The temperature relations of vocalization in infant Golden hamsters and Wistar rats

Environmental temperature changes are capable of evoking ultrasonic responses from the young of Wistar rats and Golden hamsters. The changes with age in the intensity of these sounds and the rate of calling are found to be related to the pattern of development of homiothermy in the two species. In the Golden hamster, the same temperature changes also evoke audible calls which show a different pattern of variation with age. These findings are discussed in comparison with those previously reported for albino mice.     

The effect of environmental temperature on the production of ultrasounds by isolated non-handled albino mouse pups

Albino mouse pups develop homoiothermy during the first 19 days of their life and show three distinct stages during this period. From day 1 to day 6 they are almost completely poikilothermic at low ambient temperatures; from day 7 to day 14 or 15 is a transitional period during which they develop homoiothermy at medium temperatures (e.g. 22°C); from day 15 or 16 to day 19 or 20 is the final stage when homoiothermy at very low ambient temperatures is developed. These changes are very closely correlated with changes in the ultrasounds produced by isolated pups within the 19 day period. Thus their acoustic response to cold is weak from day 1 to day 5 or 6 and very strong from day 6 or 7 to day 12 or 13, on exposure even to medium temperatures. From day 14 onwards the pups progressively stop producing ultrasounds depending on the ambient temperatures, and there is complete cessation of calling after day 19 or 20 even on exposure to temperatures as low as 2°C. In general, decreasing the ambient temperatures increases the rate and intensity of ultrasounds produced but very low ambient temperatures have an inhibiting effect and at 2–3°C breathing and calling cease completely after a time which varies with age of the pups.     

Hormonal Responses of Male Gerbils to Stimuli from Their Mate and Pups

Following copulation and cohabitation with a pregnant female, male gerbils show high levels of parental behavior toward their pups. The initiation of male parental behavior may be the result of neuroendocrine changes induced by cohabiting with the pregnant female or by pup stimuli. Experiment 1 examines the changes in androgen and prolactin levels in male gerbils cohabiting with females over the reproductive cycle. Gerbils were mated and blood samples taken from males for hormone analysis 1, 10, and 20 days after pairing and 3, 10, and 20 days after pups were born. A group of unmated male gerbils served as controls. Plasma prolactin levels of males were elevated throughout the female's pregnancy and lactation periods, but were only statistically significantly higher than those of unmated males 20 days after pups were born. Androgen levels rose during pregnancy and dropped significantly after the birth of the pups. These hormonal changes are similar to those found in males of monogamous birds and differ from those found in males of polygynous rodents such as the rat. Experiment 2 examined the hormonal responses of male and female gerbils to pup replacement after 4 hr of parent–pup separation. Female gerbils showed a significant elevation of prolactin levels 1 hr after pup replacement, but males did not. Males with pups returned showed no difference in androgen levels from males who did not have pups returned. Thus, male gerbils show neuroendocrine changes following long-term cohabitation with their mate and pups, but do not show acute hormone responses to pup removal and replacement. These results indicate that parental males have neuroendocrine changes associated with parental behavior and these differ from the neuroendocrine changes underlying female parental behavior.     

Thermoregulation and diurnal rhythms in 1-week-old rat pups

This paper reviews the ontogeny of thermoregulation and diurnal rhythmicity in rats. Additionally, original data are presented that indicate the emergence of an endogenous circadian core temperature rhythm during the first postnatal week. Despite neurological immaturity, newborn rats display autonomic and behavioral thermoregulatory responses within 24 h of birth. Their "biological clock" is already running before birth. The thermal environment of pups changes cyclically owing to diurnal variations in maternal behavior, but the core temperatures of 1-week-old pups huddling in the absence of the dam also show marked diurnal fluctuations. Five- to 8-day-old lean Zucker rat pups artificially reared in the absence of 24-h cycles of ambient temperature and food intake show diurnal changes in core temperature similar to those in huddling mother-reared pups. Diurnal core temperature changes, evident only when regulatory effectors are not overwhelmed, are one of the first self-maintained diurnal rhythms to appear. Because thermoregulation and circadian rhythmicity both appear before maturation of the neural networks believed to be critical for their control in adult animals, studying the immature rat might increase our understanding of the control of these processes in the more complex mature central nervous system.     

