The authors also report that these experiential effects are disrupted in male mice carrying a knockout of the imprinted gene Peg3. This paternally expressed gene regulates maternal care and offspring development, but the authors here report that Peg3 mutant males suffer a complex olfactory deficit that affects estrous odor preferences and the responses of the main olfactory system to such odors. Peg3 appears to have evolved to regulate the experience-dependent preference for receptive females, an adaptive trait that would enhance male reproductive success and so potentially increase paternal transmission of this paternally expressed gene. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term contact elicits heterospecific behavior discrimination of individual odors in mound-building mice (Mus spicilegus).

The authors used a habituation-dishabituation procedure to test the ability of male mound-building mice (Mus spicilegus) to discriminate individual odors from males of another species of mouse. Male mound-building mice failed to spontaneously discriminate individual odors from Mus musculus musculus males, a natural competitor. After 24-hr contact with a male of one of the M. musculus subspecies (M. m. musculus or M. m. domesticus), experienced M. spicilegus males discriminated the individual odors of unfamiliar males of the same subspecies. These results confirm that discrimination of individual chemosignals is not confined to olfactory cues of a single species and provide new information about the effect of short-term contact on discrimination of individual odors across species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences and residual effects of food deprivation in the satiated rat.

Following 100 days of food deprivation, during which 9 male and 9 female albino rats received acquisition and extinction training in a runway, and following 2 mo of ad lib feeding, Ss were given a reacquisition test under satiated conditions. Results indicate that females were significantly superior in running speed and frequency of food consumption during satiated reacquisition; while there was a large performance decrement in males following the drive shift, females performed at about the same level during satiation as during food deprivation. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses of male Mongolian gerbils to male gerbil odors.

Offered adult male Mongolian gerbils (Meriones unguiculatus). the opportunity to enter and investigate several combinations of male gerbil-inhabited and uninhabited areas in a 2-choice preference apparatus. Responses of 12 normal, 10 bulbectomized, 10 enucleated, and 9 castrated Ss indicate that: (a) males prefer to investigate areas containing self-generated or conspecific-generated biological odors over areas containing no gerbil odors; (b) although entry and investigation time scores probably reflect different aspects of orientation to biological odors, both measures suggest that the complex of odors generated by males is attractive to male conspecifics; (c) the odors mediating preferences are dependent primarily but not exclusively on testicular androgen; and (d) preference for normal conspecific odors is not dependent on circulating testicular androgen in the responding S. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enrichment to odors improves olfactory discrimination in adult rats.

The authors tested how prior odor enrichment affects the spontaneous discrimination of both preexposed and novel odors. Experimental rats were exposed to single odors or to pairs of similar or dissimilar odors for 1-hr periods twice daily over 20 days. Spontaneous discriminations between pairs of similar odors were tested before and after the odor exposure period using an olfactory habituation task. The authors found that (a) experimental rats did not spontaneously discriminate similar odor pairs before the exposure period, whereas they spontaneously discriminated them after the enrichment period, and (b) the improvement of performance was not selective for the odors used during enrichment. These results show that odor experience changes perception in the manner predicted based on other groups' electrophysiological experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)