Changes In Maternal Behavior Research Articles

Measuring infant response to early adverse events in the mouse

Event Abstract Back to Event Measuring infant response to early adverse events in the mouse Francesca R. D-Amato1*, Carlo Cinque1, Valentina Lampis2, Diego Oddi1, Claudio Zanettini1 and Anna Moles1 1 CNR Institute for Neuroscience, Italy 2 San Raffaele University, Italy The role of early environment in affecting vulnerable genotypes and precipitating psychopathologies during development and in adult life has been well documented in humans. Animal models of adverse life experiences have been established using pre and/or postnatal stressful events. Maternal behaviour during the early postnatal days has been analysed in details as possible mediator of the long lasting behavioural and physiological responses in the adult offspring. Contrary to rat, mouse maternal behaviour seems less flexible and less responsive to stressed-pups’ requests. This absence of changes in maternal behaviour in mice also when facing a challenging environment could be due to low pups responsiveness to the stress procedure, to low maternal responsiveness to stressed pups, or to a more general disruption of mother-infant relationship. While maternal behaviour has been extensively studied, infant’s behaviour offers fewer possibilities of investigation, due to the immaturity of the pup at birth. However, both the olfactory and the ultrasound communicatory systems are already functional in pups to build and establish the attachment bond with the caretaker. The analysis of the mother-infant bond, from the pup´s “viewpoint”, will be performed in response to different postnatal environmental and/or pharmacological treatments. Ultrasonic vocalizations in response to isolation, olfactory discrimination and attraction by nest/mother cues will be used as measures of infant attachment bond during development. This approach could shed light on long-term disruptive effects of neonatal stressful treatment in mice when no apparent changes in maternal behaviour occurred. Conference: 41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: D-Amato FR, Cinque C, Lampis V, Oddi D, Zanettini C and Moles A (2009). Measuring infant response to early adverse events in the mouse. Conference Abstract: 41st European Brain and Behaviour Society Meeting. doi: 10.3389/conf.neuro.08.2009.09.126 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Jun 2009; Published Online: 08 Jun 2009. * Correspondence: Francesca R D-Amato, CNR Institute for Neuroscience, Rome, Italy, francesca.damato@cnr.it Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Francesca R D-Amato Carlo Cinque Valentina Lampis Diego Oddi Claudio Zanettini Anna Moles Google Francesca R D-Amato Carlo Cinque Valentina Lampis Diego Oddi Claudio Zanettini Anna Moles Google Scholar Francesca R D-Amato Carlo Cinque Valentina Lampis Diego Oddi Claudio Zanettini Anna Moles PubMed Francesca R D-Amato Carlo Cinque Valentina Lampis Diego Oddi Claudio Zanettini Anna Moles Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Why has the health inequality among infants in the US declined? Accounting for the shrinking gap

Given that wealthier people are healthier, the increase in income inequality over the past two decades has led to fears that inequalities in health have also increased. Indeed, some papers have found that health disparities have become more salient among some adult populations. Using the US Vital Statistics 1983-2000, this paper presents a new stylized fact: the infant health disparity, as measured by Apgar score, neonatal mortality and infant mortality, has been narrowing over the past two decades. This is in sharp contrast to the increasing disparities in health among adults of different educational backgrounds. Using a decomposition method, I find that the most important factor in explaining the closing gap is an increase in access to medical care. All else being equal, access to proper medical care is the most important factor in explaining the narrowing infant health gap. Demographic shifts and maternal behavior changes are also significant factors, together explaining 42.2% of the closing gap in low Apgar score, 41.4% of the closing gap in neonatal death, and 45.6% of the closing gap in infant death.

Naturally occurring variations in maternal care modulate the effects of repeated neonatal pain on behavioral sensitivity to thermal pain in the adult offspring

