Effects of neonatal cyproterone acetate administration on isolation-induced fighting behavior and mounting behavior in male and female TO strain albino mice

The effects of a single dose (1 mg) of cyproterone acetate administered on either day 1 or day 20 of life on the adult behaviors of male and female TO strain albino mice were studied. The mice were tested both in a “standard opponent”-type situation and in a similar test using a hormonally primed receptive female, after being gonadectomized and maintained with testosterone propionate as adults. Neonatal treatment with this compound had little effect on subsequent fighting behavior in either sex, but clear evidence was produced that this treatment masculinized the sexual behavioral potentialities of the females, an effect which was apparent in animals which had been injected on either day 1 or day 20 of life. Indications were obtained that females treated neonatally with cyproterone acetate were capable of differentiating between the male and female “opponents” in a manner similar to the male. The effects of this treatment on fighting behavior consequently appear to be dissimilar to the effects of neonatal castration in this species. However, the effects on mounting behavior in the females, evidenced in adulthood, seem Likely to be a consequence of the weak androgenic properties of the antiandrogen. The administration of cyproterone acetate neonatally appears to have a more dramatic effect on the adult weights of endocrine organs in females than in mates.     

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

Two experiments were conducted to examine 70-kHz ultrasonic courtship vocalizations by adult male mice (Mus musculus) to novel odors following exposure to these odors in infancy and/or adulthood. The research was performed in hopes of better understanding the experiences giving rise to vocalizations to naturally occurring chemosignals. Experiment 1 demonstrated that adult males normally do not vocalize to the urine of female rats but would come to do so 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. Experiment 2 was designed to examine vocalizations to the urine of female mice whose urinary odor was altered by the ingestion of fenugreek, a spice. Although the magnitude of the effect was smaller in this experiment, greater amounts of vocalization again were seen by males that as adults encountered females that had ingested fenugreek. Males with such experience also showed a small but significant elevation in vocalizations to the fenugreek odor itself. 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. Thus vocalizations to two different novel odors occurred only after an adult male had encountered an adult female odorized with the novel odor. On the other hand, none of the novel odor experiences eliminated vocalizations to the naturally occurring chemosignal in female mouse urine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sensory cues that elicit ultrasonic vocalizations in female rats (Rattus norvegicus)

Female rats emit ultrasonic vocalizations during copulation. Female vocalizations are associated with darting and other proceptive behavior. In addition, females frequently call while approaching the male. A series of experiments was undertaken to determine whether female rats emit ultrasonic vocalizations in response to other rats or to their odors. Females were exposed either to bedding soiled by males or females or to devocalized conspecifics separated from the subject by a barrier. Females vocalized more to male cues than to female cues, regardless of whether the odor cues were from soiled bedding or from a devocalized conspecific. In addition, subjects vocalized more when presented with a devocalized female rather than a neutral stimulus. Furthermore, devocalized adult males, separated by a barrier, were more effective than either devocalized castrated or juvenile males in eliciting vocalizations; in turn, castrates and juveniles were more effective than neutral stimuli. Female calling was likely induced by odors from the male. In one experiment, the female subject was positioned in such a way that she could neither see or touch the stimulus male. Presentation of tape-recorded male vocalizations did not affect calling by the female. Vocalizations emitted by females in response to male odors may attract males or may facilitate subsequent copulatory behavior by the male.     

Ultrasonic vocalizing by adult female mice (Mus musculus)

Though an extensive body of literature exists concerning the emission of 70-kHz ultrasonic vocalizations by adult male mice (Mus musculus), almost nothing is known about the ultrasonic vocalizing of adult females. A series of five experiments was conducted to examine adult female mouse ultrasound emission. Results indicated female ultrasonic vocalizing to be typically displayed among female mouse dyads and comparable to the ultrasonic vocalizing levels obtained among male-female pairs. Genotypically based variations in the production of ultrasounds by females were also noted. Like male mice, socially naive females readily ultrasonically vocalized to anesthetized female conspecifics and rarely vocalized to anesthetized males. Unlike males, socially experienced females emitted few ultrasounds to either female urine or female-soiled cage shavings. Although social experience served to increase the ultrasound emission of male mice to female sex cues, the production of ultrasounds by females to these cues was decreased by social experience. Implications with regard to the existence of a behavioral/functional sexual dimorphism in adult mouse ultrasonic vocalizing are discussed.     

