Social play soliciting by male and female juvenile rats: Effects of neonatal androgenization and sex of cagemates.

Investigated the behavior of male and female Long-Evans hooded rats during individual exposure to nonplayful juvenile social stimuli in a novel test of play-soliciting behavior in 2 experiments examining hormonal and experiential determinants of sex differences. In Exp I, using 36 female and 18 male Ss, neonatally androgenized females engaged in play soliciting at a level equal to that of male controls and greater than that of nonandrogenized female controls. In Exp II, 52 males and 32 females were reared in unisexual and bisexual groups in order to compare long-term sex-related social experience effects on juvenile play soliciting. Males exposed only to other young males engaged in greater play soliciting than males exposed to both sexes; females, in contrast, were unaffected by sex of cagemates. Within rearing conditions, however, males engaged in greater play soliciting than females. The combined results suggest that perinatal gonadal androgen exposure effects on social play are prepotent and contribute essentially to sex differences in the initiation of social play behavior. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A kinematic analysis of evasive dodging movements used during food protection in the rat (Rattus norvegicus): Evidence for sex differences in movement.

Food-deprived rats (Rattus norvegicus) will protect their food by dodging away from a conspecific. A detailed kinematic analysis of these movements in adult rats shows that each sex uses sex-typical movements. Females move their snout through a greater spatial curvature, and their snout achieves a greater velocity, relative to the pelvis, than males. Males make more hindpaw steps than females and achieve a more simultaneous movement of the fore- and hindquarters. This suggests that females pivot around a point more posterior on the body than males. The finding that functionally similar patterns of movement have a sex-specific organization provides a new dimension for the study of sex differences. These differences are discussed in relation to sex differences in sex-typical behaviors, associated body structure, and neural control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of estrogens and antiestrogens in a rat model for hot flush

A potent convulsant, trimethylolpropane phosphate (TMPP), was evaluated for long-term effects on measures of social behaviors and anxiety in Long-Evans rats. Animals received three to four daily treatments of TMPP (0.1 mg/kg/ml) beginning at age 23 days in Experiment 1 and 73 days in Experiment 2. Gregariousness was measured in juvenile play and adult social investigation. Anxiousness was measured in the open field and elevated plus-maze. Long-lasting changes in social behaviors were found: play and social investigation were elevated, especially in female rats. Also, an aversive environmental experience associated with TMPP treatment influenced the drug effect on social investigation for males, but not females. In males, TMPP- vs. VEH-treated animals displayed greater social investigation when the treatment was in a positive environment than in an aversive one. In contrast, TMPP- vs. VEH-treated females showed greater social investigation regardless of environmental experience. There were no treatment group differences for measures of anxiety. These results suggest short-term exposure to TMPP may lead to long-lasting changes in specific social behaviors and neural substrates related to them, but not to changes in anxiousness.     

Alcohol exposure during development alters hypothalamic neurotransmitter concentrations

The effect of exposure to alcohol during a period roughly equivalent to the human third trimester on neurotransmitter content in the rat hypothalamus was examined. The alcohol exposure was accomplished via an artificial rearing procedure. The alcohol group was exposed to 5 g/kg/day of ethanol from postnatal day (PD) 4 to 10. There was an artificially reared control group not exposed to alcohol and a normally reared control group. Noradrenaline, dopamine, homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were measured using high performance liquid chromatography with electrochemical detection in juvenile and adult rats. There were no effects in juvenile rats. In adult rats, alcohol exposure from PD 4 to 10 increased hypothalamic content of noradrenaline, dopamine, serotonin and 5-HIAA. While adult females had greater amounts of hypothalamic serotonin and 5-HIAA than adult males, there were no interactions of sex with alcohol exposure. These results suggest that hypothalamic function is seriously disrupted by alcohol exposure during development.     

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)     

Social chemosignals in five Belontiidae (Pisces) species.

Examined approach behaviors toward conspecific chemical stimuli of the opposite sex in 5 Belontiidae species: Betta splendens, Macropodus opercularis, Colisa labiosa, C. lalia, and Trichogaster trichopterus. Approach was measured by (a) preference for Section 1 of a 3-section tank, which contained a vertical tube that introduced the stimulus water, and (b) occupancy of the tube. Exps IA and IB showed that (a) approach behaviors were displayed by the isolated male Betta only to ripe-female stimulus water, (b) group-housed males of the remaining 4 species were not attracted to female-conditioned water, and (c) socially isolated males of these 4 species preferred Section 1 during presentation of either ripe- or nonripe-female-inhabited water but occupied the tube only during exposure to ripe-female-conditioned water. The findings of Exp IIA were that (a) the female Betta, regardless of physiological state, showed approach behaviors to male-inhabited water and (b) only ripe females of the remaining species indicated a preference for Section 1 during male-water exposure but performed no tube entries. Results of Exp IIB indicate that social isolation of the females, especially ripe females, facilitated their approach behaviors. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female Japanese quail (Coturnix japonica) mated with males that harassed them are unlikely to lay fertilized eggs.