Repeated pain during a critical period of development can have long-term behavioral and physiological consequences in both human and animals. We previously showed that rat mothers caring for pups subjected to mild pain in neonatal life increased pup licking and grooming behavior. Therefore, we tested whether naturally occurring variations in maternal behavior would modulate the effects of repeated mild inflammatory pain on behavioral responses to pain and stress in the adult male offspring. Rat pups were either uninjected (UI) or injected twice daily between PND3 and PND14 with either saline (0.9%) or formalin (0.2–0.4%) in the footpad of the hindpaw. Maternal behavior (pup licking and grooming) was recorded under basal conditions and after reunion with the litter post injection to determine maternal phenotype (High, Middle, Low licking). Adult offspring (PND60) were tested for their thermal sensitivity, inflammatory pain responses after formalin injection and neuroendocrine responses to formalin injection. Maternal phenotype significantly altered pain sensitivity after thermal stimulation, but not formalin injection. Offspring from the High licking mothers displayed increased withdrawal latencies compared to offspring from Low mothers, regardless of neonatal treatment. Pain responses after formalin injection were higher in offspring receiving formalin as neonates compared to saline-treated or uninjected rats, demonstrating a long lasting increased sensitivity to inflammatory pain. Neuroendocrine responses to pain stress were not affected by neonatal treatment. These data suggest that changes in maternal behavior can influence some modalities of pain sensitivity and that repeated mild inflammatory pain in neonatal period causes hypersensitivity to formalin in the adult offspring.

Preventing Mother-to-Child HIV Transmission Among South African Adolescents

Although prevention of mother-to-child HIV transmission (PMTCT) programs are predicated on maternal behavior change, little is known about sociocultural factors affecting maternal—child care practices in this arena. The authors used narrative methods (key informant workshops, questionnaires, focus groups, and case study analysis) to explore how sociocultural context shapes adolescent mothers' ability to adhere to programmatic recommendations in rural and urban South Africa. The study aims were to understand the extent to which mothers' decisions are borne out in PMTCT-related practices and to identify contextual elements that affect the link between individual resolutions and action. The results revealed rural adolescents as less likely than urbanites to successfully implement most PMTCT-related practices. HIV stigma, family decision making, and cultural norms surrounding infant feeding hampered mothers' efforts to implement practices that would decrease the risk for infant infection. Barriers to behavior change were analyzed along four domains: history, culture, gender, and power. Methodological aspects and programmatic implications are discussed.

Effect of 2,4-dichlorophenoxyacetic acid on rat maternal behavior

Exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) has several deleterious effects on the nervous system such as alterations in the concentrations of neurotransmitters in the brain and/or behavioral changes, myelination rate, ganglioside pattern [Bortolozzi, A., Duffard, R., Antonelli, M., Evangelista de Duffard, A.M., 2002. Increased sensitivity in dopamine D(2)-like brain receptors from 2,4-dichlorophenoxyacetic acid (2,4-D)-exposed and amphetamine-challenged rats. Ann. N.Y. Acad. Sci. 965, 314-323; Duffard, R., García, G., Rosso, S., Bortolozzi, A., Madariaga, M., DiPaolo, O., Evangelista de Duffard, A.M., 1996. Central nervous system myelin deficit in rats exposed to 2,4-dichlorophenoxyacetic acid throughout lactation. Neurotoxicol. Teratol. 18, 691–696; Evangelista de Duffard, A.M., Orta, C., Duffard, R., 1990. Behavioral changes in rats fed a diet containing 2,4-dichlorophenoxyacetic butyl ester. Neurotoxicology 11, 563–572; Evangelista de Duffard, A.M., Bortolozzi, A., Duffard, R.O., 1995. Altered behavioral responses in 2,4-dichlorophenoxyacetic acid treated and amphetamine challenged rats. Neurotoxicology 16, 479–488; Munro, I.C., Carlo, G.L., Orr, J.C., Sund, K., Wilson, R.M. Kennepohl, E. Lynch, B., Jablinske, M., Lee, N., 1992. A comprehensive, integrated review and evaluation of the scientific evidence relating to the safety of the herbicide 2,4-D. J. Am. Coll. Toxicol. 11, 559–664; Rosso et al., 2000], and its administration to pregnant and lactating rats adversely affects litter growth and milk quality. Since normal growth of the offspring depends on adequate maternal nursing and care, we evaluated the effect of 2,4-D on rat maternal behavior as well as the dam's monoamine levels in arcuate nucleus (AcN) and serum prolactin (PRL) levels. Wistar dams were exposed to the herbicide through the food from post partum day (PPD) 1 to PPD 7. Dams were fed either with a 2,4-D treated diet (15, 25 or 50 mg 2,4-D/kg/day bw) or with a control diet. We observed that maternal nesting behavior was not modified by 2,4-D treatment. However, mother–pup interactions, specially the nursing behavior, were altered. Retrieval, crouching and licking of pups were reduced or suspended after 2,4-D treatment. We also observed an increase in the latency of retrieval and crouching in the dams treated with the herbicide. Dams showed movement along cage peripheries, food consumption during the light phase and high self-grooming. In addition of the deficits observed in maternal behavior parameters, increased catecholamine levels and a drastic decrease in indolamine levels in the AcN of treated dams were determined. Serum PRL levels were also diminished by 62%, 68% and 70% with respect to control dams in the 15, 25 and 50 mg 2,4-D/kg bw treated dams, respectively. In conclusion, exposure to 2,4-D during the first post partum days produced changes in maternal behavior, serum prolactin and monoamine levels in the AcN of treated dams.

