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PubMed2003

Pregnancy-stimulated neurogenesis in the adult female forebrain mediated by prolactin.

Neurogenesis occurs in the olfactory system of the adult brain throughout life, in both invertebrates and vertebrates, but its physiological regulation is not understood. We show that the production of neuronal progenitors is stimulated in the forebrain subventricular zone of female mice during pregnancy and that this effect is mediated by the hormone prolactin. The progenitors then migrate to produce new olfactory interneurons, a process likely to be important for maternal behavior, because olfactory discrimination is critical for recognition and rearing of offspring. Neurogenesis occurs even in females that mate with sterile males. These findings imply that forebrain olfactory neurogenesis may contribute to adaptive behaviors in mating and pregnancy.

Animals↗
PubMed2005

Egg dumping in insects.

Females that place eggs under the care of conspecifics have been labeled egg dumpers. Egg dumping is an effective reproductive alternative that lowers risks for, and has the potential to increase fecundity in, its practitioners. Although insect egg dumpers can be social parasites of the maternal behavior of egg recipients, dumping is more likely to be a viable reproductive alternative when the costs to egg recipients are low and thus the defense by potential hosts against egg dumping intrusions is minimal. These conditions are met in insects that guard only eggs or in insects whose eggs hatch into self-supporting precocial young that need little beyond defense from parents. When this is the case, egg dumping is favored by natural and/or kin selection as a mechanism by which dumpers can avoid parental risks and increase fecundity, and egg recipients can enhance offspring survival by diluting predation.

Animals↗
PubMed2002

Classical conditioning of breathing pattern after two acquisition trials in 2-day-old mice.

The aim of the present study was to test whether breathing pattern conditioning may occur just after birth. We hypothesized that sensory stimuli signaling the resumption of maternal care after separation may trigger an arousal and/or orienting response accompanied with concomitant respiratory changes. We performed a conditioning experiment in 2-day-old mice by using an odor (lemon) as the conditioned stimulus (CS) and maternal care after 1 h without the mother as the unconditioned stimulus (US). Each pup underwent two acquisition trials, in which the CS was presented immediately before (experimental paired group, n = 30) or 30 min before (control unpaired group, n = 30) contact with the mother. Conditioning was tested by using noninvasive whole body plethysmography to measure the respiratory response to the CS for 1 min. We found significantly stronger respiratory responses to the CS in the experimental group than in the control group. In contrast, somatomotor activity did not differ significantly between groups. Our results confirm the sensitivity of breathing to conditioning and indirectly support the hypothesis that learned feedforward processes may complement feedback pathways during postnatal maturation of respiratory control.

Animals↗
PubMed1975

Hypothalamic norepinephrine: concentration and metabolism during pregnancy and lactation in the rat.

Both norepinephrine (NE) and its major metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), were assayed in rat hypothalamus during selected stages of pregnancy and lactation. No changes were observed in the concentration of either NE or MHPG at 5, 15 or 21 days' gestation. However, with 8-15 h after parturition, the concentration of NE decreased sharply while that of MHPG showed a correspondingly sharp increase. The possible significance of such change in hypothalamic catecholamine activity was considered in relation to parturition, postpartum estrus and onset of maternal behavior.

Animals↗
PubMed1992

Hormonal regulation of medial preoptic mu-opiate receptor density before and after parturition.

Endogenous opioid peptides acting in the medial preoptic area (MPOA) appear to be involved in the regulation of maternal behavior in lactating rats. Moreover, it is known that the density of mu-opiate receptors in the MPOA is elevated during pregnancy, but decreases during lactation. In the first experiment of this study, mu-receptor density in the preoptic area was examined across the periparturitional period on gestation days 18, 20 and 22, at 1 h postpartum and on postpartum days 1 and 12. The effect of pregnancy during lactation on mu-receptor density was also assessed. In addition, plasma hormone concentration of estradiol (E2), progesterone (P), and prolactin (PRL) were determined. While plasma P levels decreased and PRL levels increased prior to parturition, MPOA mu-receptor density remained elevated until 24 h after parturition before declining to reach a level similar to that of ovariectomized control animals. Receptor density was significantly correlated with PRL levels only in gestation day 22 animals, when PRL levels were highest. MPOA mu-receptor density was low at postpartum day 12 whether or not the animal was pregnant. No effects were observed in the adjacent lateral preoptic area in any group. In the second experiment, the effect of hormonal manipulation on preoptic opiate receptor density was examined at various times after removal of Silastic capsules containing P following sustained E2/P exposure. While P levels decreased abruptly following capsule removal, MPOA receptor density declined more gradually. The results are consistent with the hypothesis that a reduction of mu-receptor density occurs in the MPOA following parturition by receptor turnover in the absence of sufficient hormonal stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Linking nutrition and education: a cross-generation model.

