Behavior Of Pups Research Articles

Repeated cross-fostering affects maternal behavior and olfactory preferences in rat pups.

Disturbances in early mother-infant relationships are strongly associated with changes in the development of a number of physiological and behavioral systems in the neonate that can create a complex change in patterns of vulnerability throughout life. Institutionalized children, despite receiving adequate care, display important behavioral changes in adult life, and such changes are strongly associated with a lack of selective and consistent attachment to the maternal figure in early life. It is not yet clear how human adoption processes alter the mother-infant relationship early in life. Here, to mimic the situation of human adoption and explore the impact on the formation of attachment between the infant and a caregiver, we use a repeated cross-fostering (RCF) model in rodents in two postnatal periods, postnatal days (PND) 1 to 3 (early RCF) and 9 to 11 (late RCF). Early exposure but not late exposure to RCF reduces the pups' preference for the odor of the mother figure. Moreover, early exposure and slightly later exposure to RCF reduce maternal care and motivation in collecting the pups and bringing them to the nest. The RCF protocol creates an unstable environment for mother-pup interaction, but it seems to affect learned attachment to the mother only when it occurs during the corresponding sensitive period of development.

Using maternal rescue of pups in a cup to investigate mother-infant interactions in mice/rodents

Efficient parental care is indispensable for survival of the mammalian offspring, and therefore both parents and offspring cooperate to achieve the best performance. For example, when parents transport altricial offspring, the offspring immediately respond by reducing its cry and movement in both human infants and rodent pups. This coordinated set of central, motor and cardiac responses is designated as the Transport Response (TR) and is shown to facilitate maternal carrying in rodents. The present study aims to investigate the core behavioural characteristics of mother-infant interaction, and to investigate the mechanisms underlying the mother-pup cooperation using pharmacological and genetic manipulations (i.e. Oprm1-/). Along with the clear developmental changes of the pups' immobility and posture during maternal carrying as previously reported, there were also adaptations in maternal strategies, particularly in positioning of foothold and oral grasp over the pup's body, with the pups' age and pup's behaviour. Tree-based models elucidated that both of these maternal variables as well as percentage of pups' struggle predict the time required for pup retrieval from a cup. When the sensory-motor control in pups was disturbed by pharmacological or genetic manipulations, these core behaviours were inefficiently performed and impede maternal retrieval. Mother-infant mutual fit is a complex construct where several intermingled mechanisms are involved. Thus mothers and infants, when interacting, should be considered together as one whole system in which any change in one side or the other, affects the output of the whole dyad. The outcome of the interaction relays on a specific dynamic pattern of infant and maternal behaviours, which mutually change and adapt to fit each other's needs. Key features to reach a successful outcome of the interaction were the maternal retrieving strategy and infants’ Transport Response behaviour.

The Effects of Exercise on Pain and Reproductive Performance in Female Pregnant Mice With Neuropathic Pain.

Pain can have negative, physiological and psychological impacts on pregnancy. Pregnant women are fearful of using pain medication because of teratogenic effects. In this study, we evaluated whether exercise could lower pain sensitivity in pregnant mice with neuropathic pain and reduce the negative effects of maternal pain on newborns. We randomly assigned 32 female mice to one of four groups (eight mice/group): Sham surgery with standard environment (SE) or enriched environment (EE) or spare nerve injury (SNI) with SE or EE. Mice in EE groups had access to an exercise wheel. Mothers were evaluated for mechanical sensitivity with Von Frey filaments and for exercise performance with computerized running wheels. Mice were impregnated 2 weeks after the initiation of EE. Pups were weighed and measured for length at birth and evaluated for negative geotaxis, righting, forelimb grasping, rooting, and crawling at 3 days postpartum and for crawling at 6 days postpartum. Following euthanasia, mothers' frontal cortexes were analyzed for selected neuropeptides. After exercise exposure, only SNI-SE females remained neuropathic. Exercise levels were similar between EE groups. Some brain neuropeptides (endorphins, enkephalins, and oxytocin) from SNI females showed significant differences with exercise. Number of pups was significantly smaller in the SNI-SE group. Significantly more pups died at birth in the SNI-SE group, but pup behavior tests (except righting) were similar across groups. Exercise can reduce neuropathic pain in pregnant mice. Neuropathic pain does not impact motor neurodevelopment of mice pups but does appear to affect litter size and neonatal mortality.

