Comparative study on isolation calls emitted from hamster pups.

Waveforms of isolation calls emitted from hamster pups, which were Syrian hamsters, Djungarian hamsters, and Chinese hamsters, were compared in a basic study on improving reproduction by decrease of cannibalism, because it was reported that maternal behavior was induced by isolation calls in rodents. Isolation calls of hamster pups, isolated from their mother and receiving cold stress, were collected by Real-Time Spectrogram (RTS), and calculated to spectrograms and power spectra by SIGNAL. Isolation calls consisted of ultrasonic vocalizations (USVs) and audible vocalizations (ADVs) in each species. Waveforms of isolation calls emitted by the hamster pups, were shown to have several characteristic features. In this study, the species specificity of isolation calls was shown in hamster pups. It would seem that the species specificity originates in the differences of sensitivity to cold stress via the autonomic nerve in hamsters.     

新生期触觉刺激和母婴分离对雌性大鼠成年后的焦虑和情绪记忆的影响

采用split-litter法对仔鼠进行分组和处理,共5组NTS组(未经实验人员抓握和标记),PND2—9TS组和PND10—17TS组(分别在仔鼠出生后的2—9天、10—17天,每天短暂抓握和标记仔鼠),PND2—9MS组和PND10—17MS组(分别在仔鼠出生后的2—9天、10—17天,除了按TS组相同方式抓握并在不同部位标记外,每天把仔鼠与母鼠分离1h)。待雌鼠成年后,进行明/暗箱测试和一次性被动回避反应测试。结果发现与NTS组相比,PND2—9TS组和PND10—17TS组的雌鼠在明/暗箱测试中停留于明室的累计时间明显较长,在被动回避作业中的重测试潜伏期也明显较长,表明新生期的触觉刺激经历减少雌性大鼠成年后在新异环境中的焦虑,并改善情绪记忆。与相应TS组相比,MS处理组的所有行为指标都无显著性差异,说明短时间母婴分离对雌鼠成年后的焦虑和情绪记忆无明显影响。结果提示,新生期的触觉刺激和母婴分离经历对仔鼠神经系统的发育产生不同的长期效应。     

The influence of tactile stimulation of nipples on the milk ejection reflex in the rat

Summary Changes of positive pressure exerted by pups on nipples during sucking were investigated using anesthetized, lactating dams. It was found that, every 50–60 s, individual pups performed bouts of pressure oscillations (3/s) of high amplitude which lasted about 10–12 s and coincided with periods of increased motor activity. During the intervals, when pups were quiet, series of low-amplitude oscillations (3/s) were also observed. Using a strain measuring method to record the activity of sucking pups, synchronization of activity of two or more pups was found to occur periodically every 25–30 s and, most frequently, 10–30 s before the reflex increase of milk pressure. In further experiments, artificial tactile stimulation was applied to the dam's nipples using the joint action of suction and positive pressure. Following a short-term (10–20 s) increase in frequency and amplitude of artificial nipple stimulation, 60%–80% of all reflexive peaks of milk pressure were elicited with a latency of 19 ± 5 s. This suggests that there are specific conditions under which the stimulation of nipples by pups may trigger the formation of the milk ejection reflex in the rat.Abbreviation MER milk ejection reflex     

Nocturnal surges and reflexive release of prolactin in parentally behaving virgin female and male rats

