Maternal behavior in the mouse: effect of estrogen and progesterone

The administration of 100 μg and 50 μg of estradiol benzoate for 5 consecutive days to adult, nulliparous. Rockland-Swiss mice that previously exhibited maternal behavior resulted in a loss of such behavior. The effect of estradiol was temporary since normal maternal activities were exhibited when the animals were retested two weeks after the termination of hormone treatment. Treatment with 5 μg and 0.5 μg estradiol benzoate did not significantly affect maternal behavior. Progesterone treatment at dosages of 1000 μg and 500 μg was without affect.     

Maternal behavior: differences between mother and virgin mice as a function of the testing procedure

Retrieval by lactating and virgin mice was compared in a straight alley and a T-maze. In both test situations the retrieval performance of the lactating mouse was superior to that of the virgin animal. No discrimination was seen between a live pup and a dead pup; a rubber toy, however, was retrieved least by both the lactating and virgin mice. Contrary to previous results, these experiments demonstrate a significant difference in maternal behavior between lactating and virgin mice.     

Maternal care affects the development of maternal behavior in inbred mice

The present study investigated the effects of variations in maternal behavior on the development of maternal behavior of female offspring in BALB/c and CBA/Ca inbred mice. In Experiment 1, we conducted fostering within or between the two strains and observed the maternal behaviors of mothers and female offspring for 2 weeks postpartum. Although fostering changed the maternal behavior of mothers in both strains, CBA mothers generally showed greater frequency of nursing posture and pup licking than BALB mothers. BALB female offspring reared by CBA mothers showed more body licking than those reared by BALB mothers, whereas fostering did not affect the maternal behavior of CBA female offspring. In Experiment 2, we examined the maternal behavior of females of F1 hybrids derived from reciprocal crosses between the two strains to confirm the maternal effect demonstrated in Experiment 1. Female F1 hybrids from CBA mothers showed more arched‐back nursing, body licking, and nest building than those from BALB mothers. These results suggested that maternal care affect the development of maternal behavior in inbred mice, though the contributions of genetic and prenatal factors cannot be ignored. © 2009 Wiley Periodicals, Inc. Dev. Psychobiol 51: 345–357, 2009.     

Maternal behavior in the rat: aspects of concaveation and neonatal androgen treatment

Evidence is presented to show that maternal responsiveness of lactating females differs from concaveation-induced maternal responsiveness of gonadectomized male and female rats of the Long-Evans strain. When rat pups were placed in a runway extension of the home cage lactating females retrieved the pups to a significantly greater degree than did the concaveation treated animals. The present experiment failed to show significant differences in concaveation-induced maternal responsiveness in gonadectomized males, females and neonatally androgenized females.     

Maternal behavior in male rats: Critical times for the suppressive action of androgens

To determine whether the first day of life is the only period during infancy when removal of the testes permanently alters maternal behavior in rats, male Sprague-Dawley rats were castrated on either Day 1, 5, 10, 25 or 70 of life and were tested as adults for maternal behavior following testosterone replacement. Males castrated on Day 1, 5 or 10 responded significantly sooner to pups and spent longer times exhibiting maternal behavior than did males castrated on Day 25 or later. However removal of the testes on the first day of life was maximally effective. Treatment with testosterone neither inhibited nor facilitated maternal behavior. Thus there is no one critical period in infancy for differentiation of the neural substrate for maternal behavior, although removal of androgen at birth is maximally effective for the onset of maternal behavior in the adult.     

Multivariate and behavior genetic analysis of avoidance of complex visual stimuli and activity in recombinant inbred strains of mice

Sixty-six mice of 11 genetic stocks (the Bailey recombinant inbred strains CXBD, CXBE, CXBG, CXBH, CXBI, CXBJ, CXBK; their progenitor strains, BALB/cBy and C57BL/6By; and the reciprocal hybrids, B6CF and CB6F) were tested in a two-compartment apparatus and in a shuttlebox, with five measures taken relating to activity and to approaches to novel and complex stimuli. A factor analysis of these measures revealed two factors, the first involving behavior relating to novel stimuli and the second relating to locomotor activity. In a second experiment, 132 mice of the same strains were tested on four of the measures used previously. On the two measures which had high loadings on the first factor and very low loadings on the second, it was possible to determine a strain distribution pattern (SDP), with the same SDP being found for both measures. When confirmed by testing mice from two congenic histocompatibility strains H(w54) and H(w80), we were able to determine that avoidance of novel/complex stimuli (neophobia) is controlled by a gene or genes at chromosomal segmentsH-24 ^c andH-1 ^b . It was also found that a polygenic model is consistent with behavior measured by the second (activity) factor.Supported by a Miami University Faculty Research Grant to E. C. S. and NIH Research Grant HD 05860 from the National Institute of Child Health and Human Development to B. E. E.Visiting Investigator at The Jackson Laboratory Summer 1975The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Acute endocrine correlates of attack by lactating females in male mice: effects on plasma prolactin, luteinizing hormone and corticosterone levels