Results of previous studies of courtship and mating in Japanese quail (Coturnix japonica) suggest that females avoid conspecific males because, while courting and mating, males engage in behaviors that are potentially injurious to females. However, prior experiments provided no direct evidence that females avoided harassing males. Here the authors show that a female quail choosing between a previous sex partner and an unfamiliar male avoids the former if he engaged in relatively many potentially injurious acts while courting and mating, (Experiments 1 and 2) and that males behaving aggressively toward mates are less likely than are gentler males to fertilize the females' eggs (Experiment 3). Male sexual harassment appears to be a tactic both aversive to female quail and relatively ineffective in fertilizing them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of maternal behavior in nulliparous rats (Rattus norvegicus): Effects of sex and early maternal experience.

72 weanling female and male CD rats were exposed to either pups or pup-sized toys for 10 days beginning at 22 days of age in order to assess differences between pup-directed and toy-directed behaviors and to determine whether exposure to pups at this time increases susceptibility to maternal sensitization in adulthood. Adult sensitization involved exposing each S to pups for 10 days beginning at 78 days of age. Weanlings retrieved, licked, and lay over pups but not toys, and chewed on toys but not pups. Weanling males showed more pup retrieval than weanling females. Females and males preexposed to pups showed more retrieval and licking of pups in adulthood than those not preexposed to pups. Adult females were more fully maternal or nonmaternal than were adult males or weanlings of either sex, as indicated by their lower "partial retrieval" and "inconsistent retrieval" scores, their tendency to retrieve rapidly or not at all, and the greater correlation between their retrieval and nest construction. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of castration on grooming in goats

In African antelope and North American cervids, breeding males during the rut engage in less oral self-grooming, and harbor a greater density of ticks, compared with conspecific females and non-breeding males. The purpose of this study was to experimentally test the proposition that down-regulation of self grooming in some male bovids occurs via the direct or indirect action of testosterone. Domestic dairy goats (Capra hircus) were used as a model. In Experiment 1, comparative observations conducted on twelve gonadally intact male goats (bucks), nine males castrated at 3 weeks of age (wethers), and twelve intact females (does) supported the prediction that the grooming rate of intact males would be depressed relative to wethers and does. Bucks oral groomed at one-third and one-fourth the rate of wethers and does, respectively, and they scratch groomed half as much as does. There was no significant difference between wethers and does in oral or scratch grooming rates. Experiment 2 involved castration of eleven bucks from Experiment 1, followed by 2 months of observation. Similar to the pattern of other testosterone-dependent behavioral changes after castration in adult males, there was a good deal of variation in the individual grooming response of males to castration, with increases in grooming taking 2 to 8 weeks to be manifested in ten of eleven goats. Overall, castrated males oral groomed about 3 x above their intact rates, supporting the prediction that castration removes testosterone-mediated suppression of grooming. This is the first example of alteration of grooming behavior in males by gonadal androgen, and the first demonstration of enhancement of any mammalian behavior by removal of gonadal androgen.     

Social malleability in cowbirds (Molothrus ater artemisiae): Species and mate recognition in the first 2 years of life.

In a longitudinal study, the authors housed wild-caught juvenile male cowbirds (Molothrus ater artemisiae) with female cowbirds or canaries (Serinus canaria) from August until May. The males were then exposed to 3 social contexts. Males housed with canaries directed more vocalizations to canaries than to female cowbirds. Males housed with female cowbirds vocalized most to other males. The data revealed plasticity at a rudimentary level of reproductive behavior, selective responding to members of one's own species. Song potency, as assayed by playback, did not predict vocal use. To test adult malleability, the authors studied the males for a 2nd yr. Half were housed with conspecific females and experienced males and half with only females. The manipulation eradicated any signs of the males' 1st-yr experiences. The data suggest malleability in species and mate recognition in cowbirds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social olfaction in male brown lemmings (Lemmus sibiricus?=?trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): I. Discrimination of species, sex, and estrous condition.

