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Nielsen B.L.,French National Institute for Agricultural Research | Jerome N.,French National Institute for Agricultural Research | Saint-Albin A.,French National Institute for Agricultural Research | Ouali C.,French National Institute for Agricultural Research | And 9 more authors.
Applied Animal Behaviour Science | Year: 2016

Three experiments were conducted to investigate if sexual experience affects the behavioural response of male rats to natural oestrus odours and constituent odorants. In the first experiment, 16 male Brown Norway rats were exposed before and after sexual training to four odours (1-hexanol (herb odour), a ketone mixture, and faeces from mares and rats in oestrus) presented one at a time to individual rats during a 30-min test. More penile erections were observed during tests when rats were exposed to the two types of faeces as well as the ketone mixture compared to 1-hexanol, both when sexually naïve (P = 0.032) and experienced (P = 0.002). In the second experiment, 30 male rats were tested using a habituation/dishabituation protocol. The rats were able to distinguish the ketone mixture used in Experiment 1 from another single-molecule ketone (P < 0.001), which has previously been found to elicit erections in male rats. Finally in the third experiment, five faeces samples each from male, oestrus and di-oestrus rats and horses (N = 30) were analysed using gas chromatography-mass spectrometry (GC-MS) for the presence of three ketones and 1-hexanol using menthol as an added calibrating compound. Although significant intra-species differences in ketone composition were found between faeces from males and females in oestrus and di-oestrus, these differences were dissimilar across species. Also, 1-hexanol was present in all six faeces types. The results indicate that the ketones used may not be specific oestrus odorants, but may share volatile characteristics with natural oestrus odours. These findings are discussed in relation to oestrus odours and their potential commonality across mammalian species. © 2016 Elsevier B.V.

Batailler M.,CNRS Physiology of Reproduction and Behaviors | Batailler M.,University of Tours | Batailler M.,Institute Francais Du Cheval Et Of Lequitation Ifce | Droguerre M.,CNRS Physiology of Reproduction and Behaviors | And 8 more authors.
Journal of Comparative Neurology | Year: 2014

Neural stem and precursor cells persist postnatally throughout adulthood and are capable of responding to numerous endogenous and exogenous signals by modifying their proliferation and differentiation. Whereas adult neurogenesis has been extensively studied in the dentate gyrus of the hippocampal formation and in the subventricular zone adjacent to the wall of the lateral ventricles, we and others have recently reported constitutive adult neurogenesis in other brain structures, including the hypothalamus. In this study, we used immunohistochemistry to study the expression of the neuroblast marker doublecortin (DCX), and compared its expression pattern in adult ovine, mouse, and human hypothalamic tissues. Our results indicate that DCX-positive cells resembling immature and developing neurons occur in a wide range of hypothalamic nuclei in all three species, although with different distribution patterns. In addition, the morphology of DCX-positive cells varied depending on their location. DCX-positive cells near the third ventricle had the morphology of very immature neuroblasts, a round shape with no processes, whereas those located deeper in the parenchyma such as in the ventromedial nucleus were fusiform and showed a bipolar morphology. Extending this observation, we showed that among the cohort of immature neurons entering the ventromedial nucleus, some appeared to undergo maturation, as revealed by the partial colocalization of DCX with markers of more mature neurons, e.g., human neuronal protein C and D (HuC/D). This study provides further confirmation of the existence of an adult hypothalamic neurogenic niche and argues for the potential existence of a migratory path within the hypothalamus. © 2013 Wiley Periodicals, Inc.

Batailler M.,CNRS Physiology of Reproduction and Behaviors | Batailler M.,French National Center for Scientific Research | Batailler M.,University of Tours | Batailler M.,Institute Francais Du Cheval Et Of Lequitation Ifce | And 12 more authors.
Brain Structure and Function | Year: 2015

