Behavior In Rat Pups Research Articles

The influence of maternal separation on the development of voiding and behavior in rat pups

Aim:This study aimed to investigate the effects of early-life stress resulting from maternal separation (MS) on urinary function and behavioral changes. Methods:We categorized 85 rat pups into control and MS groups. Two groups of each sex during post-weaning (3 weeks old) and maturity (9 weeks old) were compared. Urinary function was evaluated using metabolic cages and continuous cystometry. Morphological changes were assessed based on bladder weight and staining. In behavioral experiments, spatial working memory using the Y-maze and anxiety-like behavior in the elevated plus-maze were assessed. Results:In the metabolic cage test, the single voiding volume decreased in the 3-week-old male and female MS groups. In continuous cystometry, the intercontraction interval was shortened in the 9-week-old male and female MS groups. MS showed a significant change in bladder weight and wall thickness in 3-week-old females. Conversely, a change in bladder wall thickening was observed in male rats aged 9 weeks. In the Y-maze, no differences were found in alternation. In the elevated plus-maze test, the 3-week-old MS groups of both sexes had fewer entries into the open arm and slower mean velocities, while the 9-week-old groups had a greater number of entries into the open arm and a faster average speed. Conclusion:MS affects voiding behavior and bladder activity during the early phase of maturation. After growth, bladder overactivity and less anxiety-like hyperactivity co-exist, suggesting that early-life stress due to MS may have lasting effects on common neural circuits related to urinary function and behavior.

The Behavior and Postnatal Development in Infant and Juvenile Rats After Ultrasound-Induced Chronic Prenatal Stress.

Fetal development is susceptible to environmental factors. One such factor is exposure to stress during pregnancy. The present study aimed to investigate the effects of chronic prenatal stress (PS) on the development and behavior of rat offspring during infancy and juvenile ages. Existing approaches to modeling prenatal stress on animals do not correlate with the main type of stress in pregnant women, namely psychological stress. We used a new stress paradigm in the experiment, namely, stress induced by exposure to variable frequency ultrasound (US), which acted on pregnant Wistar rats on gestational days 1–21. This type of stress in rodents can be comparable to psychological stress in humans. We assessed physical development, reflex maturation, motor ability development, anxious behavior, response to social novelty, and social play behavior in male and female offspring. Additionally, we investigated maternal behavior and the effect of neonatal handling (NH) on behavior. Prenatal stress did not affect postnatal developmental characteristics in rat pups, but prenatally stressed rats had higher body weight in early and adult age than controls. Prenatal exposure to a stressor increased anxiety in the open-field test (OF), changed social preferences in the social novelty test (SN), and impaired social play behavior in males. Neonatal handling reduced anxiety and restored social behavior, but evoked hyperactive behavior in rat pups. Maternal behavior did not change. Our study demonstrated for the first time that exposure to variable frequency ultrasound during pregnancy influences offspring development and impairs behavior, correlating with the effects of other types of stress during pregnancy in rodents. This supports the idea of using this exposure to model prenatal stress.

The role of Hipk2-p53 pathways in arsenic-induced autistic behaviors: A translational study from rats to humans

Previous studies have associated the risk of autism spectrum disorder (ASD) with increased exposures to metals and metalloids such as arsenic. In this study, we used an animal-to-human translational strategy to identify key molecular changes that potentially mediated the effects of arsenic exposures on ASD development. In a previously established rat model, we have induced autistic behaviors in rat pups with gestational arsenic exposures (10 and 45 μg/L As2O3 in drinking water). Neuronal apoptosis and the associated epigenetic dysregulations in frontal cortex were assayed to screen potential mediating pathways, which were subsequently validated with qPCR, western blotting, and immunohistochemistry analyses. Furthermore, the identified pathway, along with serum levels of 26 elements including arsenic, were characterized in a case-control study with 21 ASD children and 21 age-matched healthy controls. In animals, we found that arsenic exposures caused difficulties of social interaction and increased stereotypic behaviors in a dose-dependent manner, accompanied by increased neuronal apoptosis and upregulation of Hipk2-p53 pathway in the frontal cortex. In humans, we found that serum levels of Hipk2 and p53 were 24.7 (95%CI: 8.5 to 43.4) % and 23.7 (95%CI: 10.5 to 38.5) % higher in ASD children than in healthy controls. ASD children had significantly higher serum levels of 15 elements, among which arsenic, silicon, strontium, and vanadium were positively associated with both Hipk2 and p53. Results from both the rat arsenic exposure and human case-control studies suggest a likely role of Hipk2-p53 pathway in ASD development induced by exposures to environmental pollutants such as arsenic.