Wnt signaling pathway is implicated in the alleviating effect of treadmill exercise on maternal separation-induced depression.

Maternal separation in the developmental stage has a negative influence on brain development and causes depression. The extracellular ligand, Wnt, and its receptors play an important role in axis formation and neural development. Exercise inhibits apoptosis, increases cell proliferation, and exerts antidepressive effect. In this study, the effect of treadmill exercise on the maternal separation-induced depression was investigated in the aspect of Wnt signaling pathway. The maternal separation started on the postnatal day 14. The rat pups in the exercise groups were forced to run on a treadmill for 30 min once a day from postnatal day 21 to postnatal day 34. The rat pups in the maternal separation and fluoxetine-treated group were intraperitoneally injected with 5-mg/kg fluoxetine once a day from postnatal day 21 to postnatal day 34. Forced swimming test was performed to evaluate the depression level. Western blotting was performed for the expressions of Wnt signaling ligands, Wnt2 and Wnt3a, and Wnt signaling inhibitors, Dkk1, and sFRP3. Maternal separation showed depressive behaviors in the forced swimming test. Treadmill exercise alleviated depressive behaviors in the maternal separation rat pups. Expressions of Wnt2 and Wnt3a were decreased by maternal separation. Treadmill exercise alleviated maternal separation-induced reduction of Wnt2 and Wnt3a expressions. Expressions of Dkk1 and sFRP3 in the hippocampus were increased by maternal separation. Treadmill exercise alleviated maternal separation-induced reduction of Dkk1 and sFRP3 expressions. Our study demonstrated that treadmill exercise activates Wnt signaling pathway, and then exerted antidepressive effect.

Maternal age influences offspring behaviour and growth efficiency during provisioning in northern elephant seals

Offspring growth rates impact fitness and can be influenced by maternal effects. Despite efforts to understand the influence of maternal traits (e.g. age, size, body condition) on reproductive effort, much less is known about how maternal traits and environment influence the behaviour of offspring and ultimately, how offspring behaviour may influence the efficiency of the translation of maternal investment into offspring growth. Offspring of capital breeders, such as the northern elephant seal, Mirounga angustirostris, are nursed exclusively from maternal body reserves and investment is limited by the resources acquired prior to parturition. Combined new and previously published milk energy intake and offspring storage data (N = 38) suggest impacts of maternal age on growth efficiency that are independent of rates of energy delivery. To determine the mechanisms underlying this effect of maternal age, behavioural data were collected from pups of 46 known-age females, from parturition to weaning, across 6 years and three different sites along the central California coast, representing 3954 seal-hours of observation. Pup behaviours were divided into five mutually exclusive categories that potentially impacted pup energetics. The offspring of older females spent more time resting, while offspring of younger females spent more time locomoting and distant from their mother. As pups developed, they spent more time suckling and locomoting and less time resting. Pup behaviour showed strong diel patterns, with activity decreasing over the day. The magnitude of these relationships varied between rookeries, suggesting influences of harem size, topography or environmental features on pup behaviour. Together these findings suggest direct impacts of maternal age and breeding experience on pup behaviour and growth efficiency.

Chemical Profiles of Integumentary and Glandular Substrates in Australian Sea Lion Pups (Neophoca cinerea).