Five experiments were conducted with 196 collared and 243 brown male lemmings. When tested in a Y-maze olfactometer, sexually experienced and naive Ss of both species preferred the odor of conspecific females to the odor of females of another species. Both experienced and naive males also preferred the odor of conspecific females to that of conspecific males. Only sexually experienced males showed a significant preference for estrous over nonestrous conspecific females. Sexually experienced males also discriminated between estrous and nonestrous heterospecific females of a familiar (lemming) and unfamiliar (meadow vole, Microtus pennsylvanicus) species. In conjunction with the results of earlier studies of the development of species-specific olfactory preferences, findings suggest that 2 olfactory cues mediate a male's attraction to receptive females: a species-specific odor that is learned during early development and a sexual attractant whose saliency is established as a result of adult experience with a receptive female. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral thermoregulation in a sexually and developmentally dichromatic neotropical primate, the black-and-gold howling monkey (Alouatta caraya)

Behavioral thermoregulation in primates may provide a means for the conservation of heat during periods of low ambient temperature and/or food shortage as well as a way to dissipate heat under hot conditions. This article focuses on behavioral thermoregulation in a sexually dichromatic primate, the black-and-gold howling monkey (Alouatta caraya). Two models have been proposed to explain the evolution of sexual dichromatism in this species: thermoregulation and sexual selection. Five hypotheses associated with thermoregulatory behaviors are tested. These are as follows: (1) energy-conserving postures are used mainly under low ambient temperatures; (2) sunny resting places are selected during periods of low temperature; (3) exposure of the less-insulated ventral region to sunlight decreases with increasing temperature; (4) black-colored adult males use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight less frequently than do blonde-colored adult females; and (5) smaller individuals use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight in significantly greater frequency than do larger individuals. Over a 12-month period, behavioral data were collected on a free-ranging habituated group of 15-17 howlers of all age-sex classes. Ambient temperature was measured each hour. The results indicate that during resting, howlers showed a consistent use of heat-conserving postures, showed a preference for sunny places, and exposed their ventral region to sunlight under low ambient temperatures. A preference for shady places, heat-dissipating postures, and exposure of the back were observed under high ambient temperatures. Despite sex differences in adult color patterns and differences in size between age classes, no significant age or sex differences in thermoregulatory behaviors were detected. Failure to confirm a thermoregulation model implies that sexual selection may be responsible for sexual dichromatism in this species.     

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)     

Grafts of ovaries in males and females of Pleurodeles waltl (urodele amphibia): evidence of a long-term tolerance of allografts; application following a space biology experiment

Ovary grafts were investigated in the salamander Pleurodeles using juveniles and adults as donors and hosts. Ovaries were provided by standard or histo-compatible strains and by standard females which had been submitted to a space flight. Laparotomy of the hosts was used to control viability of grafts. Entire juvenile ovaries transplanted into castrated juvenile females or males were tolerated and developed. Ovarian parts of adult females, which contained a majority of oogonies, could also be tolerated by juvenile animals. In addition, ovarian parts supported a better recovery and differentiation than parts that mainly included mature oocytes. About 24 months after the ovary grafts, some hosts (genetical females or males and standard or spatialized females) crossed with standard males provided progenies originating from oocytes of the grafted ovaries. The protocols applied offer a new range of potentialities, adapted to various experimental purposes such as life science research in space or sex differentiation studies.     

Tactile stimulation during development attenuates amphetamine sensitization and structurally reorganizes prefrontal cortex and striatum in a sex-dependent manner.

This study investigated the effect of postnatal tactile stimulation (TS) on juvenile behavior, adult amphetamine (AMPH) sensitization, and the interaction of TS and AMPH on prefrontal cortical (PFC) thickness and striatum size. Pups received TS by stroking daily with a feather duster from birth till weaning and were tested, as juveniles, in behavioral tasks including open field locomotion, elevated maze, novel object recognition, and play fighting behavior. Development and persistence of drug-induced behavioral sensitization was tested by chronic AMPH administration and challenge, respectively. PFC thickness and striatum size were assessed from serial brain sections. The findings showed that TS rats spent less time with novel objects on first exposure but open field locomotion and elevated plus maze tasks were not affected substantially. TS reduced the frequency of play fighting and enhanced evasion in response to a playful attack, but only in males. The probability of complete rotation defense, leading to a supine posture during play, was reduced in both sexes. AMPH administration resulted in gradual increase in behavioral sensitization that persisted at least for 2 weeks. However, TS rats exhibited attenuated AMPH sensitization compared to sex-matched controls. Neuroanatomically, AMPH reduced the PFC thickness in control females but enlarged the posterior striatum in control males. TS experience blocked these effects. In summary, TS during development modulated the response to novel objects and altered social behaviors and attenuated AMPH-induced behavioral sensitization by preventing drug-induced structural alteration in the PFC and the striatum, brain regions implicated in drug abuse. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Age and sex as factors influencing spontaneous exploration and object investigation by preadult rats (Rattus norvegicus).

Examined developmental and sex differences in the exploratory and investigatory behaviors of Long-Evans rats. Littermate sextuplets were divided into sex-matched groups (at 30, 60, and 90 days of age) and were individually videotaped on 2 consecutive nights in an arena that contained stimulus objects. Multiple measures of locomotor exploration and object investigation increased significantly with age but were not influenced by sex. Older rats entered more quickly, were more active, spent more time in the arena, and spent more time investigating inanimate stimulus objects than did younger rats. Sex did not significantly affect most measures of open-field behavior; however, the data suggest that the sexes may begin to diverge by 90 days. These results suggest that preadult rats of both sexes are equipped early in development with similar strategies and repertoires for exploration and investigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex Differences in the Behavioral Response to Spatial and Object Novelty in Adult C57BL/6 Mice.