The expression of the genes of aggressiveness in mice: The effect of androgen on aggression and sexual behavior in females

Female mice of strains selectively bred for aggressiveness or nonaggressiveness were injected with testosterone propionate (TF′) at the age of 2 days and as adults, or they were injected as adults only. Aggressive and sexual behavior was then tested with female, receptive female, and male partners before, during, and after the latter TP treatment. The females that had received both TP treatments displayed as much or as little aggression as males of the same strain, leading to the conclusion that aggressiveness genes are not linked with the male sex chromosome, even though they depend on it for their expression. The sexual behavior of the females of both strains that had received both TP treatments was altered to the male type. In the females of the aggressive strain even adult treatment alone was sufficient for this change. Aggressiveness and male sexual behavior would seem to be determined separately, although aggressiveness facilitates the display of male sexual behavior.     

Short-term early exposure to pups alters infanticide in adulthood in male but not in female wild house mice (Mus domesticus)

Male and female wild house mice (Mus domesticus) were allowed to remain in the cage of their parents until 30-35 days of age. When a second litter was delivered, the first litter was exposed to the younger pups for 2-10 days. In adulthood the male and female mice that had been exposed to pups as juveniles and an additional group that had cohabitated with their parents for the same length of time but were not exposed to pups were tested for infanticidal behavior. The frequency of infanticide by the adult female mice was not significantly different (55% vs. 70%, respectively). In contrast, the adult males that were exposed to pups as juveniles were significantly less likely to kill young in adulthood when compared with males that were not similarly exposed (35% vs. 80%, respectively). These data further demonstrate the strong influence of experience on the expression of infanticide by male mice and its relative unimportance to the expression of female infanticide.     

围生期双酚A暴露对不同性别子代小鼠行为的影响

探讨围生期母体双酚A(bisphenol A, BPA)暴露对幼年期(生后21~30天, postnatal day 21~30, PND 21~30)和青年期(生后56~63天, PND 56~63)不同性别子代小鼠行为的影响。母鼠从妊娠第7天至断乳前(产后21天)进行BPA(0.05、0.5、5、50 mg/kg/day)灌胃染毒, 同时设对照组。每个剂量组分别在PND 21和PND 56开始测试雌雄子代小鼠各项行为。以旷场行为检测小鼠的自发活动及探究行为, 以高架十字迷宫检测小鼠的焦虑行为, 以水迷宫检测小鼠的空间学习记忆能力, 以跳台检测小鼠的被动回避记忆行为。结果表明, BPA使PND 21雌雄子鼠和PND 56雄性子鼠自发活动减少(p<0.05或p<0.01), 理毛和站立行为发生性别分化(p<0.05或p<0.01); PND 21子鼠的3分钟跑动格数有明显的剂量效应关系, 其中5~50 mg/kg/day组特别显著。BPA显著增加PND 21雌雄子鼠和PND56雌性子鼠在高架十字迷宫中进入开放臂次数和停留时间(p<0.05或p<0.01)并减少封闭臂的进入时间, 但没有明显的剂量效应关系; BPA减少PND 56雄性子鼠开放臂的进入并增加其封闭臂的进入, 干扰了幼年期和青年期小鼠焦虑行为的性别分化。BPA剂量依赖性地延长PND 21和PND 56雄性子鼠在水迷宫搜索平台的平均距离, 其中5~50 mg/kg/day剂量组具有差异显著性(p<0.05或p<0.01), 但对雌性子鼠空间学习记忆行为没有影响。此外, 5~50 mg/kg/day BPA增加PND 21雄性子鼠在跳台实验中的错误次数并缩短其跳下平台潜伏期, PND 56雌雄子鼠的被动回避记忆仅被50 mg/kg/day BPA减弱。以上结果提示, 围生期BPA暴露可影响子代小鼠幼年期和青年期的多种行为及行为的性别差异, 不同行为对BPA的敏感程度不同, 其中以自发活动和探究行为最敏感。     

Responsiveness to estrous chemostimuli in male rats (Rattus norvegicus) of different ages