Strain Differences in the Ultrasonic Behavior of Rats (Rattus Norvegicus)

Wistar rat pups are generally more "vocal" than Lister pups;the ultrasonic calls that they produce are usually louder andemitted at a greater rate than those of Lister pups of the sameage and studied under similar conditions of isolation or handling.These differences in ultrasonic behavior are apparently notrelated to differences in the development of homiothermy whichfollows a similar course in both strains. The calls of infantsof the two strains do not show any marked differences in durationor frequency pattern that are consistent over age or treatmentcondition, but the Wistar pups appear to show greater changeswith age than the Lister pups in certain parameters of the calls,while the latter strain show greater changes with treatmentcondition. Similar strain differences in the rate and intensity of callingwere seen during aggressive encounters between adult males,but these cannot be related to differences in aggressive behavior.The strains differ in the duration of both the long "22 kHz"calls (Lister greater than Wistar) and the shorter "50 kHz"calls (Wistar greater than Lister), as well as in the minimumfrequency of these shorter calls (lower in Wistar than in Listerrats).     

Transient changes of cortical interhemispheric responses after repeated caffeine administration in immature rats

Repeated postnatal caffeine treatment of rat pups led to transient developmental changes in cortical epileptic afterdischarges. To know if physiological cortical functions are also affected transcallosal evoked potentials were studied. Rat pups of the Wistar strain were injected daily with caffeine (10 or 20 mg/kg s.c.) from postnatal day (P) 7 to P11, control siblings received saline. Cortical interhemispheric responses were tested at P12, 18, 25 and in young adult rats. Amplitude of initial monosynaptic components was evaluated in averaged responses. Single pulses as well as paired and frequency (five pulses) stimulations were used. Developmental rules - highest amplitude of responses in 25-day-old rats, potentiation with paired and frequency stimulation present since P18 - were confirmed. Caffeine-treated rats exhibited transient changes: single responses were augmented in P25 if high stimulation intensity was used, paired-pulse and frequency responses were higher in experimental than in control animals at P12, the opposite change was observed in 18- and more markedly in 25-day-old rats. No significant changes were found in adult animals, monosynaptic transcallosal responses represent a simple and robust system. The developmental profile of described changes did not exactly correspond to changes in epileptic afterdischarges supporting the possibility that afterdischarges did not arise from early monosynaptic components of responses. In spite of transient nature of changes they can reflect delayed or more probably modified brain development.     

Responses of Odonata chromatophores to environmental stimuli

Responses to change in temperature and light intensity were studied in three species of Australian Odonata using time-lapse photography. In each species, responses to temperature are dependent on both the instantaneous temperature and the direction of temperature change. At temperatures below those which produce unstable colour phases, the change to dark phase takes about 9 hr and is constant in rate. The reverse change is directly temperature dependent and can be much more rapid. Responses to change in light intensity are attributable to the heating effect of light rather than to true light sensitivity. All colour changes show wide individual variation in both rate and amount. They are slightly affected by temperature acclimation but are unaffected by prevailing weather, time of year, geographic location, or age.     