Recognition of individuals or classes of individuals plays an important role in the communication systems of many mammals. The ability of otariid (i.e., fur seal and sea lion) females to locate and identify their offspring in colonies after returning from regular foraging trips is essential to successful pup rearing. It has been shown that olfaction is used to confirm the identity of the pup by the mother when they reunite, yet the processes by which this chemical recognition occurs remain unclear. Using gas chromatography-mass spectrometry, we examined chemical profiles of integumentary and glandular secretions/excretions from pre- and post-molt Australian sea lion pups (Neophoca cinerea) and compared fur and swab samples to assess data collection methods. Multivariate statistics were applied to assess differences in chemical composition between body regions and sexes. We found differences among secretions from various body regions, driven by the distinctiveness of the oral odor mixture. The fine-scale trends in pre- and post-molt pups seem to differ due to changes in the behavior of pups and consequent decrease in the transfer of compounds among adjacent body regions in older pups. Volatile compounds from exocrine substrates were not distinct for different sexes. We also show that swab samples provide better data for exploring social olfaction than fur samples for this species. Obtaining fundamental chemical information, in this case chemical profiles of animals, and discerning differences in chemical composition is an important step toward fully exploring the intricacies of mother-offspring olfactory recognition and its underlying processes.

Both maternal care received and genotype influence stress-related phenotype in female rats.

Rat dams differ naturally in the level of maternal care they provide to their offspring within the same litter. We explored possible mechanisms of differential maternal care focused on genetic variation. We examined single nucleotide polymorphisms in the glucocorticoid receptor, FK506-binding protein, and serotonin transporter genes in two separate cohorts, and the relationship between differential maternal care received, genotype, and offspring phenotype. Allelic variation in all three genes was significantly associated with levels of maternal care received by offspring and behavioral and endocrine stress responses in adulthood. Differences in pup behavior were also associated with allelic variation in these genes. Together, these results indicate that the dam/pup interaction is dynamic and implicate the genotype of the offspring in influencing the level of maternal care received. They further suggest that some genotypes may have a dampening effect on the impact of maternal care on stress-related phenotypes in adulthood.

Automatic classification of laparos call and playback tests at cuniculture nests

The vocal behavior of rabbit pups was monitored during their first 15 days of life. It was possible to estimate the average of vocalizations issued in the nest by correlation calculations applied to spectrographic images. We performed experimental tests of playback and observed the behavior between the offspring and the doe during the period of lactation. The vocalizations can be important in pup recognition and consequently, stimulate the doe to nurse their offspring, decreasing the rate of mortality in the breeding phase.

Term or Preterm Cesarean Section Delivery Does Not Lead to Long-term Detrimental Consequences in Mice.

Epidemiological studies have provided contradictory data on the deleterious sequels of cesarean section (C-section) delivery and their links with developmental brain disorders such as Autism Spectrum Disorders. To gain better insight on these issues, we have now compared physiological, morphological, and behavioral parameters in vaginal, term, and preterm C-section delivered mice. We report that C-section delivery does not lead to long-term behavioral alterations though preterm C-section delivery modifies communicative behaviors in pups. Moreover, C-section delivery neither alters the gamma-aminobutyric acid (GABA) developmental excitatory to inhibitory shift nor the frequency or amplitude of glutamatergic and GABAergic postsynaptic currents in hippocampal pyramidal neurons. However, these neurons present an underdeveloped dendritic arbor at birth in pups born by C-section delivery, but this difference disappears 1 day later suggesting an accelerated growth after birth. Therefore, C-section delivery, with prematurity as an aggravating factor, induces transient developmental delays but neither impacts the GABA developmental sequence nor leads to long-term consequences in mice. The deleterious sequels of C-section delivery described in epidemiological studies might be due to a perinatal insult that could be aggravated by C-section delivery.