Previous findings indicate that Norway rats (Rattus norvegicus) respond differentially to estrous chemostimuli in early infancy and that adult male sexual responsiveness to such chemostimuli depends on infantile experience with suckling odors (Fillion & Blass, in press). The development of behavioral responsiveness to estrous chemostimuli in male rats from late infancy to adulthood was examined in this study. Preweanling, adolescent, and adult males were observed for 20 min in the presence of an anesthetized estrous or an anesthetized diestrous female. This was, for adolescent and adult subjects, the first heterosexual encounter since weaning. Rats in each age-group responded differentially according to female state, but in distinct, age-related ways. Preweanling spent more time investigating the female's body if she was estrous. Adults expressed the same affinity but by more focused investigation directed perivaginally. Adolescents showed no female-directed bias but groomed themselves more if the female was estrous. These data identify developmental continuities and discontinuities in male rat behavior toward sexually receptive females.     

Long-term continuous, but not daily, environmental enrichment reduces spatial memory decline in aged male mice

Although environmental enrichment improves spatial memory and alters synaptic plasticity in aged rodents, it is unclear whether all types of enrichment treatments yield similar benefits. The present study examined the effects in aged male mice of three types of enrichment on spatial memory in Morris water maze and radial arm maze tasks, and on levels of the presynaptic protein synaptophysin in several brain regions. Non-enriched young and aged males were compared with males exposed to one of the following treatments for 10 weeks: 5 min of daily handling, 3 h of daily basic enrichment, or 24 h of continuous complex enrichment. Young controls outperformed aged controls in both tasks. Neither daily handling nor daily enrichment affected spatial memory or synaptophysin levels. In contrast, continuous enrichment significantly reduced age-related spatial memory decline in both tasks, such that this group was statistically indistinguishable from young controls in most measures of performance. Continuously enriched mice were also significantly better than other aged mice in several spatial memory measures. Despite these improvements, synaptophysin levels in the continuous enrichment group were significantly lower than those of young and aged controls in the frontoparietal cortex, hippocampus, and striatum, suggesting a negative relationship between synaptophysin levels and spatial memory in aged males. These data demonstrate that different types of enrichment in aged male mice have disparate effects on spatial memory, and that the relationship between enrichment-induced changes in synaptophysin levels and spatial memory in aged males differs from that we have previously reported in aged female mice.     

Categorization and normalization of vowels by 3-year-old children

A two-alternative, forced-choice procedure was used in two experiments to test 3-year-old children’s categorization of natural vowel tokens produced by several talkers. An appropriate pointing response (right or left) was visually reinforced with one of two television displays. In Experiment 1, the stimuli were isolated tokens of /a/ and /i/ produced by a male adult, a female adult, a male child, and a female child. In Experiment 2, the stimuli were isolated tokens of /æ/ and /∧/ produced by the same talkers. In both experiments, 3-year-olds spontaneously generalized their pointing responses from the male adult vowel tokens to the corresponding vowels produced by the other talkers. Children reinforced for an arbitrary grouping of the two vowel categories persisted in categorizing on the basis of vowel quality. Results from both experiments demonstrate the presence of perceptual constancy for vowel tokens across talkers. In particular, the results from Experiment 2 provide evidence for normalization of isolated, quasi-steady-state vowel tokens because the formant values for tokens of /∧/ produced by the woman and the two children were closer to the formant frequencies of the male adult’s /æ/ than to the male adult’s /∧/.     

Perinatal exposure to diethylstilbestrol improves olfactory discrimination learning in male and female Swiss-Webster mice

During late prenatal and early postnatal brain development, estrogen induces structural sex differences that correspond to behavioral differences in certain domains such as learning and memory. The typically superior performance of males is attributed to the action of elevated concentrations of estrogen, derived inside neurons from the aromatization of testosterone. In contrast, female performance appears dependent on minimal estrogenic activity. Rat models of the relationship between hormones and cognitive behavior predominate the field, but the advent of genetically modified mice as research tools necessitates development of analogous mouse models. This study examined how early postnatal exposure to the synthetic estrogen diethylstilbestrol (DES) affected the ability of male and female Swiss-Webster mice to learn a two-choice olfactory discrimination and three repeated reversals. Mice treated with subcutaneous injections of DES from postnatal days 1-10 learned reversals more readily than oil-treated controls, a difference that became evident after repeated testing. DES-exposed males and females learned reversals at a comparable rate, suggesting that early postnatal estrogen exposure does not influence this mode of learning through a sexually differentiated mechanism in mice. An analysis of response patterns during qualitatively different phases of reversal learning revealed that DES-induced improvements probably were not due to greater inhibitory control. Instead, DES appeared to enhance associative ability. Early postnatal estrogen exposure may have the potential to preserve certain cognitive skills in adulthood.     