Response of Wolves to Experimental Disturbance at Homesites

ABSTRACT Events during the denning period (parturition to first autumn) often determine the reproductive success of wolves (Canis lupus). Consequently, there is concern about the potential adverse effects of human-caused disturbance at wolf den and rendezvous sites (homesites), but relatively little information on this subject is available. We conducted standardized experimental disturbance treatments at 12 unique wolf homesites in the Northwest Territories, Canada, during summers 2002 and 2003. The treatment consisted of an intruder approaching a homesite once per day for 3 consecutive days and recording behavioral responses, response distance, and response intensity of wolves. We counted pups and estimated their ages prior to the initial treatment at each site. Adult wolves moved pups at 3 of 6 treated homesites in each year. The amount and type of known human activity within a pack's home range did not influence whether adults moved pups in response to the treatment. The response intensity of wolves to the treatment was inversely related to the amount of human activity near a homesite. There was no relationship between the distance at which wolves responded to the intruder and the amount or type of human activity. There was a positive relationship between increasing age of pups and their relocation in response to the treatment. Reproductive success was not influenced by the treatment or by the amount and type of human activity. Treated sites were used by wolves the following year in the same proportion as untreated sites. It appears that pups are most vulnerable early in the year when less mobile; therefore, managers should consider age of pups before human activity at or near wolf homesites occurs.     

Repeated maternal separation in the neonatal rat: cellular mechanisms contributing to brain growth sparing.

Separation of neonates from their dam has been shown to evoke acutely a variety of biochemical responses, typified by depression of ornithine decarboxylase (ODC) activity. In the current study where rat pups were removed from their nursing dams for 6 h, ODC activities in the liver, heart, kidney and lung were markedly suppressed, but the enzyme in the brain was not altered during the early postnatal ages. These data suggest that the brain was protected from maternal separation insults, a homeostatic response mediated in part, by an increase of circulating corticosterone and glycogen mobilization from peripheral tissues, particularly the liver. In addition, we examined whether these responses were extended to pups who were subject to repeated episodes of maternal deprivation, and whether this stress paradigm might be associated with corresponding changes of cellular growth and maturation. Pups were removed from their dams for 6 h daily beginning at 4 days of age until weaning at 21 days. Plasma corticosterone levels of the deprived pups were elevated significantly at the end of each stress episode but returned to basal (control) levels subsequently. The repeating stress paradigm did not influence the magnitude of this hormonal response at the ensuing ages. Consistent with findings observed in the single episodes of stress, ODC activities in the peripheral tissues were significantly depressed in pups subject to repeated maternal deprivation, but the enzyme appeared to recover to control levels 18 h after each insult. In contrast, brain ODC activity did not exhibit any change throughout the period examined. Moreover, while ontogenetic gains of DNA and protein in the peripheral tissues of the deprived rats lagged slightly but consistently behind those of controls, these macromolecules in the brain were not affected appreciably. These results thus suggest that brain growth was, by and large, spared from insults associated with repeated maternal separation; but this stressful paradigm did produce marked, though reversible biochemical and physiological responses in the peripheral tissues of neonates, which cumulatively led to a lag of cellular development.     

Characterizing the functional significance of the neonatal rat vibrissae prior to the onset of whisking

The present series of experiments assessed how information from the whiskers controls and modulates infant rat behavior during early learning and attachment. Passive vibrissal stimulation can elicit behavioral activity in pups throughout the first two postnatal weeks, although orienting to the source of stimulation is evident only after ontogenetic emergence of whisking. In addition, while pups were capable of demonstrating learning in a classical conditioning paradigm pairing vibrissa stimulation with electric shock, no corresponding changes were detected in the anatomy of the barrel cortex as determined by cytochrome oxidase (CO) staining. Finally, the role of whiskers in a more naturalistic setting was determined in postnatal day (PN)3-5 and PN11-12 pups. Our results showed that both nipple attachment and huddling were disrupted in whisker-clipped PN3-5 pups but only marginally altered in PN11-12 pups. Together, these results suggest that the neonatal whisker system is behaviorally functional and relevant for normal mother-infant interactions, though it lacks the sophistication of a mature whisker system that evokes very specific and directed responses.     