Sink or swim: Early dive behavior in Weddell seal (Leptonychotes weddellii) pups

Weddell seals (Leptonychotes weddellii) are a model species for studying diving physiology. However, Weddell seal pups are not born with the elite diving capabilities of their adult counterparts and must develop their skills so they can survive into adulthood. Previous research has excluded an examination of pups' initial diving attempts. The aim of this study was to investigate the development of diving capabilities throughout ontogeny, beginning at 1 week of age, to create a more complete trajectory of development. To do this, we examined the dive behavior and blood oxygen stores of Weddell seal pups over the first seven weeks of life. Flipper‐mounted time‐depth recorders (Lotek LAT1800XLFP) were attached to 1‐week‐old Weddell seal pups (n=8) in Erebus Bay, Antarctica, and were recovered when the pups were 7 weeks of age. Time spent in the water, maximum dive depth, dive duration, bottom time, and post‐dive interval were calculated to characterize dive behavior. Blood samples were collected from three of these pups at 1 week, 3 weeks, 5 weeks, and 7 weeks of age. We measured hematocrit, hemoglobin, and red blood cell counts for all blood samples to assess age‐related changes in blood oxygen stores. Time spent in the water and number of dives per day both significantly increased as pups got older (P < 0.0001). The time pups spent in the water per day ranged between 1 min and 21 h. Although the maximum dive depths for pups ranged between 3 m and 14.78 m, the majority of “dives” were less than 2 m. Hematocrit, hemoglobin, and red blood cell counts also increased throughout early development. Correlations between dive behavior and hematology indicate dive behavior, rather than age, is a better predictor of oxygen storage development. Based on these data, we conclude early experience in the water is an important driver of physiological development in dependent Weddell seal pups. New swimmers may prioritize acclimatization to the water and strengthening their swimming muscles over attempting deeper foraging dives.Support or Funding InformationThis project was funded by a grant from the National Science Foundation (#1543539).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Chewing during prenatal stress prevents prenatal stress-induced suppression of neurogenesis, anxiety-like behavior and learning deficits in mouse offspring.

Prenatal stress (PS) induces learning deficits and anxiety-like behavior in mouse pups by increasing corticosterone levels in the dam. We examined the effects of maternal chewing during PS on arginine vasopressin (AVP) mRNA expression in the dams and on neurogenesis, brain-derived neurotrophic factor (BDNF) mRNA expression, learning deficits and anxiety-like behavior in the offspring. Mice were divided into control, stress and stress/chewing groups. Pregnant mice were exposed to restraint stress beginning on day 12 of pregnancy and continuing until delivery. Mice in the stress/chewing group were given a wooden stick to chew during restraint stress. PS significantly increased AVP mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus in the dams. PS also impaired learning ability, suppressed neurogenesis and BDNF mRNA expression in the hippocampus, and induced anxiety-like behavior in the offspring. Chewing during PS prevented the PS-induced increase in AVP mRNA expression of the PVN in the dams. Chewing during PS significantly attenuated the PS-induced learning deficits, anxiety-like behavior, and suppression of neurogenesis and BDNF mRNA expression in the hippocampus of the offspring. Chewing during PS prevented the increase in plasma corticosterone in the dam by inhibiting the hypothalamic-pituitary-adrenal axis activity, and attenuated the attenuated the PS-induced suppression of neurogenesis and BDNF expression in the hippocampus of the pups, thereby ameliorating the PS-induced learning deficits and anxiety-like behavior. Chewing during PS is an effective stress-coping method for the dam to prevent PS-induced deficits in learning ability and anxiety-like behavior in the offspring.

Early emergence of altered 5-HT2A receptor-evoked behavior, neural activation and gene expression following maternal separation

The early stress of Maternal Separation (MS) contributes to the establishment of adult psychopathology. The serotonergic (5-HT) system is implicated during this temporal window in mediating the development of mood-related behaviors. MS is reported to evoke altered 5-HT2A receptor function in adulthood. However, the ontogeny of altered 5-HT2A receptor responsivity following MS remains unknown. Here, we examined 5-HT2A receptor agonist, DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane) (2mg/kg) evoked responses, namely stereotypical head-twitch behaviors in control and MS Sprague-Dawley rat pups at postnatal day 21 (P21). MS involved a separation of pups from the dam for 3h daily from postnatal day 2–14. MS pups at P21 exhibited significantly enhanced head-twitch behaviors compared to controls. Using c-Fos cell counting we examined neural activation in control and MS pups following DOI treatment. MS pups exhibited altered DOI-evoked c-Fos expression within all mPFC subdivisions, but not in the hippocampus, lateral septum and hypothalamus, suggesting differential prefrontal neural activation upon 5-HT2A receptor stimulation following early stress. Gene profiling of 5-HT2A receptor-regulated immediate early genes (IEGs) indicated a decline in the expression of Fos, Fra1 and Egr1 mRNA under baseline conditions in the mPFC of MS pups. MS pups also showed an altered pattern in the regulation of several 5-HT2A receptor-regulated IEGs (Fos, Fra1, Bdnf, Egr1, Egr3) following DOI treatment. Collectively, these results highlight an early emergence of altered 5-HT2A receptor-evoked behavioral responses and neural activation patterns in multiple brain regions in animals with a history of MS.