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.

Maternal behavior influences development of a reflexive action pattern in the newborn rat.

This study examined the effect of maternal behavior on the expression and postnatal development of a reflexive behavior in rat pups. In neonatal rats, the leg extension response (LER) is a bilateral hyperextension of the hindlimbs in response to maternal anogenital licking (AGL). Past research has found that intranasal application of zinc sulfate (ZnSO4 ) to the dam induces hyponosmia, thereby reducing the incidence of AGL. In this study, pregnant dams received intranasal application of air (control), distilled water (control), or ZnSO4 on the day before birth and every other day thereafter until postnatal day 9 (P9). The LER was experimentally evoked in pups, using a vibrotactile device, at P1, P5, or P10. Pups born to ZnSO4 -treated dams showed significantly shorter bilateral LER durations and significantly smaller ankle angles than pups born to control dams. Reduction of overall maternal AGL approached significance, and afternoon AGL was significantly reduced. These data suggest that maternal behavior influenced development of the LER in rat pups, demonstrating the influence of maternal care on behavioral development during the perinatal period.

Effects of 6 Weeks Exposure of 3.5 mT (ELF EMF) on Some Animal behaviors in White Albino Rat (Sprague Dawley) Pups

The EMF nowadays is considered as a big source of harmful effects on our life on earth. So, the aim of this experimental study was to investigate the effect of extremely low frequency electromagnetic fields (ELF EMF) on some animal behaviors in rat pups. Laboratory animals with three different ages 2, 4, and 6 weeks were used as control and exposed groups, were placed in a Helmholtz coil electromagnetic field apparatus created for 1 hour and exposure to a 3.5mT, 50Hz. The results showed that exposure of a 50 Hz, 3.5mT electromagnetic field for 1h, has fluctuated effects on some animal behaviors like (activity, inactivity, motion, response to sound, and light, eating, and redness of limbs) in rat pups.

The effects of prenatal exposure to a 900 megahertz electromagnetic field on hippocampus morphology and learning behavior in rat pups

This study was planned to examine the effect on hippocampus morphology and learning behavior in rat pups exposed to a 900 megahertz (MHz) electromagnetic field (EMF) in the prenatal period. Sprague Dawley rats weighing 180-250 g at the beginning of the study and with a regular cycle were left to mate with male rats. The following day, rats identified as pregnant using the vaginal smear test were divided into two groups; control (n=3) and EMF (n=3). No procedure was performed in the control group. The EMF group was exposed to 900 MHz EMF for 1h per day on days 13 to 21 of pregnancy. Female rat pups were removed from their mothers at 21 days old. Two newborn rat groups were then established, a 13 member control group and a 10 member EMF group. We foresaw that maternal separation anxiety might develop in the rat pups, and behavioral tests commenced 4 days later. Radial arm maze and passive avoidance tests measuring learning and memory performance and the open field test to evaluate locomotor activities were applied. All rats were decapitated on the 32nd day of the study and brain tissues removed. These were fixed in paraffin and underwent routine histological tissue analyses. Sections were taken, stained with Cresyl fast violet and subjected to histopathological examination. Positive effects on learning behavior were determined in the EMF group rats in the radial arm maze (p=0.007) and passive avoidance (p=0.037) tests, administered to both groups under identical conditions, while no statistically significant difference was determined in the open field test (p=0.05) results. The absence of any statistical difference in the open field test shows that the animals were not exposed to any stress during application of the test. No pathology was determined in the control group at histopathological examination of the sections. In contrast, neuronal and morphological compromise was observed in the EMF group. Our results show that exposure to a 900 MHz EMF in the prenatal period had an adverse effect on female pups learning behavior and also caused histopathological changes in the hippocampus.