Maternally behaving virgin rats are capable of releasing prolactin reflexively in response to stimulation by pups, especially during the proestrous/estrous phase of the cycle. When such rats are chronically exposed to pups they usually undergo a state of pseudopregnancy during which prolactin is secreted in a pattern of nocturnal surges. The present series of experiments evaluated the initiation of nocturnal prolactin surges in maternally behaving virgins, the role of estrogen in the reflexive release of prolactin, and the influence of gender on these two modes of prolactin secretion. It was found that the nocturnal surges of prolactin are already present on Days 1 and 2 of pup-induced pseudopregnancy. At this stage, however, the surges are not yet autonomous, seeing that pseudopregnancy is interrupted shortly after removal of the pups on Day 2. Activation by vaginocervical stimulation of the "mnemonic" neurogenic system that controls the autonomous nocturnal prolactin surges did not interfere with the reflexive pup-induced release of prolactin in maternally behaving virgins. The capacity of reflexive prolactin release in the virgin rat was abolished by ovariectomy, restored by estrogen replacement, and persisted for only 24 hr following estrogen removal. Paternally behaving males subjected to chronic exposure to pups were incapable of secreting nocturnal surges of prolactin characteristic of the pseudopregnant female. Such males were also incapable of releasing prolactin reflexively in response to stimulation by pups, even when supplemented with exogenous estrogen. These results indicate that the two modes of prolactin secretion are sex dependent, and that the maternally behaving virgin, unlike the postpartum rat, requires concurrent estrogenic facilitation for releasing prolactin in response to stimulation by young.     

人为疼痛刺激下金色中仓鼠幼鼠叫声的发育过程

金色中仓鼠幼鼠可以利用可听声和超声信号与母鼠进行交流,这些声音可以反映个体的寒冷、饥饿、疼痛等不同生理状态和需求。因疼痛诱发的叫声对于维持幼鼠的存活也有着重要意义。本实验通过录制人为疼痛刺激下,不同日龄金色中仓鼠的叫声,分析并比较了5 - 30 日龄金色中仓鼠不同发声信号特征(可听声出现频次、可听声持续时程、可听声主频率、超声出现频次、超声持续时程、超声主频率)的性别差异;同时记录了幼鼠的两种发声随日龄的变化趋势。结果发现:幼鼠两种叫声的各种参数均未表现性二型现象。幼鼠超声发生频次随日龄增加而逐渐减少。而可听声却正相反,随日龄增加而逐渐上升,并在20 日龄时达到最高峰,之后逐渐下降。可听声持续时程也随日龄而增加。综上,在人为疼痛刺激下,随着日龄增加,幼鼠更倾向于使用可听 声而非超声与母兽进行交流。     

Mammary stimulation and maternal aggression in rodents: thelectomy fails to reduce pre- or postpartum aggression in rats

In mice, tactile stimulation of the nipples appears to be critical for the onset of postpartum maternal aggression. Surgical removal of the nipples (thelectomy) blocks aggression if performed prior to parturition. In rats, indirect evidence suggests a similar role for nipple stimulation in maternal aggression. Two experiments were undertaken to determine whether thelectomy prior to mating reduces pregnancy-induced and/or postpartum aggression in this species. In the first, thelectomized and sham-thelectomized females were subjected to home cage tests (pups, if any, present) with unfamiliar male intruders on Gestation Days 18 and 21 and Lactation Days 3 and 5. Additional groups of thelectomized females were tested one time only on either Lactation Day 5 or 12. Thelectomized and control females were equally aggressive; postpartum, nearly all females in both groups attacked. Experiment 2 used females that were hysterectomized-ovariectomized (HO) on Gestation Day 16. Such females are not aggressive prior to initiating maternal behavior, but become highly aggressive (over 80% attacking) after commencing maternal care. Females again were thelectomized or sham-thelectomized prior to mating. On Day 16 HO was performed, and 48 hr later continuous exposure to pups was begun. After the females had displayed maternal behavior for 1.5-2 days, intruder tests were conducted. All females attacked at least once, with no differences between treatment groups. Thus thelectomy does not reduce maternal aggression in the rat. This finding, however, does not preclude a role for tactile ventral stimulation in mediating maternal aggression.     

Interactions of partners in family pairs,care of the offspring,and the role of tactile stimulation in formation of parental behavior of the Mongolian gerbil (<Emphasis Type="Italic">Meriones unguiculatus</Emphasis>) under laboratory conditions

The interactions of sexual partners and care of the offspring in male and female Mongolian gerbils reared in biparental and uniparental family groups (without an adult male) were compared. In individuals reared in biparental family groups, sexual differences related to the manifestation of parental care were small and statistically insignificant. In individuals reared in uniparental groups, the interactions of sexual partners related to grooming changed; the duration in males decreased threefold, as compared to the norm; indices of parental behavior of females and, especially of males, related to tactile stimulation of pups (huddling with pups in the nest and duration of licking pups) also decreased. The importance of the parental contribution of males, especially of tactile stimulation, in the evolution of the family-group mode of life is discussed.     