Forced but not free-choice nicotine during lactation alters maternal behavior and noradrenergic system of pups: Impact on social behavior of adolescent isolated male rats

Adverse effects of nicotine during pregnancy have been greatly studied, while nowadays few works are focused on consequences of maternal tobacco smoking after birth. The present study investigated the behavioral and early neurochemical effects of nicotine treatment during first weeks of post-natal life in rats. We used “free choice” treatment (H2O+NIC dams could drink from two bottles, containing 10mg/L nicotine hydrogen tartrate salt, or water) versus “forced choice” (NIC+NIC mothers could drink from two bottles both containing nicotine hydrogen tartrate salt, range from 0.75mg/L to 4.09mg/L). We found that only “forced nicotine” had impact on maternal behavior, causing increased high-quality maternal care. This immediately impacted on neuro-chemical development, affecting NE levels (only males) in pup’s striatum and prefrontal cortex (pFC) at PND 12. After weaning, animals were reared in normal conditions (two brother rats) or in Social Isolation. After two weeks, they were tested with Social Interaction Test (isolated rats met non-isolated opponents, siblings vs. non-siblings). As expected, isolated rats displayed an aggressive form of soliciting behavior: when facing an isolated unknown partner, the non-isolated rat tried to escape. Interestingly, if their dams were exposed to forced nicotine, both rats sooner behaved very affiliative (possibly empathic) between non-sibling partners. As expected, being exposed to post-natal nicotine could alter neuro-chemical development, but with important interactions between both maternal care and adolescent social behavior.

Oxytocin receptor antagonist treatments alter levels of attachment to mothers and central dopamine activity in pre-weaning mandarin vole pups

Oxytocin (OT) is known to be important in mother-infant bonding. Although the relationship between OT and filial attachment behavior has been studied in a few mammalian species, the effects on infant social behavior have received little attention in monogamous species. The present study examined the effects of OT receptor antagonist (OTA) treatment on attachment behavior and central dopamine (DA) activity in male and female pre-weaning mandarin voles (Microtus mandarinus). Our data showed that OTA treatments decreased the attachment behavior of pups to mothers, measured using preference tests at postnatal day 14, 16, 18 and 20. OTA treatments reduced serum OT concentration in pre-weaning pups and decreased tyrosine hydroxylase (TH) levels in the ventral tegmental area (VTA), indicating a decrease in central DA activity. In male and female pups, OTA reduced DA levels, DA 1-type receptor (D1R) and DA 2-type receptor (D2R) protein expression in the nucleus accumbens (NAcc). Our results indicate that OTA treatment inhibits the attachment of pre-weaning pups to mothers. This inhibition is possibly associated with central DA activity and levels of two types of dopamine receptor in the NAcc.