Characterizing the functional significance of the neonatal rat vibrissae prior to the onset of whisking

The present series of experiments assessed how information from the whiskers controls and modulates infant rat behavior during early learning and attachment. Passive vibrissal stimulation can elicit behavioral activity in pups throughout the first two postnatal weeks, although orienting to the source of stimulation is evident only after ontogenetic emergence of whisking. In addition, while pups were capable of demonstrating learning in a classical conditioning paradigm pairing vibrissa stimulation with electric shock, no corresponding changes were detected in the anatomy of the barrel cortex as determined by cytochrome oxidase (CO) staining. Finally, the role of whiskers in a more naturalistic setting was determined in postnatal day (PN)3-5 and PN11-12 pups. Our results showed that both nipple attachment and huddling were disrupted in whisker-clipped PN3-5 pups but only marginally altered in PN1I 1-12 pups. Together, these results suggest that the neonatal whisker system is behaviorally functional and relevant for normal mother-infant interactions, though it lacks the sophistication of a mature whisker system that evokes very specific and directed responses.     

Strategic adjustment of begging effort by banded mongoose pups

Variation in the intensity of conspicuous displays raises three basic questions: (i) the relationship between internal state and display intensity, (ii) the relationship between display intensity and receiver response, and (iii) the effect of variation in receiver responsiveness on signaller behaviour. Here, I investigate the interaction between pups and helpers in the communally breeding banded mongoose (Mungos mungo), where each pup forms an exclusive relationship with a single adult helper (termed its 'escort'). By experimentally manipulating pup need, I demonstrate that changes in begging rate correspond to changes in short-term need. The data then suggest that escorts in good condition may be more responsive to increased begging and that pups associating with them increase their begging more than do pups paired with escorts in poor condition. Escorts also appear more responsive to increased begging by female pups, and female pups increase their begging more than do male pups. These results suggest that banded mongoose pups may strategically adjust their investment in begging in relation to variation in the expected pay-off. I argue that such adjustment is likely to be a general phenomenon: wherever there is variation in responsiveness to signals, signallers will be selected to identify different categories of receiver and adjust their signals in order to maximize the pay-offs. Therefore, differences in signal intensity may be as much a product of context as an indication of variation in individual phenotypic or genotypic state.     

大绒鼠幼仔的生长发育和产热特征

为阐明大绒鼠幼仔的生长发育和代谢产热特征,本实验测定了1-49 日龄大绒鼠幼仔的体重、体温、静止代谢率(RMR)和非颤抖性产热(NST)。依据逻辑斯蒂曲线的拐点(24 d),大绒鼠的体重生长可划分为加速生长相和减速生长相,幼仔的体温在19 日龄前逐渐升高,22 日龄时接近成体水平;RMR 和NST分别在28日龄、19日龄前随日龄逐渐增加,RMR 在28日龄时接近成体水平,BAT 产热活性在7 日龄内被激活。结果表明,大绒鼠胎后发育及产热能力符合晚成性动物的一般特征,即具有短的妊娠期,较少的胎仔数,较长的哺乳期,这些特征对适应横断山特殊多变的环境条件具有重要意义。     

The effect of ambient temperature on body temperature and on ultrasonic behaviour in litters of albino laboratory mice deprived of their mothers

Litters of mouse pups of various ages when deprived of their mother and kept for one hour at ambient temperatures of 3°C, 12°C and 22°C lose heat less rapidly than pups isolated individually at similar temperatures. The litters are able to maintain constant body temperatures of 35–37°C by day 8 at 22°C, by day 19 at 12°C and by day 21 at 3°C. Very little ultrasound is detected from litters of any age up to 21 days at 22°C while at 12°C ultrasound is mainly detected from pups of 4 and 6 days; very few calls are produced by older pups at this temperature. Considerably more calls are emitted at 3°C than at either of the two higher temperatures. At 3°C the total number of calls emitted during the hour-long exposure period varied markedly with age. There were two peaks of calling, one on day 6 and the other on day 16. The temporal pattern of calling throughout the hour-long exposure period at 3°C was similar in pups of 4 and 6 days and in pups of 8, 10, 12, 14 and 16 days, but differed between these two groups. In the younger group of pups the rate of calling rose to a peak and then decreased to zero as the pups became comatose; in the older pups the rate of calling was low initially then either rose throughout the rest of the hour or rose to a high level that was maintained. It is suggested that the various patterns of ultrasonic calling can be associated with the physiological development of mouse litters.     