Experience-dependent cell survival in the maternal rat brain.

Postpartum maternal experience produces long-lasting changes in maternal behavior in the mother rat, which can be altered by early-life isolation. Postpartum experience also affects the regulation of adult neurogenesis in the neural circuit underlying maternal behavior, in a region-specific manner. Female rats were reared either with their mothers (MR) or in isolation in an artificial rearing (AR) paradigm. In adulthood, rats were mated and separated from their pups at birth. The following day, dams were injected with a mitotic marker and either allowed to interact with pups (maternal experience) or left alone. Results show that MR rats that acquire a later maternal experience show increases in cell survival in parts of the excitatory limb of the maternal neural network (bed nucleus of the stria terminalis and nucleus accumbens), but no changes in the inhibitory limb (amygdala). In comparison to AR inexperienced rats, AR maternally experienced rats show no increases in cell survival in the excitatory limb, but a striking reduction in cell survival in the inhibitory limb. The results suggest that early preweaning maternal isolation alters the structural plasticity that occurs following a postpartum maternal experience.

Early behavioural enrichment in the form of handling renders mouse pups unresponsive to anxiolytic drugs and increases NGF levels in the hippocampus

Early life experiences, such as early handling, can influence neural development of rodents leading to changes in physiological and behavioural reactivity to stress. These effects are likely to be mediated by changes in maternal behaviour. This study analyzed the effects of different manipulations of the rearing environment on maternal behaviour and the behavioural and physiological response to mild challenges in CD-1 mouse pups early during development. Litters underwent either 15 min of neonatal handling (H) or were exposed briefly to an unfamiliar male intruder from postnatal (PND) days 2 to 14 (MI). Both groups were compared with litters which were not manipulated (NH). Compared to NH subjects, licking behaviour in the MI group was increased only on the first day of introduction of the male intruder, while the H group showed an increase in maternal behaviour on PND 10. On PND 8, pups ultrasonic vocalizations were recorded upon treatment with an axiolytic drug (chlordiazepoxide 0, 2, or 7.5 mg/kg). Results indicate that, although there were no differences among the groups when mice were injected with vehicle, handled subjects did not reduce their calling rate following drug administration, in contrast to the NH and MI groups. Following maternal separation and novelty exposure on PND 9, levels of hippocampal NGF increased significantly only in the H group. These data suggest that active pup manipulations in the form of handling favour behavioural and neural plasticity resulting in the maintenance of a high level of arousal and in increased neurotrophin levels in response to an acute manipulation. Changes in hippocampal levels of NGF might be involved in the appraisal of subtle changes in the early social environment.

Psychological stressors as a model of maternal adversity: Diurnal modulation of corticosterone responses and changes in maternal behavior

Maternal adversity is associated with long-lasting consequences on cognitive development, behavior and physiological responses in rat offspring. Few studies have examined whether repeated maternal stress produces repeated activation of the hypothalamus–pituitary–adrenal (HPA) axis in mothers and whether it modifies maternal behavior. Here, we tested a novel model of perinatal stress using repeated exposure to “purely” psychological stressors throughout the gestation and lactation periods in rats. We first tested the diurnal influences of repeated 1-h strobe light exposure on maternal corticosterone secretion. Despite the hyporesponsiveness to stress documented in late pregnant and lactating mothers, we observed an enhanced response to strobe light in the afternoon compared to the morning in stressed mothers during lactation. Next, dams were exposed to 24-h forced foraging followed by 10-h wet bedding during the diurnal peak of corticosterone secretion. Although no corticosterone responses to forced foraging and wet bedding were observed, the combination of both stressors had a significant effect on maternal behavior. Mother–pup interactions were significantly altered during the first 8 days of lactation. Taken together, these findings suggest that lactating mothers maintain responsiveness to specific and repeated psychological stressors, in particular at the time of the diurnal peak in corticosterone secretion. Depending on the stressor applied, either neuroendocrine activation or changes in maternal behavior might be important determinants of the long-term consequences in the offspring. The combination of forced foraging, wet bedding and strobe light might represent a novel model of mild maternal adversity using “purely” psychological stressors.