Омега-3 полиненасыщенные жирные кислоты при введении кормящим крысам модулируют поведение крысят, перенесших стрессирование путем многократного введения физиологического раствора в неонатальном периоде

Омега-3 полиненасыщенные жирные кислоты (ПНЖК) могут оказывать антидепрессивное, анксиолитическое и антистрессорное действие, однако данные противоречивы. Недавно на модели тревожно-депрессивного состояния, индуцированного неонатальным действием ингибитора дипептидилпептидазы IV дипротина А, мы показали, что омега-3 ПНЖК наряду с антидепрессивным действием также повышают тревожность у крысят опытной группы и нарушают эмоциональное поведение контрольных животных, подвергнутых многократному введению физиологического раствора (ФР). Цель работы - изучение влияния омега-3 ПНЖК при их введении кормящим крысам Вистар, на эмоционально-мотивационное поведение крысят, подвергнутых стрессогенной процедуре многократного введения ФР на 2-й - 3-й неделях постнатального развития, и интактных животных в динамике взросления. Методика. Омега-3 ПНЖК вводили крысам в период лактации перорально в дозе 0,3 г/кг в течение 28 дней. ФР вводили внутрибрюшинно в период с 5-го по 18-й дни постнатального развития. Эмоционально-мотивационное поведение крыс оценивали с помощью общепринятых методов. Результаты. Омега-3 ПНЖК предотвращали появление признаков депрессивноподобного поведения и оказывали психостимулирующее действие на животных, перенесших стрессирование в раннем неонатальном периоде. Омега-3 ПНЖК также нормализовали вызванные стрессом нарушения социального взаимодействия неагрессивного характера у крыс подросткового возраста и взрослых животных, однако способствовали повышению агрессивности у взрослых интактных крыс. Независимо от факта стрессирования, омега-3 ПНЖК по разным показателям тревожности оказывали как анксиолитическое, так и анксиогенное действие на крыс-подростков, тогда как у взрослых животных обнаружено только их анксиогенное влияние. У стрессированных и интактных взрослых крыс омега-3 ПНЖК вызывали снижение ориентировочно-исследовательской активности. Заключение. Омега-3 ПНЖК в условиях их приема кормящими самками, оказывают как позитивное, так и негативное влияние на эмоционально-мотивационное поведение потомства, перенесшего в неонатальном периоде стрессирование путем многократного введения ФР. Эффекты омега-3 ПНЖК различаются у животных подросткового и взрослого возраста. Угнетающее действие на психомоторную активность и анксиогенное влияние омега-3 ПНЖК проявляется как у стрессированных, так и у интактных крыс, что следует учитывать при разработке подходов к терапии психоневрологических расстройств с использованием омега-3 ПНЖК.Omega-3 polyunsaturated fatty acids (PUFAs) may exert antidepressant, anxiolytic and anti-stress effects, but the data are contradictory. Recently, using the model of experimental anxiety-depressive disorder caused by the neonatal action of an inhibitor of dipeptidyl peptidase IV diprotin A, we have shown that omega-3 PUFAs along with an antidepressant effect also increase anxiety in the rat pups in the experimental group and disrupt emotional behavior in control animals subjected to repeated administration of saline. The purpose of this work was to study the effects of omega-3 PUFAs when administered to the lactating Wistar rats, on the emotional and motivational behavior of the rat pups exposed to the procedure of the repeated saline administration on second - third weeks of postnatal development and intact rats in the dynamics of growing up. Methods. Omega-3 PUFAs were administered to lactating rats at a dose 0.3 g/kg, per os, for 28 days. Saline was administered intraperitoneally on postnatal days 5-18. We assessed emotional and motivational behavior using conventional methods. Results. Omega-3 PUFAs prevented the appearance of the symptoms of depressive-like behavior and exerted a psycho stimulative effect on the animals that underwent stress in the early neonatal period. Omega-3 PUFAs also normalized stress-related impairment of social non-aggressive interaction in adolescent and adult rats but promoted increased aggression in adult intact rats. Regardless of whether the stress, omega-3 PUFAs exhibited both anxiolytic and anxiogenic effects for different anxiety indicators in adolescent rats, whereas in adult animals only anxiogenic effect was detected. In adult stressed and intact rats, omega-3 PUFAs caused a decrease in exploratory activity. Conclusion. Omega-3 PUFAs when administered to the lactating females, exert both positive and negative effects on the emotional and motivational behavior of the offspring, which underwent stress by repeated saline administration in the neonatal period. Omega-3 PUFAs action differs in adolescent and adult rats. The inhibitory effect on psychomotor activity and anxiogenic effects of omega-3 PUFAs appear in both stressed and intact rats that should be taken into account when developing approaches to the treatment of psycho-neurological disorders using omega-3 PUFAs.