Female Prairie Deer Mice Prefer Conspecific Flesh Over Contraspecific Flesh

Hungry adult female deer mice were presented with freshly asphyxiated conspecifics and house mice. The deer mice showed a reliable preference for the conspecific flesh during the first 2 hr of testing, but this preference was attenuated during the following 20 hr of testing. Previous research has shown that male deer mice prefer contraspecific flesh. The preference of female deer mice for conspecific flesh is attributed to their tendency to be more aggressive toward living conspecifics than are male deer mice and their tendency to avoid living contraspecifics more than do male deer mice.     

Female prairie deer mice prefer conspecific flesh over contraspecific flesh

Hungry adult female deer mice were presented with freshly asphyxiated conspecifics and house mice. The deer mice showed a reliable preference for the conspecific flesh during the first 2 hr of testing, but this preference was attenuated during the following 20 hr of testing. Previous research has shown that male deer mice prefer contraspecific flesh. The preference of female deer mice for conspecific flesh is attributed to their tendency to be more aggressive toward living conspecifics than are male deer mice and their tendency to avoid living contraspecifics more than do male deer mice.     

5-羟色胺基因缺陷增强急性应激后高唤醒状态

剧烈的应激刺激会引起持续的高唤醒状态, 是多种应激障碍的核心症状, 并推进其他症状的发生发展。本研究关注5-羟色胺在应激诱发高唤醒的发生、发展中的作用, 通过测量听觉惊吓反射水平反映高唤醒状态, 考察色氨酸羟化酶-2基因缺陷小鼠在天敌或电击应激前后高唤醒的变化。研究发现, 雄性基因缺陷小鼠在应激后出现持续一周以上的高唤醒表现, 而野生型小鼠高唤醒状态很快恢复。结果提示, 基因缺陷引起的5-羟色胺降低可能是强应激诱发的持续高唤醒的易感因素。     

Food deprivation: Effects on the predatory behavior of southern grasshopper mice (Onychomys torridus)

The southern grasshopper mouse (Onychomys torridus) is a predatory and aggressive rodent native to the semi-arid scrub deserts of the southwestern United States and northern Mexico. Its natural diet consists primarily of arthropods and small vertebrates. In this study, we have evaluated the effects of food deprivation on the predatory behavior of adult male and female grasshopper mice to crickets (Acheta domesticus) and laboratory mice (Mus musculus). Subjects that were food-deprived for 48 hours spent more time eating dead but not living crickets than did controls that were provided free access to laboratory chow. There were no sex differences in the predatory behavior of grasshopper mice to living or dead crickets. Food deprivation also influenced the predatory behavior of grasshopper mice toward laboratory mice. With laboratory chow available ad lib, 6 of 43 (14%) male and 22 of 45 (49%) female grasshopper mice killed and ate laboratory mice within 48 hours of pairing. When deprived of food for 48 hours, 16 of 36 (44%) males and 15 of 19 (79%) females that did not kill in the previous experiment killed and ate laboratory mice. We concluded that food deprivation and type of prey are two variables which influence the frequency and intensity of predatory behaviors of grasshopper mice.     

