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Interactions with the young down-regulate adult olfactory neurogenesis and enhance the maturation of olfactory neuroblasts in sheep mothers.

Brus M, Meurisse M, Keller M, Lévy F - Front Behav Neurosci (2014)

Bottom Line: In addition, a morphological analysis was performed by measuring the dendritic arbor of neuroblasts in both structures.We showed that the postpartum period was associated with a decrease in olfactory and hippocampal adult neurogenesis.Our assumption is that fewer new neurons decrease cell competition in the olfactory bulb and enhance maturation of those new neurons selected to participate in the learning of the young odor.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR 85, Physiologie de la Reproduction et des Comportements Nouzilly, France ; CNRS, UMR 7247 Nouzilly, France ; Université François Rabelais Tours, France ; IFCE Nouzilly, France.

ABSTRACT
New neurons are continuously added in the dentate gyrus (DG) and the olfactory bulb of mammalian brain. While numerous environmental factors controlling survival of newborn neurons have been extensively studied, regulation by social interactions is less documented. We addressed this question by investigating the influence of parturition and interactions with the young on neurogenesis in sheep mothers. Using Bromodeoxyuridine, a marker of cell division, in combination with markers of neuronal maturation, the percentage of neuroblasts and new mature neurons in the olfactory bulb and the DG was compared between groups of parturient ewes which could interact or not with their lamb, and virgins. In addition, a morphological analysis was performed by measuring the dendritic arbor of neuroblasts in both structures. We showed that the postpartum period was associated with a decrease in olfactory and hippocampal adult neurogenesis. In the olfactory bulb, the suppressive effect on neuroblasts was dependent on interactions with the young whereas in the DG the decrease in new mature neurons was associated with parturition. In addition, dendritic length and number of nodes of neuroblasts were significantly enhanced by interactions with the lamb in the olfactory bulb but not in the DG. Because interactions with the young involved learning of the olfactory signature of the lamb, we hypothesize that this learning is associated with a down-regulation in olfactory neurogenesis and an enhancement of olfactory neuroblast maturation. Our assumption is that fewer new neurons decrease cell competition in the olfactory bulb and enhance maturation of those new neurons selected to participate in the learning of the young odor.

No MeSH data available.


Related in: MedlinePlus

Time table and protocol design. All ewes received four intravenous injections of BrdU (20 mg/kg, 1 injection/day) 4 months before sacrifice. In the two parturient groups (“With Lamb” and “No Lamb”), BrdU injections were performed 1 month after fecundation. In the ”With Lamb” group (n = 5), ewes could interact with her lamb and maternal behavior was observed at 0, 6 and 24 h after parturition for 10 min each and selectivity test was performed at 2 days postpartum just before sacrifice. In the “No Lamb” group (n = 6), lambs were removed just after delivery. Virgin group (n = 6) is composed of iparous ewes.
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Figure 1: Time table and protocol design. All ewes received four intravenous injections of BrdU (20 mg/kg, 1 injection/day) 4 months before sacrifice. In the two parturient groups (“With Lamb” and “No Lamb”), BrdU injections were performed 1 month after fecundation. In the ”With Lamb” group (n = 5), ewes could interact with her lamb and maternal behavior was observed at 0, 6 and 24 h after parturition for 10 min each and selectivity test was performed at 2 days postpartum just before sacrifice. In the “No Lamb” group (n = 6), lambs were removed just after delivery. Virgin group (n = 6) is composed of iparous ewes.

Mentions: Three groups of ewes were constituted (Figure 1). In parturient groups, mating was synchronized by the use of vaginal sponges containing 45 mg of fluorogestone acetate for 14 days followed by an intra-muscular injection of pregnant-mare-stimulating gonadotropins to induce ovulation. Just after parturition, mothers were either left 48 h with their lambs in their individual pen in the same barn (“With Lamb” group, n = 5), or were separated from them for 48 h (“No Lamb” group, n = 6). After being separated from their lamb immediately after birth, ewes of the “No Lamb” group were placed in a different barn to avoid any contact with lambs and ewes were housed together in a large pen to avoid stress induced by separation from the young. All the ewes had never given birth before the study. Lambing occurred within a period of gestation of 149 ± 4 days. Against all expectations, at birth the lambs displayed low vigor preventing them from feeding normally, probably due to BrdU injections in early pregnancy. Thus, in the “With lamb” group, adoptions have been performed with newborn lambs provided by the flock of the research center. It has been well established in previous studies that adoption, when performed at birth, are without any consequences on the quality of the mother-young relationship in comparison to normal mother-young lambing (Keverne et al., 1983; Kendrick et al., 1991; Lévy et al., 2010). In this group, maternal behavior was observed for 10 min at 0, 6 and 24 h after parturition to completely ensure that maternal care was normally provided to lambs. At 2 days postpartum just before sacrifice, selectivity was tested by presenting an alien lamb to the mother and rejection and acceptance behaviors were recorded for 3 min. The alien lamb was then taken away and the ewe was observed with her own lamb for an additional 3 min (Keller et al., 2004, 2005). These tests indicated that all the ewes of the “With Lamb” group were maternal and selective. The “Virgin” group (n = 6) was composed of iparous anoestrus ewes of similar age than the two parturient groups and housed together.