Chronic postnatal monoamine oxidase inhibition affects affiliative behavior in rat pups

Monoamine neurotransmitters serotonin (5-HT), dopamine (DA), and noradrenaline (NA) act as important modulators of mammalian brain development and represent neurobiological substrates of affiliative behavior reflected in rat pups as a tendency to huddle or produce ultrasonic vocalizations (USV) when separated from the nest. Monoamines are metabolized through oxidative deamination catalyzed by the mitochondrial enzyme monoamine oxidase (MAO). In this study, we examined the consequences of postnatal MAO inhibition on affiliative behavior in rat pups. Pups received daily injections of either an irreversible non-selective MAO inhibitor tranylcypromine (TCP) or saline, from post-natal day (PND) 1 to PND 22. Quantitative and qualitative components of USV were analyzed on PNDs 10, 13 and 16 in order to determine the level of separation-induced anxiety and the modality of vocal communication. In comparison to control pups, TCP-treated pups displayed higher cortical 5-HT, DA and NA levels, higher peripheral 5-HT concentration, lower body mass throughout the pre-weaning period, higher isolation-induced drop in body temperature, and reduced total number of calls. Furthermore, they produced lower pitched calls of longer average duration without a preferable waveform. Our results demonstrate that chronic MAO inhibition by TCP primarily affects 5-HT concentrations, but also raises central catecholamine levels. They further indicate that disturbed monoaminergic homeostasis during early postnatal development leads to decreased weight-gain, compromised thermoregulation, and altered affiliative behavior in pre-weaning pups as reflected in reduced separation anxiety and inadequate vocal communication. Finally, they suggest a need for thorough examination of the potential effects of TCP and other monoamine inhibitors on the developing human brain.

Fibroblast growth factor 2 alters the oxytocin receptor in a developmental model of anxiety-like behavior in male rat pups

We aimed to determine the short-term effects of early-life stress in the form of maternal separation (MS) on anxiety-like behavior in male rat pups. In order to assess anxiety, we measured 40kHz separation-induced ultrasonic vocalizations (USV) on postnatal day (PND) 11. We further aimed to evaluate the potential involvement of two neurochemical systems known to regulate social and anxiety-like behaviors throughout life: oxytocin (OT) and fibroblast growth factor 2 (FGF2). For these purposes, we tested the effects of neonatal administration (on PND1) of an acute dose of FGF2 on USV and its potential interaction with MS. In addition, we validated the anxiolytic effects of OT and measured oxytocin receptor (OTR) gene expression, binding and epigenetic regulation via histone acetylation. Our results show that MS potentiated USV while acute administration of OT and FGF2 attenuated them. Further, we found that both FGF2 and MS increased OTR gene expression and the association of acH3K14 with the OTR promoter in the bed nucleus of the stria terminalis (BNST). Comparable changes, though not as pronounced, were also found for the central amygdala (CeA). Our findings suggest that FGF2 may exert its anxiolytic effects in male MS rats by a compensatory increase in the acetylation of the OTR promoter to overcome reduced OT levels in the BNST.

Metabolic activation of amygdala, lateral septum and accumbens circuits during food anticipatory behavior