Influence of core temperature on autoresuscitation during repeated exposure to hypoxia in normal rat pups.

Failure to autoresuscitate by hypoxic gasping during prolonged sleep apnea has been suggested to play a role in sudden infant death. Furthermore, thermal stress brought about by a contribution of infection, overwrapping, or excessive environmental heating has been shown to be associated with an increased risk of sudden infant death, particularly in prone sleeping infants. The present experiments were carried out on newborn rat pups to investigate the influence of "forced" changes in core temperature on their time to last gasp during a single hypoxic exposure and on their ability to autoresuscitate during repeated exposure to hypoxia. On day 5 or 6 postpartum the pups were placed in a temperature-controlled chamber regulated to 33, 35, 37, 39, or 41 degrees C and exposed to a single period of hypoxia (97% N(2)-3% CO(2)) and their time to last gasp was determined, or they were exposed repeatedly to hypoxia and their ability to autoresuscitate from primary apnea was determined. Increases in core temperature brought about by changes in ambient temperature from 33 to 41 degrees C decreased the time to last gasp after a single hypoxic exposure and decreased the number of successful autoresuscitations after repeated hypoxic exposures. Thus our data support the hypothesis that forced changes in core temperature brought about by changes in ambient temperature influence protective responses in newborns that may prevent death during hypoxia, as may occur during single or repeated episodes of prolonged sleep apnea.     

In vivo development of brain phosphocreatine in normal and creatine-treated rabbit pups

To study the effects of creatine (Cr) on brain energy metabolism and on hypoxia-induced seizures, 5- to 30-day-old rabbit pups were given subcutaneous Cr (3 g/kg) for 3 days before exposure to 4% O2 for 8 min. In saline-treated controls, hypoxic seizures were most frequent at 15 days (80% of pups) and 20 days (60%) of age. Seizures were prevented at 15 days and reduced 60% at 20 days in Cr-treated pups. In surface coil-localized brain 31P nuclear magnetic resonance spectra, with signal from both cerebral gray (GM) and white (WM) matter, the phosphocreatine (PCr)/nucleoside triphosphate (NTP) ratio doubled between 5 and 30 days of age in controls. In all Cr-injected pups, brain PCr/NTP increased to values seen in 30-day-old controls. When spectra were acquired in predominantly GM and WM slices in vivo, the PCr/NTP ratio was very low in GM at 5 days but reached adult levels by 15 days in controls. In WM, the ratio increased steadily from 5 to 30 days of age. In Cr-injected pups, PCr/NTP increased to mature levels in WM and in GM at all ages. In conclusion, hypoxic seizures occur midway in the time course of brain PCr/NTP increase in rabbit pups as previously described in rat pups. In both altricial pups, systemic Cr increases brain PCr/NTP ratio and prevents hypoxic seizures. These results suggest that mature levels of PCr and/or Cr in brain limit EEG activation either directly or indirectly by preventing hypoxic metabolic changes.     

Neonatal sex steroids affect ventilatory responses to aspartic acid and NMDA receptor subunit 1 in rats.

We hypothesized that administration of estradiol benzoate to males and testosterone propionate to female neonatal rat pups alters sex-specific ventilatory responses to aspartic acid with correspondent changes in N-methyl-D-aspartate receptor subunit 1 (NR1) expression determined by Western blot in specific brain regions. One-day-old rat pups received estradiol benzoate, testosterone propionate, or vehicle and were studied at weanling and adulthood. Different groups had distinct patterns of changes in tidal volume and frequency of breathing after aspartic acid administration. NR1 expression in hypothalamus was altered by age, sex, and treatment. Medullary and pontine NR1 expression correlated with baseline ventilation and magnitude of the ventilatory response to aspartic acid in some groups. Thus 1) tidal volume and breathing frequency patterns in response to aspartic acid are gender, age, and treatment dependent; 2) sex, age, and exogenous steroid hormones affect NR1 expression primarily in the hypothalamus; and 3) there is correlation between NR1 expression in pons and medulla with ventilatory parameters.     