Immediately following defeat inflicted by lactating Rockland-Swiss (R-S) albino mice, adult R-S male mice exhibited significant reductions in circulating prolactin (PRL) and luteinizing hormone (LH), but not corticosterone (CORT). These results suggest that acute neuroendocrine responses to intersex competition may be as dramatic as those previously reported for intermale encounters.     

Maternal behavior priming in virgin and caesarean-delivered Long-Evans rats: effects of brief contact or continuous exteroceptive pup stimulation

The effects of 8 days of prior exposure to pups (Priming) in the form of continuous exteroceptive (smell, sight and sound), or 15 min/day physical access (taste and touch possible) stimulation on the subsequent latency to become maternal during cohabitation with pups (concaveation) was studied in Long-Evans female rats. Brief daily access was effective in hastening the onset of maternal behavior only in those virgins which engaged in pup licking during Priming and in maintaining short-latency maternal responsiveness only in those day 21 pregnancy-terminated, thelectomized rats which initiated maternal behavior during Priming. Exteroceptive stimulation was ineffective in both virgins and caesarean-sectioned rats. These findings stress the importance of physical interactions with pups (unrelated to nipple stimulation) for the development of nurturance.     

Different mossy fiber patterns in two inbred strains of mice: a functional hypothesis

Quantitative and qualitative evaluations of the distribution of mossy fiber terminals in the hippocampal region inferior were performed in two inbred strains of mice, SECRe/J and C57BL/6, known to have different learning abilities. The results confirmed previous observations showing that there are fewer mossy fiber terminals along basal dendrites of the CA3 pyramidal cells in the high performer strain (SECRe/J). One additional, qualitative difference between the strains was found near the hilus and in particular at dorsal levels. Thus strands of mossy fiber terminals connecting the infra- and suprapyramidal mossy fiber layers were more significant and more randomly oriented in the C57BL/6 strain than in SECRe/J. In an otherwise laminar structure like the hippocampus this might have a similar functional importance as the quantitative differences.     

Open-field behavior in mice: Generality of results from a diallel analysis of replicate selected lines

Data from a diallel cross of six lines composing a replicated selection study for open-field behavior in mice are reanalyzed to investigate the generality of the findings. The results support the hypothesis that only additive variation would be found for open-field behavior if additional selection lines were derived from the same foundation population.     

Maternal postpartum behavior and the emergence of infant-mother and infant-father synchrony in preterm and full-term infants: the role of neonatal vagal tone

Relations between maternal postpartum behavior and the emergence of parent-infant relatedness as a function of infant autonomic maturity were examined in 56 premature infants (birthweight = 1000-1500 g) and 52 full-term infants. Maternal behavior, mother depressive symptoms, and infant cardiac vagal tone were assessed in the neonatal period. Infant-mother and infant-father synchrony, maternal and paternal affectionate touch, and the home environment were observed at 3 months. Premature birth was associated with higher maternal depression, less maternal behaviors, decreased infant alertness, and lower coordination of maternal behavior with infant alertness in the neonatal period. At 3 months, interactions between premature infants with their mothers and fathers were less synchronous. Interaction effects of premature birth and autonomic maturity indicated that preterm infants with low vagal tone received the lowest amounts of maternal behavior in the postpartum and the least maternal touch at 3 months. Infant-mother and infant-father synchrony were each predicted by cardiac vagal tone and maternal postpartum behavior in both the preterm and full-term groups. Among preterm infants, additional predictors of parent-infant synchrony were maternal depression (mother only) and the home environment (mother and father). Findings are consistent with evolutionary perspectives on the higher susceptibility of dysregulated infants to rearing contexts and underscore the compensatory mechanisms required for social-emotional growth under risk conditions for parent-infant bonding.     