Psychosocial influences, such as the family or the school, and biologic influences, such as nutrition or the presence of environmental toxins, can be viewed as elements of a child's overall environment. Family and school influences define dimensions of the child's psychosocial environment whereas nutrition and exposure to toxins define dimensions of the child's bioecologic environment. This paper presents a cross-generation model specifying both the nature and consequences of linkages between the psychosocial and bioecologic environments, with specific reference to schooling, nutrition, and development. Data from two studies done in Egypt and Peru are used to illustrate this model, showing how duration of breastfeeding and quality of the young child's diet are positively associated with higher levels of maternal education and intelligence.

Child Nutritional Physiological Phenomena↗
PubMed2005

Out of Tanganyika: genesis, explosive speciation, key-innovations and phylogeography of the haplochromine cichlid fishes.

BACKGROUND: The adaptive radiations of cichlid fishes in East Africa are well known for their spectacular diversity and their astonishingly fast rates of speciation. About 80% of all 2,500 cichlid species in East Africa, and virtually all cichlid species from Lakes Victoria (approximately 500 species) and Malawi (approximately 1,000 species) are haplochromines. Here, we present the most extensive phylogenetic and phylogeographic analysis so far that includes about 100 species and is based on about 2,000 bp of the mitochondrial DNA. RESULTS: Our analyses revealed that all haplochromine lineages are ultimately derived from Lake Tanganyika endemics. We find that the three most ancestral lineages of the haplochromines sensu lato are relatively species poor, albeit widely distributed in Africa, whereas a fourth newly defined lineage - the 'modern haplochromines' - contains an unparalleled diversity that makes up more than 7% of the worlds' approximately 25,000 teleost species. The modern haplochromines' ancestor, most likely a riverine generalist, repeatedly gave rise to similar ecomorphs now found in several of the species flocks. Also, the Tanganyikan Tropheini are derived from that riverine ancestor suggesting that they successfully re-colonized Lake Tanganyika and speciated in parallel to an already established cichlid adaptive radiation. In contrast to most other known examples of adaptive radiations, these generalist ancestors were derived from highly diverse and specialized endemics from Lake Tanganyika. A reconstruction of life-history traits revealed that in an ancestral lineage leading to the modern haplochromines the characteristic egg-spots on anal fins of male individuals evolved. CONCLUSION: We conclude that Lake Tanganyika is the geographic and genetic cradle of all haplochromine lineages. In the ancestors of the replicate adaptive radiations of the 'modern haplochromines', behavioral (maternal mouthbrooding), morphological (egg-spots) and sexually selected (color polymorphism) key-innovations arose. These might be - together with the ecological opportunity that the habitat diversity of the large lakes provides - responsible for their evolutionary success and their propensity for explosive speciation.

Animals↗
PubMed1983

Brain beta-endorphin during pregnancy, parturition, and the postpartum period.

Brain beta-endorphin (beta-EP) was measured in the rat during pregnancy, parturition, and the postpartum period. beta-EP increased in the hypothalamus, midbrain, and amygdala during gestation and remained elevated through delivery until 1-2 days postpartum. The concentration of beta-EP increased in the hypothalamus from 31.8 +/- 1.4 (+/- SE) ng/mg protein in nonpregnant controls to 41.4 +/- 1.8 and 39.2 +/- 1.9 during early (8-10 days) and late (18-20 days) pregnancy, respectively, and in the midbrain from 3.20 +/- 0.17 to 5.21 +/- 0.30 and 5.25 +/- 0.64 ng/mg protein (P less than 0.01). In another experiment, the brain content of beta-EP expressed as nanograms per region, increased from 12.6 +/- 0.29 to 14.7 +/- 0.33 in the hypothalamus, from 4.09 +/- 0.44 to 6.03 +/- 0.34 in the midbrain, and from 0.93 +/- 0.11 to 1.32 +/- 0.06 ng in the amygdala at 16-17 days of gestation compared with that in nonpregnant controls (P less than 0.01). When hypothalamic beta-EP was measured 1 week postpartum in lactating and nonlactating rats, a significant decline in the beta-EP concentration of both groups was noted compared with that measured during pregnancy; beta-EP levels were similar in the lactating and nonlactating rats. We conclude that pregnancy and parturition are associated with significant changes in brain beta-EP and suggest that beta-EP of central rather than peripheral origin may mediate changes in pain perception and maternal behavior during pregnancy.

Animals↗
PubMed1983

Dorsal raphe-hypothalamic projections provide the stimulatory serotonergic input to suckling-induced prolactin release.