The Effects of Prenatal Exposure to a 900 Megahertz Electromagnetic Field on Hippocampus Morphology and Learning Behavior in Rat Pups

The purpose of this study was to examine the effect on hippocampus morphology and learning behavior in rat pups following prenatal exposure to a 900 megahertz (MHz) electromagnetic field (EMF). Female Sprague Dawley rats weighing 180-250 g were left to mate with males. The following day, pregnant rats identified as such by the vaginal smear test were divided into two groups, control (n=3) and EMF (n=3). No procedures were performed on the control group. The rats in the EMF group were exposed to 900 MHz EMF on days 13 to 21 of pregnancy, for 1 h a day. Female rat pups were removed from their mothers at 22 days old. We then established two newborn rat groups, a 13 member control group and a 10 member EMF group. Radial arm maze and passive avoidance tests were used to measure rat pups’ learning and memory performance. All rats were decapitated on the postnatal 32nd day. Routine histological procedures were performed on the brain tissues, and sections were stained with Cresyl fast violet. The radial arm maze (p=0.007) and passive avoidance (p=0.032) tests were administered to both groups under identical conditions, and compromised learning behavior was determined in the EMF group rats. Morphological compromise was also determined in the EMF group sections. Our results show that the application of a 900 MHz EMF in the prenatal period adversely affected female pups’ learning behavior and also resulted in histopathological changes appearing in the hippocampus. NeuroQuantology | December 2013 | Volume 11 | Issue 4 | Page 582-590

Maternal Thimerosal Exposure Results in Aberrant Cerebellar Oxidative Stress, Thyroid Hormone Metabolism, and Motor Behavior in Rat Pups; Sex- and Strain-Dependent Effects

Methylmercury (Met-Hg) and ethylmercury (Et-Hg) are powerful toxicants with a range of harmful neurological effects in humans and animals. While Met-Hg is a recognized trigger of oxidative stress and an endocrine disruptor impacting neurodevelopment, the developmental neurotoxicity of Et-Hg, a metabolite of thimerosal (TM), has not been explored. We hypothesized that TM exposure during the perinatal period impairs central nervous system development, and specifically the cerebellum, by the mechanism involving oxidative stress. To test this, spontaneously hypertensive rats (SHR) or Sprague-Dawley (SD) rat dams were exposed to TM (200μg/kg body weight) during pregnancy (G10-G15) and lactation (P5-P10). Male and female neonates were evaluated for auditory and motor function; cerebella were analyzed for oxidative stress and thyroid metabolism. TM exposure resulted in a delayed startle response in SD neonates and decreased motor learning in SHR male (22.6%), in SD male (29.8%), and in SD female (55.0%) neonates. TM exposure also resulted in a significant increase in cerebellar levels of the oxidative stress marker 3-nitrotyrosine in SHR female (35.1%) and SD male (14.0%) neonates. The activity of cerebellar type 2 deiodinase, responsible for local intra-brain conversion of thyroxine to the active hormone, 3',3,5-triiodothyronine (T3), was significantly decreased in TM-exposed SHR male (60.9%) pups. This coincided with an increased (47.0%) expression of a gene negatively regulated by T3, Odf4 suggesting local intracerebellar T3 deficiency. Our data thus demonstrate a negative neurodevelopmental impact of perinatal TM exposure which appears to be both strain- and sex-dependent.