When food is restricted to a brief fixed period every day, animals show an increase in temperature, corticosterone concentration and locomotor activity for 2–3h before feeding time, termed food anticipatory activity. Mechanisms and neuroanatomical circuits responsible for food anticipatory activity remain unclear, and may involve both oscillators and networks related to temporal conditioning. Rabbit pups are nursed once-a-day so they represent a natural model of circadian food anticipatory activity. Food anticipatory behavior in pups may be associated with neural circuits that temporally anticipate feeding, while the nursing event may produce consummatory effects. Therefore, we used New Zealand white rabbit pups entrained to circadian feeding to investigate the hypothesis that structures related to reward expectation and conditioned emotional responses would show a metabolic rhythm anticipatory of the nursing event, different from that shown by structures related to reward delivery. Quantitative cytochrome oxidase histochemistry was used to measure regional brain metabolic activity at eight different times during the day. We found that neural metabolism peaked before nursing, during food anticipatory behavior, in nuclei of the extended amygdala (basolateral, medial and central nuclei, bed nucleus of the stria terminalis), lateral septum and accumbens core. After pups were fed, however, maximal metabolic activity was expressed in the accumbens shell, caudate, putamen and cortical amygdala. Neural and behavioral activation persisted when animals were fasted by two cycles, at the time of expected nursing. These findings suggest that metabolic activation of amygdala-septal-accumbens circuits involved in temporal conditioning may contribute to food anticipatory activity.

Effects of environmental variables on surface temperature of breeding adult female northern elephant seals, Mirounga angustirostris, and pups

Pinnipeds spend extended periods of time on shore during breeding, and some temperate species retreat to the water if exposed to high ambient temperatures. However, female northern elephant seals (Mirounga angustirostris) with pups generally avoid the water, presumably to minimize risks to pups or male harassment. Little is known about how ambient temperature affects thermoregulation of well insulated females while on shore. We used a thermographic camera to measure surface temperature (Ts) of 100 adult female elephant seals and their pups during the breeding season at Point Reyes National Seashore, yielding 782 thermograms. Environmental variables were measured by an onsite weather station. Environmental variables, especially solar radiation and ambient temperature, were the main determinants of mean and maximum Ts of both females and pups. An average of 16% of the visible surface of both females and pups was used as thermal windows to facilitate heat loss and, for pups, this area increased with solar radiation. Thermal window area of females increased with mean Ts until approximately 26°C and then declined. The Ts of both age classes were warmer than ambient temperature and had a large thermal gradient with the environment (female mean 11.2±0.2°C; pup mean 14.2±0.2°C). This large gradient suggests that circulatory adjustments to bypass blubber layers were sufficient to allow seals to dissipate heat under most environmental conditions. We observed the previously undescribed behavior of females and pups in the water and determined that solar radiation affected this behavior. This may have been possible due to the calm waters at the study site, which reduced the risk of neonates drowning. These results may predict important breeding habitat features for elephant seals as solar radiation and ambient temperatures change in response to changing climate.

Sex-dependent role of vesicular glutamate transporter 3 in stress-regulation and related anxiety phenotype during the early postnatal period

Stress and related disorders are in the focus of interest and glutamate is one of the most important neurotransmitters that can affect these processes. Glutamatergic neurons are characterized by vesicular glutamate transporters (VGluT1-3) among which vGluT3 is unique contributing to the non-canonical, neuromodulatory effect of glutamate. We aimed to study the role of vGluT3 in stress axis regulation and related anxiety during the early postnatal period using knockout (KO) mice with special focus on sex differences. Anxiety was explored on postnatal day (PND) 7-8 by maternal separation-induced ultrasonic vocalization (USV). Stress-hormone levels were detected 60 min after intraperitoneal lipopolysaccharide (LPS) injection 7 days later. Both genotypes gained weight, but on PND 14-15 KO mice pups had smaller body weight compared to wild type (WT). vGluT3 KO mice reacted to an immune stressor with enhanced adrenocorticotropin (ACTH) and corticosterone secretion compared to WT. Although there was a tendency for enhanced anxiety measured by more emitted USV, this did not reach the level of significance. The only sex-related effect was the enhanced corticosterone reactivity in male pups. For the HPA axis regulation in neonates vGluT3 expression seems to be dispensable under basal conditions, but is required for optimal response to immune stressors, most probably through an interaction with other neurotransmitters. Disturbance of the fine balance between these systems may result in a borderline enhanced anxiety-like behavior in vGluT3 KO pups.