Evidence for non‐genomic transmission of ecological information via maternal behavior in female rats

Maternal behavior is flexible and programs offspring development. Using a novel manipulation, we demonstrate that rat maternal behavior is sensitive to ecologically relevant stimuli. Long-Evans hooded rat dams (F0) and pups were exposed to a predator condition (cat odor) or a control condition (no odor) for 1 h on the day of parturition. Predator-exposed F0 dams displayed significantly more maternal behavior (licking/grooming, arched-back nursing) relative to control-exposed dams across five subsequent observation days. Female offspring (F1) were raised to adulthood, bred and maternal behavior was observed. F1 dams reared by a predator-exposed F0 dam displayed significantly higher maternal behavior relative to F1 dams reared by a control-exposed F0 dam across 5 days of observation. Increased levels of maternal behavior in predator-reared (PR) F1 dams were evident even in F1 females that had been cross-fostered (CF) from a control-exposed F0 dam, suggesting a non-genomic transmission of increased levels of maternal behavior. Lactating PR F1 dams had significantly elevated estrogen receptor alpha and beta mRNA in the medial preoptic area relative to control-reared (CR) F1 dams. Furthermore, among CR F1 dams, there was no significant difference between those dams that had been CF from predator-exposed F0 dams and those that had been sham CF. These results support the hypothesis that flexible rat maternal behavior can shape offspring development according to current environmental conditions. The results also suggest that estrogen signaling may be part of an epigenetic mechanism by which changes in maternal behavior are passed from F0 to F1 dams.

Methods in the Analysis of Maternal Behavior in the Rodent

The aim of this unit is to provide a set of fundamental protocols to assess maternal behavior in rats and mice. Parental behavior in rodents is characterized by a rather complex set of behavioral items, which are described in great detail. A special emphasis has been placed on listing the many intervening variables that can bias the correct assessment of maternal behavior and the modifications to that behavior resulting from exposure to drugs or toxic compounds. Because changes in maternal behavior can be very subtle, the accuracy of the protocols can enhance the likelihood of detecting minor differences in behavior resulting from the experimental procedures. In addition, some suggestions are given on the most appropriate methods of data collection and their statistical analysis.

Effect of neonatal handling and paternal care on offspring cognitive development in the monogamous California mouse ( Peromyscus californicus)

In the laboratory rat and mouse, neonatal handling enhances hippocampal-dependent learning in adulthood, an effect mediated by changes in maternal behavior toward the handled young. In the present study, we examined the interaction between neonatal handling and biparental care during the early postnatal period and its effect on cognitive function in adult California mice ( Peromyscus californicus). We characterized the parental behavior of handled and nonhandled father-present and father-absent families over the first 15 days of life. We then assessed cognitive performance of male and female offspring in the Barnes maze and object recognition test after they were 60 days of age. We found that the amount of licking and grooming received by pups was decreased in father-absent families. By postnatal days 12–15, licking and grooming in handled, father-absent families were equivalent to that of nonhandled, father-present families. Handling enhanced novel object recognition in father-present male mice with no effect in females. In the nonhandled group, the presence of the father had no effect on object recognition learning in male or female mice. Handling also enhanced spatial learning in the Barnes maze. In nonhandled families, the presence of the father appeared to have no effect on spatial learning in the male offspring. Interestingly, spatial learning in nonhandled, father-absent, female offspring was similar to that of handled animals. The average amount of licking and grooming received by pups was negatively correlated with the average number of errors made on the first day of reversal training in the Barnes maze. These data support previous findings that neonatal handling facilitates learning and memory in adulthood, suggest that under certain environmental conditions, there is a sex difference in the response of pups to paternal care, and further demonstrate the importance of active parental investment for offspring cognitive development.

Maternal behavior changes after immune challenge of neonates with developmental effects on adult social behavior.