Ontogenetic Development of Dopaminergic Regulation of Grooming Behavior in Rats

The effect of the developing nucleus accumbens and ventrolateral striatum on grooming behavior in rat pups (1st month of life) and adult rats (2-12 months of life) was studied during activation of D1 and D2 dopamine receptors with apomorphine. Over the 1st week of life, apomorphine treatment was followed by hypersensitivity of D1 receptors in the nucleus accumbens. It was manifested in the early appearance of scratching and washing movements during ontogeny. The effect of activation was reduced after neonatal gangliosympathectomy. D2 receptors in the nucleus accumbens are identified on day 22 of life. D2 receptors in the ventrolateral striatum become functionally active during this period. Under these conditions, apomorphine increased significantly the duration of licking and biting movements. The number of D2 receptors in the ventrolateral striatum increases sharply during sexual maturity (2nd month of life). These changes are accompanied by an increase in the duration of oral stereotyped behavior. The duration of grooming movements was significantly reduced by the end of stereotyped behavior. The effect of apomorphine was most pronounced in 9-month-old animals. We conclude that the immature ventrolateral striatum has a reciprocal stimulatory effect on licking and biting movements during ontogeny. By contrast, the mature striatum produces a subordinate reciprocal inhibitory influence on various types of grooming movements.

Home seeking behavior in rat pups: Attachment vs. kin selection, oxytocin vs. vasopressin

We are interested in the rat as an animal model for infant–mother attachment. In the first experiment we tried to distinguish between a preference for familiar animals (attachment theory) and a preference for genetically related animals (kin selection theory) with the use of an early cross-fostering procedure. Genetic relationships did not influence preferences in cross-fostered pups on postnatal day17, only familiarity did. Subsequently we investigated if peptides known to influence affiliative behaviors were also effective in the present paradigm. Injection of oxytocin into the cisterna magna did not yield significant effects on preference, while vasopressin and desglycinamide-[Arg8]vasopressin reduced the preference in a dose dependent manner. The effect of vasopressin was completely blocked by pretreatment with the vasopressin V 1A receptor antagonist d(CH 2) 5Tyr(Me) 2,Arg 8-vasopressin. We discuss the explanatory power of attachment theory and kin selection theory with regard to preference experiments in rats and the usefulness of the rat as an animal model for infant–mother attachment.

Neonatal handling and the maternal odor preference in rat pups: Involvement of monoamines and cyclic AMP response element-binding protein pathway in the olfactory bulb

Early-life environmental events, such as the handling procedure, can induce long-lasting alterations upon several behavioral and neuroendocrine systems. However, the changes within the pups that could be causally related to the effects in adulthood are still poorly understood. In the present study, we analyzed the effects of neonatal handling on behavioral (maternal odor preference) and biochemical (cyclic AMP response element-binding protein (CREB) phosphorylation, noradrenaline (NA), and serotonin (5-HT) levels in the olfactory bulb (OB)) parameters in 7-day-old male and female rat pups. Repeated handling (RH) abolished preference for the maternal odor in female pups compared with nonhandled (NH) and the single-handled (SH) ones, while in RH males the preference was not different than NH and SH groups. In both male and female pups, RH decreased NA activity in the OB, but 5-HT activity increased only in males. Since preference for the maternal odor involves the synergic action of NA and 5-HT in the OB, the maintenance of the behavior in RH males could be related to the increased 5-HT activity, in spite of reduction in the NA activity in the OB. RH did not alter CREB phosphorylation in the OB of both male and females compared with NH pups. The repeated handling procedure can affect the behavior of rat pups in response to the maternal odor and biochemical parameters related to the olfactory learning mechanism. Sex differences were already detected in 7-day-old pups. Although the responsiveness of the hypothalamic–pituitary–adrenal axis to stressors is reduced in the neonatal period, environmental interventions may impact behavioral and biochemical mechanisms relevant to the animal at that early age.