The present study was carried out to determine whether dorsal raphe serotonergic neurons are involved in the regulation of suckling-induced PRL release. Neurotoxin lesions were placed stereotaxically in lactating rats on day 1 of lactation by 5,7-dihydroxytryptamine microinjection into the dorsal raphe (DR), median raphe (MR), or superior colliculus (SC), an area devoid of serotonergic perikarya. Litters were adjusted to eight pups each and weighed daily to determine litter growth rates. On day 7 of lactation, litters were separated from mothers for 8 h, after which six healthy foster pups were provided for a 30-min suckling stimulus. Animals were killed by decapitation immediately after suckling, plasma was collected for RIA of PRL, and brains were frozen and dissected for determination of hypothalamic, caudate, and hippocampal serotonin (5-HT) using the enzymatic-isotopic assay procedure. Litter growth rates from days 1-7 of lactation were significantly different among lesion groups (P less than 0.005), with litters from SC-lesioned animals (SCL) growing similarly to the sham group (sham, 0.924; SCL, 0.941 g/pup . day). In contrast, growth rates of litters from both DR-lesioned (DRL) and MR-lesioned (MRL) animals were significantly depressed (DRL, 0.596; MRL, 0.449 g/pup . day; P less than 0.05 and P less than 0.01, respectively). 5-HT levels in hypothalamus, caudate nuclei, and hippocampus were similar in the sham and SCL groups, whereas hypothalamic 5-HT was depleted by 63% and 55%, respectively, in the DRL and MRL groups. Despite impairments in growth rate and litter survival in both the DRL and MRL groups, only DRL animals showed significant decrements in suckling-induced PRL release (DRL, 288 +/- 107; sham, 837 +/- 134 ng NIAMDD rat PRL RP-1/ml; P less than 0.05) after 5-HT-depleting lesions. The results suggest a specificity of function within the raphe system during lactation; DR 5-HT neurons which project to the hypothalamus provide stimulatory inputs to suckling-induced PRL release, whereas MR 5-HT neurons influence litter growth and survival via their role in maternal behavior.

Animals↗
PubMed1984

The effect of exteroceptive pup stimuli on the responsiveness of prolactin release mechanisms to suckling stimuli in the lactating rat.

In the lactating rat, the neural stimulus of suckling not only acutely releases PRL but also maintains the responsiveness of PRL regulatory mechanisms to subsequent nursing stimuli. Beginning near midlactation exteroceptive pup stimuli (ECS) can acutely release PRL. We have examined the capacity of this signal also to maintain the responsiveness of PRL release mechanisms to subsequent suckling stimuli. On day 14 postpartum lactating rats were either isolated from their young or exposed to ECS (without suckling) for approximately 24 h. When both groups were later nursed, plasma PRL of mothers earlier exposed to ECS rose significantly higher than that of subjects previously isolated from their young. Suckling produced a significant depletion in pituitary PRL and GH concentrations of ECS-exposed mothers; it did not produce a similar depletion in the pituitaries of the previously isolated group. When the pups were returned for suckling, ECS-exposed mothers began to nurse their pups substantially faster than did females of the isolated group. During the 6 h after nursing, the mammary glands of ECS-exposed mothers secreted milk at twice the rate of mammary glands of the isolated females. We conclude that ECS can maintain the capacity of neuroendocrine mechanisms to respond to galactopoetic hormone-releasing stimuli (consequently enhancing milk secretion) and support the maternal behavior pattern necessary for suckling to occur. As a result, ECS may become an important factor during later stages of lactation, compensating for the decline in suckling stimuli known to occur at that time.

Animals↗
PubMed1991

Monoclonal antibodies specific for rat relaxin. V. Passive immunization with monoclonal antibodies throughout the second half of pregnancy disrupts development of the mammary apparatus and, hence, lactational performance in rats.

There were two related objectives to this study. The first was to determine the influence of relaxin on development of the mammary apparatus (nipples and glands) during the second half of pregnancy. The second was to determine whether the relaxin-dependent development of the mammary apparatus was required for normal postpartum lactational performance. Both objectives were accomplished by neutralizing endogenous relaxin throughout the second half of pregnancy with a monoclonal antibody specific for rat relaxin (MCA1). MCA1 was administered iv to rats daily from days 12-22 of pregnancy. On day 22 the morphology of the mammary apparatus of MCA1-treated rats differed from that of controls; nipples were dramatically smaller, collagen fibers had significantly greater mean density and consistency, and elastin fibers had greater mean density, length, and interdigitation. In addition, the mean number of alveoli surrounding lactiferous ducts was significantly smaller in MCA1-treated rats than in controls. There were no differences between MCA1-treated rats and controls in the mean thickness of connective tissue surrounding ducts, the height or density of luminal cells lining lactiferous ducts, or the sizes of either adipocytes or arteries. To examine lactational performance, MCA1-treated and control rats were cesarean sectioned between 2100-2400 h on day 22 of pregnancy and given foster pups born of untreated intact donors. Although both MCA1-treated rats and control rats exhibited a high incidence of maternal behavior after cesarean delivery, mean pup weight and incidence of live pups declined markedly during days 1-5 of fosterage in MCA1-treated rats compared to controls. Furthermore, unlike controls, there was no observable postpartum nipple development in MCA1-treated rats by day 5 of fosterage. Mammary glands obtained from MCA1-treated rats on day 5 of fosterage had markedly lower mean weight than controls. This study demonstrates that passive immunization of endogenous relaxin throughout the second half of pregnancy disrupts development of the nipples and mammary glands in the rat. Moreover, it establishes that relaxin's effects on the development of the mammary apparatus during pregnancy are essential for growth and survival of the young during lactation.

Animals↗