Adult neurogenesis, a process that consists in the generation of new neurons from adult neural stem cells, represents a remarkable illustration of the brain structural plasticity abilities. The hypothalamus, a brain region that plays a key role in the neuroendocrine regulations including reproduction, metabolism or food intake, houses neural stem cells located within a hypothalamic neurogenic niche. In adult sheep, a seasonal mammalian species, previous recent studies have revealed photoperiod-dependent changes in the hypothalamic cell proliferation rate. In addition, doublecortin (DCX), a microtubule-associated protein expressed in immature migrating neurons, is highly present in the vicinity of the hypothalamic neurogenic niche. With the aim to further explore the mechanism underlying adult sheep hypothalamic neurogenesis, we first show that new neuron production is also seasonally regulated since the density of DCX-positive cells changes according to the photoperiodic conditions at various time points of the year. We then demonstrate that cyclin-dependant kinase-5 (Cdk5) and p35, two proteins involved in DCX phosphorylation and known to be critically involved in migration processes, are co-expressed with DCX in young hypothalamic neurons and are capable of in vivo interaction. Finally, to examine the migratory potential of these adult-born neurons, we reveal the rostro-caudal extent of DCX labeling on hypothalamic sagittal planes. DCX-positive cells are found in the most rostral nuclei of the hypothalamus, including the preoptic area many of which co-expressed estrogen receptor-α. Thus, beyond the confirmation of the high level of neuron production during short photoperiod in sheep, our results bring new and compelling elements in support of the existence of a hypothalamic migratory path that is responsive to seasonal stimuli. © 2015 Springer-Verlag Berlin Heidelberg

Pinet-Charvet C.,CNRS Physiology of Reproduction and Behaviors | Pinet-Charvet C.,French National Center for Scientific Research | Pinet-Charvet C.,Institute Francais Du Cheval Et Of Lequitation Ifce | Pinet-Charvet C.,University of Tours | And 36 more authors.
Endocrinology | Year: 2016

Episodic release of GnRH is essential for reproductive function. In vitro studies have established that this episodic release is an endogenous property of GnRH neurons and that GnRH secretory pulses are associated with synchronization of GnRH neuron activity. The cellular mechanisms by which GnRHneurons synchronize remain largely unknown. There isnoclear evidence of physical coupling of GnRH neurons through gap junctions to explain episodic synchronization. However, coupling of glial cells through gap junctions has been shown to regulate neuron activity in their microenvironment. The present study investigated whetherglial cell communication throughgapjunctions plays a role in GnRH neuron activity and secretion in the mouse. Our findings show that Glial Fibrillary Acidic Protein-expressing glial cells located in the median eminence in close vicinity to GnRH fibers expressed Gja1 encoding connexin-43. To study the impact of glial-gap junction coupling on GnRH neuron activity, an in vitro model of primary cultures from mouse embryo nasal placodes was used. In this model, GnRH neurons possess a glial microenvironment and were able to release GnRH in an episodic manner. Our findings show that in vitro glial cells forming the microenvironment of GnRH neurons expressed connexin-43 and displayed functional gap junctions. Pharmacological blockade of thegapjunctions with 50μM18-α-glycyrrhetinic acid decreased GnRH secretion by reducing pulse frequency and amplitude, suppressed neuronal synchronization and drastically reduced spontaneous electrical activity, all these effects were reversed upon 18-α-glycyrrhetinic acid washout. Copyright © 2016 by the Endocrine Society.

Migaud M.,CNRS Physiology of Reproduction and Behaviors | Migaud M.,French National Center for Scientific Research | Migaud M.,University of Tours | Migaud M.,Institute Francais Du Cheval Et Of Lequitation Ifce | And 16 more authors.
Theriogenology | Year: 2016

During adulthood, the mammalian brain retains the capacity to generate new cells and new neurons in particular. It is now well established that the birth of these new neurons occurs in well-described sites: the hippocampus and the subventricular zone of the lateral ventricle, as well as in other brain regions including the hypothalamus. In this review, we describe the canonical neurogenic niches and illustrate the functional relevance of adult-born neurons of each neurogenic niche in the reproductive physiology. More specifically, we highlight the effect of reproductive social stimuli on the neurogenic processes and conversely, the contributions of adult-born neurons to the reproductive physiology and behavior. We next review the recent discovery of a novel neurogenic niche located in the hypothalamus and the median eminence and the compelling evidence of the link existing between the new-born hypothalamic neurons and the regulation of metabolism. In addition, new perspectives on the possible involvement of hypothalamic neurogenesis in the control of photoperiodic reproductive physiology in seasonal mammals are discussed. Altogether, the studies highlighted in this review demonstrate the potential role of neurogenesis in reproductive function and emphasize the importance of increasing our knowledge on the regulation processes and the physiological relevance of these adult-born neurons. This constitutes a necessary step toward a potential manipulation of these plasticity mechanisms. © 2016 Elsevier Inc.

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