Disruption of ATP homeostasis during chronic cold stress and recovery in the chill susceptible beetle (Alphitobius diaperinus)

This study examined the impact of fluctuating thermal regimes (FTRs) on cold tolerance of the polyphagous beetle Alphitobius diaperinus. Daily pulses of elevated temperatures can provide breaks in chronic cold stress, potentially allowing for physiological recovery and improving survival. Perturbations in central metabolism appear to be a common physiological response in insects exposed to low temperatures. It has been suggested that energy supplies, which may be depleted during cold exposure, can be regenerated during the warming pulses of FTRs. This study tested the assumption that chronic cold stress may induce ATP depletion and that recovery during FTR warming pulses may allow re-establishment of ATP supplies. In this study, A. diaperinus were exposed to cold stress under different thermal regimes (constant or fluctuating). The results did not confirm the aforementioned assumption. No cold-induced ATP depletion was observed. The lowest ATP levels were repeatedly detected in the untreated controls. The data show that homoeostasis of ATP is lost when adults A. diaperinus are exposed to cold stress, whatever thermal regime (constant or fluctuating). ATP accumulation may be viewed as a symptom of a production/consumption imbalance under cold stress conditions. Periodic short (2-h) warming pulses clearly improved cold survival. Cellular homeostasis, however, probably requires a longer recovery period to be fully restored.     

Ultrasonic isolation calls in genetically high- and low-emotional rat pups.

The present study was undertaken to investigate the relationship between the emotionality and the modulation of ultrasonic vocalizations in Tsukuba High Emotional (THE) and Tsukuba Low Emotional (TLE) strain rat pups 3-18 days old. The THE pups, while isolated from their dam and littermates and placed in a cold environment, emitted ultrasonic isolation calls at a high rate until day 15. In contrast, ultrasound production was at a consistently low level throughout the test period in the TLE pups. The ultrasonic isolation calls of THE pups were attenuated to the same level as those of the TLE pups after administration of diazepam (1 mg/kg, s.c.), a benzodiazepine receptor agonist, at 6 and 12 days of age. These findings suggest that the high emotionality of the rat pups was reflected largely by the emission of ultrasounds in response to isolation distress rather than the number of the benzodiazepine receptors in the brain that might play a role in physiologic mediation of the rat pup isolation call.     

Neural and hormonal control of arterial pressure during cold exposure in unanesthetized week-old rats

Infant rats respond to cold exposure with increased heat production by brown adipose tissue (BAT). BAT thermogenesis increases steadily with increasing cold exposure, but a point occurs at which thermogenesis can increase no further, resulting in cold-induced bradycardia. Previous work has shown that mean arterial pressure (MAP) is maintained even when cardiac rate decreases as much as 50% from baseline values. We examined the neural and hormonal contributions to peripheral resistance during cold exposure after pups were injected subcutaneously with vehicle, an alpha1-adrenoceptor antagonist (prazosin; 0.5 mg/kg), an ANG II receptor antagonist (losartan; 1 mg/kg), a vasopressin receptor antagonist (Manning compound; 0.5 mg/kg), or simultaneous administration of all three antagonists (triple block). Interscapular temperature, oxygen consumption, cardiac rate, and arterial pressure were monitored as air temperature was sequentially decreased from thermoneutral (i.e., 35 degrees C) to 29, 23, and 17 degrees C. Only pups in the triple block condition exhibited significant decreases in MAP with cooling, even though all pups exhibited substantial decreases in cardiac rate. A followup study suggested that blockade of all three systems was more effective than blockade of any two systems. Finally, at 17 degrees C, ultrasonic vocalizations were accompanied by significant increases in MAP, replicating a previous finding and supporting the hypothesis that the vocalization is the acoustic by-product of the abdominal compression reaction, a maneuver that helps to maintain venous return during cardiovascular challenge.     