To examine whether maternal responsiveness during interactions with endotoxin-treated pups contributes to long-term effects on social development, neonatal mice were fostered on postnatal day 1 to dams from three selectively bred lines that differ in social behaviors. On day 5, neonates were administered saline or 0.5 mg/kg endotoxin (lipopolysaccharide, i.p.). Observations of undisturbed dams and litters on days 2, 4, 6, and 8 showed modest line differences in maternal behaviors. At the peak intensity of the transient illness induced by endotoxin (3 hr postinjection on day 5), dams increased licking and decreased time off-nest for endotoxin, but not saline-treated pups. As adults, fostered-reared males were observed in brief social interactions. Males exposed to endotoxin early in life showed changes in adult social behaviors that depended on foster dam line as well as individual differences in maternal responsiveness. Maternal responsiveness to stressed neonates can ameliorate the social-developmental effects of early illness.

Artificial rearing causes changes in maternal behavior and c-fos expression in juvenile female rats.

This study investigated the effects of early-rearing experiences on responsiveness to pups and on the pattern of c-fos activation in the brain of juvenile female rats. From Days 4 to 20, littermate females were reared with their mothers (MR) or artificially (AR). AR rats received minimal licking-like tactile stimulation (AR-min) or maximal stimulation (AR-max). On Day 20, rats were exposed to pups for 4 or 8 days, exposed to a playmate for 4 or 8 days, or left in isolation for 4 or 8 days. Compared with MR rats, pup-exposed AR rats engaged in less pup licking, and all AR rats showed significant reductions in c-fos immunoreactivity in the medial preoptic area and the parietal and piriform cortices. The AR-min group showed the greatest difference in Fos-lir compared with the MR groups. Possible mechanisms that mediate the effects of rearing on the development of neural circuits underlying maternal behavior are discussed.

Artificial rearing causes changes in maternal behavior and c-fos expression in juvenile female rats.

Artificial rearing causes changes in maternal behavior and c-fos expression in juvenile female rats.

Acute cocaine alters oxytocin levels in the medial preoptic area and amygdala in lactating rat dams: implications for cocaine-induced changes in maternal behavior and maternal aggression

Acute cocaine administration has been correlated with disruptions in the onset and maintenance of maternal behavior as well as decreases in maternal aggressive behavior in rat dams. A growing body of evidence suggests that cocaine may alter oxytocin levels leading to impairments in maternal behavior and aggression. The current study assessed whether acute cocaine injections alter oxytocin (OT) levels in the medial preoptic area (MPOA), ventral tegmental area (VTA), amygdala (AMY), and hippocampus (HIP) on postpartum day (PPD) 1 or PPD 6. On PPD 1, 30mg/kg cocaine reduced OT levels by approximately 26.9% (picograms/milligram) in the MPOA (t (18) = 3.44, P<.01) compared to saline. On PPD 6, 30mg/kg cocaine significantly increased OT levels by approximately 20.9% (picograms/brain area) in the AMY (F (2,25) = 3.44, P= .05) relative to saline. These findings suggest that acute cocaine may disrupt maternal behavior and maternal aggression at least in part through its action on the oxytocinergic system.

Chronic Leptin Administration in Developing Rats Reduces Stress Responsiveness Partly through Changes in Maternal Behavior

In adult rodents, leptin has been shown to significantly alter the activity of several neuroendocrine functions, including the activity of the hypothalamic–pituitary–adrenal (HPA) axis. Leptin is generally believed to be inhibitory to HPA activity in adults. Developing rat pups have high circulating levels of leptin, which begs the question of leptin's physiological role in controlling basal and stress-induced adrenocortical activity in neonatal rats. In this study, we treated rat pups daily from days 2–9 (or 6–10) of life with either vehicle or leptin (1 or 3 mg/kg body wt, ip) and determined the effects on body weight gain, fat pad deposits, and HPA activity in 10-day-old pups. We measured hypothalamic CRF mRNA levels in vehicle- and leptin-treated pups by in situ hybridization and determined plasma ACTH, corticosterone, and leptin concentrations under basal conditions or following exposure to a 3-min ether stress. Because leptin activates sympathetic activity and energy expenditure in adults and possibly also in rat pups, and because litter temperature is an important determinant of maternal behavior, we also investigated whether chronic leptin administration would modify aspects of maternal care that are important for the maintenance of HPA function. Chronic leptin treatment increased circulating levels of leptin and had significant dose-related metabolic effects, including reduced body weight gain and fat pad weight in 10-day-old pups. Basal expression of CRF mRNA in the PVN or secretion of ACTH and corticosterone was not modified by leptin treatment. In contrast, chronically elevated leptin concentrations during the neonatal period significantly lowered CRF expression in the PVN 60 min after stress and reduced the duration of the ACTH response to stress in pups, suggesting that glucocorticoid feedback on the HPA axis might be altered by this treatment. In addition, mothers caring for pups injected with leptin displayed longer bouts of anogenital licking of pups than mothers of vehicle-treated rats. Given that this particular type of pup stimulation has been shown to influence stress responsiveness, it is possible that the maternal response modulates the effects of exogenous leptin treatment. In conclusion, our results demonstrate that the leptin signal is functional during the early developmental period and that leptin can modulate the hormonal response to stress in young rats either by a direct effect on the HPA axis or indirectly through changing some aspects of maternal behavior.