Effect of perinatal iron deficiency on myelination and associated behaviors in rat pups

Iron deficiency in early development has been associated with irreversible alterations in brain myelination, but whether these neural changes are mirrored in altered behaviors in rats is not known. The goals were to determine if dietary induced gestational and lactational iron deficiency alters brain myelination and behaviors dependent on that system. Pregnant rats were randomly assigned to control (CN) or iron-deficient (ID) groups by providing iron-sufficient (40 ppm Fe) or iron-deficient (2–6 ppm Fe) diets from gestational day 5 through to weaning of pups. Thereafter, all offspring were fed the iron-sufficient diet. The myelination of subcortical white matter and the fimbria of hippocampus was measured by 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNPase, marker of oligodendrocyte) density at 25 days of age. Specific behavioral assessments were performed at multiple time points after birth. By contrast, ID rats had significantly lower density of CNPase in the subcortical white matter but the density of CNPase in fimbria of hippocampus was comparable to CN rats. Moreover, ID rats showed significant behavioral impairments in surface righting reflex, negative geotaxis reflex, vibrissae-evoked forelimb placing test and novel object recognition task. In conclusion, perinatal iron deficiency can significantly alter behavioral outcomes which may be due to delayed myelination in specific brain regions.

Huddling by rat pups: Ontogeny of individual and group behavior

A full account of behavioral development in rats must include the ontogeny of both individual and group behavior. Most of our accumulated knowledge, however, pertains to individual ontogenesis. Group behavior and its development are readily seen in the huddling behavior of rat pups. A rat huddle is an entity with characteristics and capabilities distinct from those of the individuals that comprise it. The huddle is a natural context for acquiring olfactory preferences for species odors. Olfactory learning in a huddle involves thermal and tactile stimulation from the mother's body but, surprisingly, not the rewards of suckling or of milk transfer. Although there is complete developmental continuity of huddling behavior, the sensory controls of huddling change dramatically during the first 2 weeks of postnatal life. Huddling behavior is initially controlled by thermal cues ("physiological huddling") and then becomes dominated by olfactory stimuli ("filial huddling"). The complex group behavior of huddling was modeled successfully with computational methods. Group behavior emerges from individual interactions, guided entirely by rules of individual behavior (no rules for group behavior). Three simple rules of autonomous activity/inactivity can spawn the patterns of aggregon formation displayed by groups of 7-day-old pups, but not by 10-day-olds. The developmental change evident by Day 10 requires adding a rule by which each individual is affected by the activity state of adjacent pups. Group behavior responded to manipulations of central oxytocin on Day 10, but not on Day 7.

Menhaden fish oil improves spatial memory in rat pups following recurrent pentylenetetrazole-induced seizures

This study investigated the effects of two supplementary dietary oils (fish oil and corn oil) as parts of isocaloric/isoproteic diets on growth, brain fatty acid composition, and behavior in rat pups with recurrent seizures. Recurrent seizures were induced by injecting rat pups with pentylenetetrazole (PTZ) between P10 (10 days of age) and P14. Either menhaden fish oil (FO) or corn oil (CO) was given as supplemental dietary oil throughout the experiment from P3 to P40. We assessed the effects of the two supplemental dietary oils on spatial memory, histomorphology, and fatty acid composition of brain tissue at the end of the study on P40. Rats that received dietary FO performed significantly better in the Morris water maze, a test used to examine spatial performance in rats; the FO group had significantly shorter escape latencies ( P = 0.041) during the escape test. Compared with the CO group, the FO group stayed a longer time ( P = 0.015) and swam a longer distance ( P = 0.033) in the target quadrant in the spatial probe test. The FO group had significantly higher brain docosahexaenoic acid ( P ⩽ 0.01) and significantly lower brain C20:3 n-6 and C20:4 n-6 ( P < 0.01 and P = 0.031) levels compared with the CO group, but the two groups did not differ significantly with respect to neuronal cell loss in the histomorphology study. This study demonstrated that, compared with CO, FO is better in improving spatial memory in rats following recurrent PTZ-induced seizures.