Neuroethology of olfactory preference development.

Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training.     

Neuroethology of olfactory preference development

Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training. © 1992 John Wiley & Sons, Inc.     

The ultrasonic responses of albino mouse pups to tactile stimuli

Tactile stimuli, like environmental temperature changes, can evoke ultrasonic responses from albino mouse pups. But the changes with age in the intensity of ultrasounds so produced follow a different pattern from those due to temperature changes. The responses begin with very high intensity pulses in the very young pups and then gradually decline with the age of the pups. The present report arises from a systematic study of this phenomenon, the results of which are discussed in relation to those of previous ones.     

Positive effects of tactile versus kinesthetic or vestibular stimulation on neuroendocrine and ODC activity in maternally-deprived rat pups

Previous studies in our laboratory have shown that even short-term separation of preweanling rat pups from the mother produces adverse effects in the pup. These include alterations in ornithine decarboxylase activity and in the secretion of growth hormone and corticosterone. The present study demonstrates that while intermittent heavy stroking effectively reverses or prevents all the changes associated with maternal deprivation neither kinesthetic nor vestibular stimulation affects these responses. The results verify earlier findings from this laboratory indicating that tactile interactions between rat pups and their mother modulate pup physiology and provide experimental support for the hypothesized role of tactile stimuli on early infant development.     

Maternal care effects on SNB motoneuron development: The mediating role of sensory afferent distribution and activity

Maternal licking in rats affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Reduced maternal licking produces decreased motoneuron number, size, and dendritic length in the rostral portion of the adult SNB as well as deficits in adult male copulatory behavior. Previous research suggests that decreases in perineal tactile stimulation may be responsible for these effects. To determine whether the regional effects of maternal licking on SNB morphology are driven by sensory afferent innervation of the lumbosacral spinal cord, we used WGA‐HRP to reconstruct the location of sensory afferent fibers from the perineal skin. We found that these fibers are caudally concentrated relative to the area of the SNB dendritic field, with the rostral dendritic arbor receiving little perineal afferent innervation. We also assessed Fos expression following perineal tactile stimulation to determine whether it increased local spinal cord activity in the SNB dendritic field. Sixty seconds of licking‐like perineal stimulation produced a transient 115% increase in Fos expression in the area of the SNB dendritic field. This effect was driven by a significant increase in Fos in the caudal portion of the SNB dendritic field, matching the pattern of perineal afferent fiber labeling. Perineal tactile stimulation also produced significantly greater Fos expression in male pups than in female pups. Together, these results suggest that perineal sensory afferent activity mediates the effects of early maternal care on the masculinization of the SNB and resultant male copulatory behavior. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009     

Circadian Adrenocortical Periodicity Changes in Adult Rats Stimulated During Early Development—II. Effect of Cold Stress

Rats were cooled at different time points of early postnatal development to study the effects of short-term stress on the parameters of the circadian rhythm of the adrenocortical function in adults. It was found that rats stressed at the age of 2-4 or 17-19 days exhibit modified tuning in the circadian periodicity of the adrenocortical function as adults. Cold stimulation during early development does not affect the function of isolated adrenal glands in vitro. It is concluded that the effect of early stress on the adrenocortical rhythmicity in adults is mediated through central regulatory mechanisms. This effect depends on the age when the rat pups are exposed to cold stress.     

Circadian Adrenocortical Periodicity Changes in Adult Rats Stimulated During Early Development—II. Effect of Cold Stress

Rats were cooled at different time points of early postnatal development to study the effects of short-term stress on the parameters of the circadian rhythm of the adrenocortical function in adults. It was found that rats stressed at the age of 2-4 or 17-19 days exhibit modified tuning in the circadian periodicity of the adrenocortical function as adults. Cold stimulation during early development does not affect the function of isolated adrenal glands in vitro. It is concluded that the effect of early stress on the adrenocortical rhythmicity in adults is mediated through central regulatory mechanisms. This effect depends on the age when the rat pups are exposed to cold stress.     