Commentary: is maternal stimulation the mediator of the handling effect in infancy?

In a recent report, a series of studies is described showing that individual differences in rat maternal licking and grooming are correlated with their offsprings' later adrenal response to a stressor (Liu et al., 1997). Pups that received more maternal stimulation in infancy had lower ACTH, corticosterone, and CRH mRNA, while they had greater amounts of GR mRNA. Liu et al. also compared maternal behavior in litters where rat pups were handled daily to maternal behavior of nonhandled litters. They found that mothers of handled pups licked and groomed their young significantly more often than did mothers of control litters. In their discussion, Liu et al. proposed that their data support Levine's (1975) thesis that handling effects in infancy are mediated via the mother. Levine had proposed that handling of pups will modify the mother--pup interaction, thereby causing a change in maternal behavior. The purpose of this commentary is to summarize data obtained with mice and rabbits which, in part, support and, in part, challenge the conclusions of Liu et al.

Neuroanatomical basis of maternal memory in postpartum rats: selective role for the nucleus accumbens.

The experience of interacting with pups causes long-term changes in mothers' brains that mediate long-term changes in maternal behavior. As little as 1 hr of pup experience postpartum results in enhanced maternal responses to pups 10 days later. This experiment investigated the effects of lesions in multiple neural sites that have been implicated either in the actual expression of maternal behavior or in learning and memory within other behavioral contexts on the initiation and the long-term experience-based retention of maternal behavior. Electrolytic lesions were performed either before or after a 1-hr or 24-hr maternal experience. Rats sustaining lesions of the nucleus accumbens (NACC), whether administered before parturition and experience or immediately after a brief experience, failed to show a maternal experience effect. NACC lesions sustained 24 hr after a maternal experience did not disrupt long-term retention of the maternal behavior.

Group size, infant development and social networks in free-ranging rhesus monkeys

The hypothesis that demographic processes are important in determining social structure among non-human primates through their effects on the development of individual social relationships was tested. Changes in maternal behaviour, infants’ social milieux and infants’ social networks were examined as a function of changes in group size and composition among free-ranging rhesus monkeys,Macaca mulattaon Cayo Santiago, Puerto Rico. Data were analysed for 10 group-years collected between 1974 and 1990 representing a single social group during periods of rapid expansion and fissioning, two daughter groups following fissioning and an unrelated group that did not undergo fissioning. As group size expanded, infants found themselves near (<5m) larger numbers of group members and smaller proportions of close kin. Mothers spent more time near their infants and sought more proximity with them. Infants developed social networks that were more highly kin biased. When the groups fissioned, these trends reversed. Significant correlations were found between group size, mother–infant interaction and infant social networks across all group-years. Individual variation in the degree to which infant social networks were kin biased was related both directly to the infant's social milieu and indirectly to its relationship with its mother. Given the long-term nature of the mother's influence on social networks, these results suggest that demographic influences on developmental processes can lead to progressive changes in social structure in the absence of resource scarcity.

Effects of short- and long-term withdrawal from gestational cocaine treatment on maternal behavior and aggression in Sprague-Dawley rats.

Pregnant rats were treated with 30 mg/kg per day cocaine or normal saline either throughout gestation (GD 1-20, cocaine and saline withdrawal) or throughout the gestation and continuing into lactation for 10 days postpartum (cocaine and saline nonwithdrawal). All cocaine-treated dams exhibited more disruptions in the onset of maternal behavior (retrieval, licking, crouching) and were more aggressive (threats and attacks) towards an intruder on postpartum day 6 than saline-treated dams. There were no significant differences in these behaviors between withdrawn and nonwithdrawn cocaine-treated dams. These findings indicate that changes in maternal behavior following chronic moderate cocaine treatment are not simply the result of withdrawal from cocaine treatment following gestation and that other possible mechanisms should be examined.