A developmental switch affecting growth of fatty rats

Fatty (fa/fa) rats accumulate more adipose mass than their littermates soon after birth, but they first appear obese during the fourth week of life. We analyzed the effects of fa genotype on growth of pups housed with their dams through 4 wk of age. The fa genotype effects on daily gain were undetectable from 7 to 22 days of age but became highly significant (P = 10(-18)) at 23 days of age. When litters were reduced to 4 pups, fa genotype effects on daily gain also became detectable at 23 days of age. The fa genotype effects on daily gain, stomach contents weight, liver weight, and plasma insulin of rats killed from 20 to 24 days of age displayed a marked genotype by age interaction, becoming highly significant at 23 days of age. These changes occur without the environmental changes induced by separating pups from their dams. These observations suggest that a developmental switch triggers hyperphagia and rapidly increases growth rate of fatty rats after 22 days of age.     

Social suppression of female reproductive maturation and infanticidal behavior in cooperatively breeding Mongolian gerbils

In several cooperatively breeding species, reproductively suppressed, nonbreeding females are attracted to infants and routinely provide alloparental care, while breeding females may attack or kill other females' infants. The mechanisms underlying the transition from alloparental to infanticidal behavior are unknown. In this study, we tested the hypothesis that this transition is associated with cessation of reproductive suppression and onset of ovarian activity in the Mongolian gerbil (Meriones unguiculatus), a cooperatively breeding rodent. Young female gerbils were housed with their natal family (FH), with a female pairmate (PH) or singly (SH). When females were either 11-13 or 16-18 weeks of age, we characterized their behavioral responses to an unfamiliar pup, reproductive development, and plasma progesterone, cortisol, and prolactin concentrations. In both age groups, FH females were significantly less likely to attack pups than PH or SH females and in fact never did so. FH females also had smaller ovaries and uteri, less developed scent glands, and lower progesterone levels, and were more likely to be anovulatory than PH or SH females, especially in the 11- to 13-week-old age group. Prolactin concentrations did not differ with reproductive status but were significantly higher in females that did not attack pups than in those that did. We found no other significant associations, however, between reproductive or endocrine measures and behavioral responses to pups. These results suggest that cohabitation with the natal family inhibits both infanticidal behavior and reproductive maturation in young female gerbils but that these two effects may not be causally related.     

棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动

本文运用免疫组化显示Fos蛋白的方法首次研究了棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动。当不同年龄阶段的幼鼠同时暴露于自己家庭的熟悉底物和另一家庭的陌生底物时 ,嗅闻和呆在自己熟悉底物上的时间较多 ,直到产后 15d、 2 0d和 2 5d时 ,幼鼠探究不同底物的行为显示出显著性差异。脑的大小随着日龄增加而增加 ,但从产后 1到 15d ,脑重、脑宽和嗅球大小随着日龄增加特别显著。当不同日龄幼鼠暴露于陌生底物或者暴露于自己的熟悉底物时 ,从产后 5到 15日龄 ,主嗅球僧帽细胞层、颗粒细胞层、副嗅球僧帽细胞层和颗粒细胞层Fos免疫阳性细胞随着日龄明显增加 ,但直到 15和 30日龄时 ,和对照组相比 ,陌生底物可引起幼鼠主嗅球Fos免疫阳性细胞明显增加 ,从 2 0日龄起 ,陌生底物可引起副嗅球Fos免疫阳性细胞明显增加。主嗅球颗粒细胞层Fos免疫阳性细胞随着日龄的增加从边缘到中心逐渐出现 ,而副嗅球Fos免疫阳性细胞随着日龄的增加从顶部到底部逐渐出现。以上结果说明产后第 1d到 15d左右可能是棕色田鼠脑结构发育的重要阶段 ,而从此以后棕色田鼠主嗅球和副嗅球就具有区别熟悉气味和陌生气味的能力 ,表明棕色田鼠行为、脑发育和细胞活动间有紧密关系