Memory impairments and hippocampal modifications in adult rats with neonatal isolation stress experience

Early life events have profound consequences. Our research demonstrates that the early life stress of neonatal isolation (1-h individual isolation on postnatal days 2-9) in rats has immediate and enduring neural and behavioral effects. Recently, we showed neonatal isolation impaired hippocampal-dependent context conditioned fear in adult rats. We now expand upon this finding to test whether neonatal isolation impairs performance in inhibitory avoidance and in the non-aversive, hippocampal-dependent object recognition task. In addition to assessments of hippocampal-dependent memory, we examined if neonatal isolation results in cellular alterations in the adult hippocampus. This was measured with antibodies that selectively label calpain-mediated spectrin breakdown product (BDP), a marker of cytoskeletal modification that can have neuronal consequences. Neonatally isolated male and female rats showed impaired performance in both memory tasks as well as elevated BDP levels in hippocampal immunoblot samples. In tissue sections stained for BDP, the cytoskeletal fragmentation was localized to pyramidal neurons and their proximal dendrites. Interestingly, the hippocampal samples also exhibited reduced staining for the postsynaptic marker, GluR1. Neonatal isolation may render those neurons involved in memory encoding to be vulnerable to calpain deregulation and synaptic compromise as shown previously with brain injury. Together with our prior research showing enhanced striatal-dependent learning and neurochemical responsivity, these results indicate that the early experience of neonatal isolation causes enduring yet opposing region-specific neural and behavioral alterations.     

Socially induced delayed reproduction in female Mongolian gerbils (Meriones unguiculatus): is there anything special about dominant females?

In 4 experiments, the authors explored effects of interaction with both sexually active adult female and unfamiliar adult male Mongolian gerbils (Meriones unguiculatus) on young female gerbils' ages at first parturition. Presence of a natural mother retarded development of her daughters. However, presence of a natural mother had no greater effect on her daughters' development than did presence of any other familiar animal, either male or female. Further, exposing young female gerbils to an unfamiliar male accelerated their development even when their reproductively active mothers were present. The data indicate that maintaining young female gerbils in stable family groups results in both inhibition of sexual maturation (caused by exposure to familiar individuals) and failure to activate sexual development (caused by lack of exposure to unfamiliar males).     

Selective approach to a male and subsequent receptivity to mounting comprise mate‐choice behavior of female mice1

Abstract: To ensure the effectiveness of the mate‐choice behavior of female house mice (Mus domesticus), we observed them in two different situations that involved restriction of the area of movement of the male mice. In Experiment 1, we observed 12 trios consisting of two male mice and an estrous female placed in a chamber in which none of the animals was restricted during the 6‐h test. It was found that the female was more receptive to the male that had ejaculated with it first. Additionally, when the female initiated the mating event by approaching the male, the lordosis quotient was higher than that when the male initiated the mating event. In Experiment 2, a female was able to visit two males that were prevented from getting out of small boxes. As a result of the 3‐h observation of 10 cases, it was found that the females were more receptive to the dominant male. The intromission ratio of the dominant male was also higher than that of the subordinate male. The behavioral roles of female mice in mating interactions and their adaptive validity are discussed.     

Poly I:C母体免疫刺激诱导的子代精神分裂症神经发育动物模型研究

精神分裂症是一组病因未明的重性精神障碍,其病理生理学机制极其复杂,建立能够确切模拟精神分裂症的动物模型对于其发病机制的研究及抗精神分裂症药物的研发具有十分重要的意义。本文意在介绍产前母体免疫刺激（聚肌胞苷酸聚肌苷酸-聚胞苷酸,poly-I:C）诱导子代出现精神分裂症样的神经发育动物模型,以及该模型对精神分裂症的病因研究、生物学机制及其治疗和药物研发的重要意义。     

Genetics of neuronal migration in the cerebral cortex

The development of the cerebral cortex requires large-scale movement of neurons from areas of proliferation to areas of differentiation and adult function in the cortex proper, and the patterns of this neuronal migration are surprisingly complex. The migration of neurons is affected by several naturally occurring genetic defects in humans and mice; identification of the genes responsible for some of these conditions has recently yielded new insights into the mechanisms that regulate migration. Other key genes have been identified via the creation of induced mutations that can also cause dramatic disorders of neuronal migration. However, our understanding of the physiological and biochemical links between these genes is still relatively spotty. A number of molecules have also been studied in mice (Reelin, mDab1, and the VLDL and ApoE2 receptors) that appear to represent part of a coherent signaling pathway that regulates migration, because multiple genes cause an indistinguishable phenotype when mutated. On the other hand, two human genes that cause lissencephaly (LIS1, DCX) encode proteins that have recently been implicated as regulators or microtubule dynamics. This article reviews some of the mutant phenotypes in light of the mechanisms of neuronal migration. MRDD Research Reviews 6:34-40, 2000.