Genetic analysis of the circadian oviposition rhythm inDrosophila melanogaster: Effects of drift in laboratory strains

Under photoperiodic conditions, flies recently collected in nature exhibit, at the beginning of the scotophase, an oviposition peak which has a higher amplitude in Afrotropical than in European temperate populations. Several old laboratory strains failed, however, to show this peak. In each cross between genetically different strains, the oviposition curves of F₁ and F₂ were usually close to the midparent curve. Ten isofemale lines from an Afrotropical populations were submitted to inbreeding and drift. After 100 generations, two of the four surviving lines had retained the high peak typical of the origin population while the two others had lost it. Chromosome substitutions between these lines demonstrated a polygenic inheritance with a significant effect of the three major chromosomes. Presumably, the variations of amplitude of the oviposition peak were not caused by a modification of the ovarian activity but by a behavioral change toward the external signals of the environment.     

Ethanol-induced anesthesia in inbred strains of long-sleep and short-sleep mice: A genetic analysis of repeated measures using censored data

We present a repeated-measures, genetic analysis of ethanol-induced anesthesia (sleep time) in mice from the inbred long-sleep (ILS) and short-sleep (ISS) strains of mice and their derived F₁ and F₂ generations. Mice (totalN>1300) were administered a 4.1 g/kg intraperitoneal dose of ethanol at two times, 7 to 10 days apart. A method suggested by Cohen was used to analyze the resulting data, which contained a known number of unmeasured observations. A genetic model that included both additive and epistatic parameters fitted the adjusted data well. A novel procedure, for estimating heritability, based on a comparison of repeatability coefficients from the isogenic and genetically segregating populations, was also employed. Results of this analysis suggested that the heritability for individual measurements of sleep time is about. 30, whereas the heritability of average scores is about. 40. Results of this analysis also confirm that the ILS and ISS strains differ for genes at seven or more loci that influence sleep time. Since the ILS and ISS were derived by inbreeding the LS and SS lines, these results further suggest that almost all of the genetic variation present in the selected lines have been maintained in the ILS and ISS strains.To whom correspondence should be addressed at Institute for Behavioral Genetics.     

Endocrine induction of intermale aggression in mice: a comparison of hormonal regimens and their relationship to naturally occurring behavior

The level of intermale-like fighting behavior induced in female mice by various regimens of gonadal hormones known to establish aggression was compared. Regardless of whether the animals were exposed to testosterone propionate on the day of birth, the highest aggression scores were observed following chronic testosterone exposure in adult life. Females so treated also exhibited significantly more aggression than intact males. The least effective regimen was neonatal exposure to estradiol benzoate followed by long-term exposure of the adult to testosterone. Lastly, while castrated adult males were less likely to display aggressive behavior, those that fought did so at a level comparable to that of intact males.     

Exposure to ethanol during pregnancy in mice: potential importance of dose for the development of tolerance in offspring

CD-1 albino mice were given Portagen-10 percent ethanol (ETOH) or isocaloric Portagen-sucrose during pregnancy to determine if tolerance developed in utero and to describe the temporal pattern of its decline postnatally. ETOH mothers did not significantly increase their consumption of ETOH but gained in body weight during pregnancy, showed no signs in the open field of withdrawal from ETOH shortly after delivery and showed less pup-caring behavior than pair-fed controls (PFC). Among offspring 1, 3, 10, 25 and 60 days old, only 25-day old ETOH pups metabolized and cleared an anesthetic dose of ETOH more efficiently than PFC animals, suggesting the absence of Dispositional Tolerance in the other animals. PFC offspring 10 days old took significantly longer to lose the righting reflex than their ETOH counterparts following the anesthetic dose of ETOH, the difference being opposite that which would suggest the occurrence of Adaptive Tolerance. Data are discussed primarily in terms of decreases in dose of ETOH to which mothers and fetuses were exposed during pregnancy.     

Maternal colonization and early-onset neonatal bacterial sepsis in the Gambia,West Africa: a genomic analysis of vertical transmission