Interactions with the young down-regulate adult olfactory neurogenesis and enhance the maturation of olfactory neuroblasts in sheep mothers.

Brus M, Meurisse M, Keller M, Lévy F - Front Behav Neurosci (2014)

Time table and protocol design. All ewes received four intravenous injections of BrdU (20 mg/kg, 1 injection/day) 4 months before sacrifice. In the two parturient groups (“With Lamb” and “No Lamb”), BrdU injections were performed 1 month after fecundation. In the ”With Lamb” group (n = 5), ewes could interact with her lamb and maternal behavior was observed at 0, 6 and 24 h after parturition for 10 min each and selectivity test was performed at 2 days postpartum just before sacrifice. In the “No Lamb” group (n = 6), lambs were removed just after delivery. Virgin group (n = 6) is composed of iparous ewes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927075&req=5

Figure 1: Time table and protocol design. All ewes received four intravenous injections of BrdU (20 mg/kg, 1 injection/day) 4 months before sacrifice. In the two parturient groups (“With Lamb” and “No Lamb”), BrdU injections were performed 1 month after fecundation. In the ”With Lamb” group (n = 5), ewes could interact with her lamb and maternal behavior was observed at 0, 6 and 24 h after parturition for 10 min each and selectivity test was performed at 2 days postpartum just before sacrifice. In the “No Lamb” group (n = 6), lambs were removed just after delivery. Virgin group (n = 6) is composed of iparous ewes.
Mentions: Three groups of ewes were constituted (Figure 1). In parturient groups, mating was synchronized by the use of vaginal sponges containing 45 mg of fluorogestone acetate for 14 days followed by an intra-muscular injection of pregnant-mare-stimulating gonadotropins to induce ovulation. Just after parturition, mothers were either left 48 h with their lambs in their individual pen in the same barn (“With Lamb” group, n = 5), or were separated from them for 48 h (“No Lamb” group, n = 6). After being separated from their lamb immediately after birth, ewes of the “No Lamb” group were placed in a different barn to avoid any contact with lambs and ewes were housed together in a large pen to avoid stress induced by separation from the young. All the ewes had never given birth before the study. Lambing occurred within a period of gestation of 149 ± 4 days. Against all expectations, at birth the lambs displayed low vigor preventing them from feeding normally, probably due to BrdU injections in early pregnancy. Thus, in the “With lamb” group, adoptions have been performed with newborn lambs provided by the flock of the research center. It has been well established in previous studies that adoption, when performed at birth, are without any consequences on the quality of the mother-young relationship in comparison to normal mother-young lambing (Keverne et al., 1983; Kendrick et al., 1991; Lévy et al., 2010). In this group, maternal behavior was observed for 10 min at 0, 6 and 24 h after parturition to completely ensure that maternal care was normally provided to lambs. At 2 days postpartum just before sacrifice, selectivity was tested by presenting an alien lamb to the mother and rejection and acceptance behaviors were recorded for 3 min. The alien lamb was then taken away and the ewe was observed with her own lamb for an additional 3 min (Keller et al., 2004, 2005). These tests indicated that all the ewes of the “With Lamb” group were maternal and selective. The “Virgin” group (n = 6) was composed of iparous anoestrus ewes of similar age than the two parturient groups and housed together.

Bottom Line: In addition, a morphological analysis was performed by measuring the dendritic arbor of neuroblasts in both structures.We showed that the postpartum period was associated with a decrease in olfactory and hippocampal adult neurogenesis.Our assumption is that fewer new neurons decrease cell competition in the olfactory bulb and enhance maturation of those new neurons selected to participate in the learning of the young odor.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR 85, Physiologie de la Reproduction et des Comportements Nouzilly, France ; CNRS, UMR 7247 Nouzilly, France ; Université François Rabelais Tours, France ; IFCE Nouzilly, France.

ABSTRACT
New neurons are continuously added in the dentate gyrus (DG) and the olfactory bulb of mammalian brain. While numerous environmental factors controlling survival of newborn neurons have been extensively studied, regulation by social interactions is less documented. We addressed this question by investigating the influence of parturition and interactions with the young on neurogenesis in sheep mothers. Using Bromodeoxyuridine, a marker of cell division, in combination with markers of neuronal maturation, the percentage of neuroblasts and new mature neurons in the olfactory bulb and the DG was compared between groups of parturient ewes which could interact or not with their lamb, and virgins. In addition, a morphological analysis was performed by measuring the dendritic arbor of neuroblasts in both structures. We showed that the postpartum period was associated with a decrease in olfactory and hippocampal adult neurogenesis. In the olfactory bulb, the suppressive effect on neuroblasts was dependent on interactions with the young whereas in the DG the decrease in new mature neurons was associated with parturition. In addition, dendritic length and number of nodes of neuroblasts were significantly enhanced by interactions with the lamb in the olfactory bulb but not in the DG. Because interactions with the young involved learning of the olfactory signature of the lamb, we hypothesize that this learning is associated with a down-regulation in olfactory neurogenesis and an enhancement of olfactory neuroblast maturation. Our assumption is that fewer new neurons decrease cell competition in the olfactory bulb and enhance maturation of those new neurons selected to participate in the learning of the young odor.

No MeSH data available.


Related in: MedlinePlus