The present studies examined sex differences in object localization and recognition in C57BL/6 mice. Experiment 1 measured responses to spatial novelty (object displacement) and object novelty (object substitution). Males strongly preferred displaced and substituted objects over unchanged objects, whereas females showed a preference in only 1 measure of object novelty. Experiment 2 further examined object recognition by presenting mice with 2 identical objects, followed 24 hr or 7 days later by testing with a familiar and a novel object. After 24 hr, males preferentially explored the novel object, whereas females exhibited no such preference. Neither sex displayed a preference for the novel object after 7 days. The data suggest that male mice are superior to females at localizing and recognizing objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in facial shapes and their discrimination in Japanese monkeys (Macaca fuscata).

The authors examined the ability of Japanese monkeys (Macaca fuscata) to discriminate between sexes based on facial features. The shape and position of facial features (facial morphology) were measured to quantify the differences between sexes. The distance between the chin and nose was longer in males than females, and the outline of the face around the upper jaw and upper face differed between sexes. Using operant conditioning, 2 monkeys succeeded in discriminating sex based on facial pictures. Furthermore, they successfully generalized the discrimination to novel pictures of faces. Tests with morphed pictures of faces revealed that the monkeys used facial morphology to discriminate between males and females. Our results suggest that Japanese monkeys have sexual dimorphism in facial shape and they can use the morphological differences to discriminate conspecific sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal ethanol exposure differentially alters behavior in males and females on the elevated plus maze

Rodents prenatally exposed to ethanol demonstrate hypothalamic-pituitary-adrenal and behavioral hyperactivity to a variety of stressful situations. The present study examined both behavioral and corticosterone (CORT) responses to the elevated plus maze (+-maze), an anxiety- or fear-provoking task. Sprague-Dawley male and female offspring from fetal ethanol-exposed (E), pair-fed (PF), and ad libitum-fed control (C) groups were tested at 60 to 90 days of age. In experiment 1, behavior was measured in animals exposed to the +-maze for 5 min on two consecutive days; 2 weeks later, both behavioral and CORT responses were measured in animals confined to the open and closed arms of the maze for 20 min. In experiment 2, animals were placed in an open field (OF) for 5 min before a single 5-min exposure to the +-maze. Factor analysis of the scored behaviors from the two experiments indicated two main factors, designated "exploration" and "fear." E males and females both exhibited higher levels of exploratory behaviors when placed directly on the +-maze from their homecages without prior exposure to the OF, compared with C males and females. In addition, when confined to the closed arms of the +-maze, E males and females demonstrated higher levels of activity, compared with C males and females. After OF exposure, however, both E males and females demonstrated lower levels of exploratory behaviors than C males and females, and E females also had increased CORT levels, compared with PF and C females. Interestingly, E females, but not E males, showed an increase in fear-related behaviors on the +-maze, compared with controls, regardless of prior OF exposure. These data demonstrate that prenatal ethanol exposure may differentially affect both behavioral and hormonal responses of males and females in an aversive behavioral task and suggest that there may be a sex difference in the sensitivity of the mechanism(s) underlying these responses.     

Nucleolar size and shape is sexually dimorphic in neurons of the lateral magnocellular nucleus of the anterior neostriatum (LMAN) in birds

The lateral magnocellular nucleus of the anterior neostriatum (LMAN) in birds plays an important role in songlearning processes. Recently, it has been shown that structural changes at the cellular level in males are causally related to vocal learning. Whereas males sing, females do not. This sexual difference in behavior is also reflected in sexual differences in the neuronal structure in adult birds, with males having larger neuronal somata than do females. In the present report, the size and shape of the nucleoli were investigated to determine if sexual differences were also present at the nucleolar level. The data demonstrated a strong sexual difference in nucleolar size in both juvenile and adult birds, the cross-sectional area of the nucleoli being significantly larger in males than in females (30% and 50% larger in juvenile and adult birds, respectively). This difference between males and female finches was also reflected by the cross-sectional area of a specific type of nucleolus exhibiting a central light area. In both sexes, nucleoli exhibiting a central light area were significantly larger in juvenile and adult birds than nucleoli that lacked a central light area. The percentage of neurons exhibiting a central light area was higher in adult males than in adult females, but not in juvenile birds. The time course of development of nucleoli exhibiting a central light area in males was very similar to the development of neuronal somata size in LMAN neurons. The larger size of the nucleoli in LMAN neurons in males and the developmental changes in the incidence of nucleoli exhibiting a central light area may be indicative of a high level of ribosome production necessary for song-learning processes to occur.