ObjectivesTo define bacterial aetiology of neonatal sepsis and estimate the prevalence of neonatal infection from maternal genital tract bacterial carriage among mother-newborn pairs.MethodsWe carried out a cross-sectional study of newborns with clinical sepsis admitted to three hospitals in the Gambia neonatal wards. Neonatal blood cultures and maternal genital swabs were obtained at recruitment. We used whole-genome sequencing to explore vertical transmission for neonates with microbiologically confirmed bloodstream infection by comparing phenotypically-matched paired neonatal blood cultures and maternal genital tract bacterial isolates.ResultsWe enrolled 203 maternal-newborn pairs. Two-thirds (67%; 137/203) of neonates presented with early-onset sepsis (days 0–6 after birth) of which 26% (36/137) were because of a clinically-significant bacterial pathogen. Blood culture isolates from newborns with early-onset sepsis because of Staphylococcus aureus (n = 5), Klebsiella pneumonia (n = 2), and Enterococcus faecalis (n = 1), phenotypically matched their maternal genital tract isolates. Pairwise single-nucleotide variants comparisons showed differences of 12 to 52 single-nucleotide variants only between maternal and newborn S. aureus isolates, presumably representing vertical transmission with a transmission rate of 14% (5/36).ConclusionsWe found a low prevalence of vertical transmission of maternal genital tract colonization in maternal-newborn pairs for early-onset neonatal sepsis in the West African context. Identifying infection acquisition pathways among newborns is essential to prioritize preventive interventions, which could be targeted at the mother or infection control in the hospital environment, depending on the major pathways of transmission.     

Genetically determined differences in noradrenergic input to the brain cortex: a histochemical and biochemical study in two inbred strains of mice.

The C57 BL/6 and Balb/c strains of mice are characterized by their opposite behavioral responses in several tests. Since several central catecholaminergic systems could be involved, we have analyzed particularly the noradrenergic input to the frontal, parietal, hippocampal and cerebellar cortex in the two strains, using three different approaches. The fluorescence histochemical study revealed the presence of more numerous noradrenergic terminals in all the areas examined (except in the deep layers of the parietal cortex) and a higher number of catecholaminergic cell bodies in the locus coeruleus of the C57 BL/6 mice. Higher levels of norepinephrine were also found in the same cortical areas, except the parietal cortex. However, as indicated by the estimations of the activity of the isoproterenol-sensitive adenylate cyclase and the specific binding of [³H]dihydroalprenolol, there was no difference in the number and the affinity of β-adrenergic receptors in the cerebral cortex of the two strains. The higher density of the cortical noradrenergic innervation observed in the C57 BL/6 mice, which persisted in older animals, seems to be genetically determined.The marked difference in the extent of the dorsal noradrenergic pathway seen between the C57 BL/6 and Balb/c strains could thus make them a valuable model to further define the functional role of the dorsal noradrenergic system.     

Possible causal relationships between cerebellar patterns of foliation and hindlimb coordination in laboratory mice: a quantitative trait locus analysis

The cerebellum is involved in a large set of integrative functions including memory, affect, and motricity. The cerebellar patterns of foliation and their causal relationships with motricity were investigated via a wide genome scan approach and quantitative trait locus (QTL) strategy. QTLs were mapped in an F₂ population derived from NZB/B1NJ and C57BL/6By inbred strains of mice for cerebellar fissures in the four vermal lobules (intraculminate, uvula, declival, and intracentral) and for hindpaw slips in a bar crossing test. No linkage was detected for uvula and intracentral fissures. We found five QTLs linked to declival fissure: Cpfd-1q and Cpfd-2q (chromosome 1), Cpfd-3q (chromosome 5), Cpfd-4q (chromosome 9), and Cpfd-5q (chromosome 13). Two QTLs were also mapped for intraculminate fissure Cpfi-1q (chromosome 4) and Cpfi-2q (chromosome 1). Most of the confidence intervals of these QTLs included genes that were previously identified for their implication in the physiological mechanisms underlying cerebellar patterns of foliation. Only one significant QTL was found for the measure of hindpaw coordination (Tne-1q). It was linked with Cpfd-1q and Cpfd-2q on the telomeric part of chromosome 1.     

A developmental genetic analysis of locomotor activity in mice: Maternal effects in the BALB/c and C57BL/6 strains and heredity in F1 hybrids

Continuous recording of locomotor activity of mice during 48 h in seminatural enclosures was performed at 21 and 75 days of age, on the same individuals. Four groups of inbred subjects were compared for amount of locomotor activity and its daily distribution: in both BALB/C ( = BALB) and C57BL/6 ( = C57) strains, pups were either fostered by a mother of their own strain or crossfostered to a mother of the other. In addition, two reciprocal F₁'s were compared to the parental strains. While no significant effect of crossfostering to a C57 dam appeared in BALB mice, 21-day-old C57 crossfostered to a BALB dam were more active and more nocturnal than those reared by a C57 dam. In C57 mice the change in activity level between 21 and 75 days was also affected by crossfostering. Reciprocal F₁ hybrids did not differ. A BALB pattern was dominant at 21 days for amount of activity and for change between 21 and 75 days. For daily distribution of activity, F₁ hybrids were BALB-like at weaning and C57-like (with heterosis) in adulthood.