To stay or not to stay: the contribution of tactile and thermal cues to coming to rest in newborn rabbits

Newborn rabbits, like other altricial mammals, demonstrate thermotaxis and when placed on a thermal gradient locate and come to rest at physiologically appropriate temperatures. Little is known, however, about the sensory-motor components contributing to the in energetic terms important decision of the young to cease locomotion and come to rest. We investigated the behavior of newborn rabbits on two thermal gradients; linear in which pups could use tactile cues from the arena wall, and concentric in which pups were unable to use such cues. On both gradients pups located the warm, thermal-neutral area within the 200-s test time, thereby demonstrating their ability to orient appropriately using thermal cues alone. Unexpectedly, however, pups on the concentric gradient failed, or took significantly longer, to come to rest than pups on the linear gradient. Since the speed of locomotion of pups on the linear gradient was significantly slowed when they were in contact with the arena wall, and in most cases they came to rest in contact with it, we suggest that not only thermal but also tactile cues may be important in bringing young mammals to rest in a thermally appropriate environment.     

Tactile stimulation during artificial rearing influences adult function and morphology in a sexually dimorphic neuromuscular system

Maternal licking of rat pups affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneurons, with reductions in licking producing decreased SNB number, size, and dendritic length in adulthood. Reduced maternal licking also produces deficits in adult male copulatory behavior. In this experiment, we used an artificial rearing paradigm to assess the potential role of tactile stimulation in mediating the effects of maternal licking on the SNB neuromuscular system. During artificial rearing, pups were stroked with a paintbrush to mimic maternal licking, receiving low, medium, or high levels of daily stimulation. In adulthood, ex copula penile reflex behavior was tested and the morphology of SNB motoneurons assessed. SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP and dendritic arbor was reconstructed in three dimensions. Animals that received low levels of stimulation showed deficits in penile reflexes relative to maternally reared controls, including a longer latency to erection, fewer cup erections, and fewer erection clusters. SNB dendritic morphology was also shaped by stimulation condition, with animals that received low or medium levels of stimulation showing an average 27% reduction in dendritic length. In addition, several reflex behaviors were significantly correlated with dendritic length, including latency to first erection, percent of cup erections, and number of erection clusters. These results suggest that tactile stimulation provided by maternal licking mediates some of the effects of maternal care on the development of male copulatory behavior.     

Accumbal dopamine function in postpartum rats that were raised without their mothers

Postpartum rats that had been previously raised in an artificial rearing (AR) apparatus, without their mothers or siblings during the preweaning period, show altered maternal responses towards their own offspring in adulthood. In mother-reared (MR) rats, nucleus accumbens (NAC) dopamine (DA) responses to pups evoke a robust sustained rise during the postpartum period and following treatment with estrogen/progesterone parturient-like hormones (Afonso et al., 2009). These MR females had siblings that received AR rearing with varying amounts of preweaning tactile stimulation (ARmin; ARmax). The present study examined NACshell DA responses to pup and food stimuli in these AR rats, and statistically compared them to their MR siblings. Microdialysis samples were collected from adult (90 days postnatal) AR females in different parity states (cycling vs. postpartum, Exp. 1), or after ovariectomy with different hormone treatments (sham vs. hormone, Exp. 2. After basal sample collection, pup and then food stimuli were individually presented to the females in the dialysis chamber. As with their MR siblings, basal DA concentrations were lower and pup-evoked DA responses greater in hormonally-primed AR females than in non-primed AR controls. Compared to their postpartum MR sisters (Exp. 1), AR rats had increased basal DA levels, reduced pup related DA elevations, and disrupted maternal behavior. The postpartum AR impairment in pup-evoked DA was reversed by additional pre-weaning tactile stimulation. Exogenous hormones (Exp. 2) eliminated AR impairments on pup-evoked DA responses. Although MR and AR siblings had comparable DA responses to food stimuli, upon reanalyzing MR data it was found that only postpartum dams had DA responses to pups greater than to food. These data suggest that that the hormonally induced suppression of basal DA levels may reflect saliency of pups which was greater in MR than in AR dams. Preweaning tactile stimulation could partially reverse these effects only in naturally cycling or parturient animals.