Pre‐anesthetic presence of an injured dam influences pups' locomotor behavior during emergence from anesthesia in rats

Pre-anesthetic mother-infant interaction is an important factor for smooth emergence of pediatric anesthesia. In many mammalian species, disruptions of the mother-infant relationship cause psychological and behavioral changes. This study was to investigate whether or not pre-anesthetic presence of an injured dam has an impact on locomotor behavior of rat pups. We used a video-tracking system to test the effects of pre-anesthetic relations between pups and their dams on pups' locomotor behavior during emergence from general anesthesia, in 40 3-week-old Sprague-Dawley male rats. Pups were divided into two groups: pups housed with a dam (n = 20) and those housed with an injured dam (n = 20). Pups were anesthetized with 1.2% halothane for 30 min. At emergence, we recorded their locomotor behavior for 15 min. Pre-anesthetic manipulation to dams significantly increased the distance traveled by pups. However, the manipulation did not cause any difference in the maximum velocity. Pre-anesthetic presence of an injured dam influenced pups' locomotor behavior at emergence from anesthesia.

A Biorobotic Investigation of Norway Rat Pups (Rattus norvegicus) in an Arena

Biorobotics research typically focuses on simulating specific aspects of animal biomechanics, sensory systems, and computational abilities. We have developed a novel methodology for integrating the study of biorobotics and animal behavior. We describe several metrics for characterizing and comparing rat pup and robot behavior without presupposing behavioral goal states. In the rat pup and robot experiments, we found that when 10-day-old Norway rats ( Rattus Norvegicus) are placed in an arena, they typically follow walls to a single corner and stay there. However, our thigmotaxic robots followed walls but typically circumnavigated the entire arena, contacting all corners, and exhibiting asymmetric corner behavior. After observing the latter behavior in robots, we found that rat pups also exhibited asymmetric corner behavior. Thus, our robotic experiments, while not quantitatively matching pup behavior, led to the discovery of a previously unrecognized pattern of behavior in rat pups. This illustrates the value of models in leading to discovery of new patterns of behavior in the system modeled. Our results also show that simple thigmotaxic architectures alone may not explain pup behavior in an arena.

Attachment in rat pups, an experimental approach

John Bowlby's attachment theory states that attachment behavior has been strengthened throughout evolution as a consequence of its adaptive value. We investigated the presence of attachment-like behavior in rat pups, by offering a choice between the home nest and a same aged other nest. Rat pups showed an increase of preference for the home nest during the second week and the first half of the third week. After that a preference for the other home side developed. Control experiments showed that the results were not due to repeated testing. Possible explanations of the results are discussed in light of renewed criteria for attachment in animal experiments. It is concluded that a primitive and temporary form of attachment in rats cannot be excluded.

Early NMDA receptor blockade impairs defensive behavior and increases cell proliferation in the dentate gyrus of developing rats.

These studies were conducted to determine whether (a) early N-methyl-D-aspartate (NMDA) receptor blockade impairs defensive behavior and (b) a relationship exists between defensive behavior and the production of granule cells in the dentate gyrus. Rat pups were treated with different doses of the NMDA receptor antagonist CGP 43487 on postnatal day (P) 5, and their behavior was observed following exposure to an unfamiliar adult male rat, a potential predator, on P13, P20, and P30. A dose-dependent impairment in freezing behavior was observed in rat pups treated with NMDA receptor antagonist on P13, P20, but not P30. Moreover, a dose-dependent increase in the number of (3)H-thymidine-labeled cells in the dentate gyrus was detected following CGP 43487 treatment, suggesting that an inverse relationship exists between cell proliferation and freezing behavior in rat pups following NMDA receptor blockade.

P.6.001 - The development of home-seeking behavior in rat pups

P.6.001 - The development of home-seeking behavior in rat pups