Multiparametric MR Evaluation of the Photoperiodic Regulation of Hypothalamic Structures in Sheep.

Most organisms on earth, humans included, have developed strategies to cope with environmental day-night and seasonal cycles to survive. For most of them, their physiological and behavioral functions, including the reproductive function, are synchronized with the annual changes of day length, to ensure winter survival and subsequent reproductive success in the following spring. Sheep are sensitive to photoperiod, which also regulates natural adult neurogenesis in their hypothalamus.

Seasonal remodeling of the progenitor pool and its distribution in the ewe mediobasal hypothalamus.

Recent studies have reported the presence of adult neurogenesis in the arcuate nucleus periventricular space (pvARH) and in the median eminence (ME), two structures involved in reproductive function. In sheep, a seasonal mammal, decreasing daylight in autumn induces a higher neurogenic activity in these two structures. However, the different types of neural stem and progenitor cells (NSCs/NPCs) that populate the arcuate nucleus and median eminence, as well as their location, have not been evaluated.

Seasonal vascular plasticity in the mediobasal hypothalamus of the adult ewe.

Sheep, like most seasonal mammals, exhibit a cyclic adaptive reproductive physiology that allows ewes to give birth to their progeny during the spring when environmental conditions are favorable to their survival. This process relies on the detection of day length (or photoperiod) and is associated with profound changes in cellular plasticity and gene expression in the hypothalamic-pituitary-gonadal axis, mechanisms that are suggested to participate in the seasonal adaptation of neuroendocrine circuits. Recently, pituitary vascular growth has been proposed as a seasonally regulated process in which the vascular endothelial growth factor A (VEGFA), a well-known angiogenic cytokine, is suspected to play a crucial role.

Negative regulation of melatonin secretion by melatonin receptors in ovine pinealocytes.

Melatonin (MLT) is a biological modulator of circadian and seasonal rhythms and reproduction. The photoperiodic information is detected by retinal photoreceptors and transmitted through nerve transmissions to the pineal gland, where MLT is synthesized and secreted at night into the blood. MLT interacts with two G protein-coupled receptors, MT1 and MT2.

Blood oxygen level dependent fMRI and perfusion MRI in the sheep brain.

The ovine model could be an effective translational model but remains underexplored. Here, Blood Oxygen Level dependent functional MRI during visual stimulation and resting-state perfusion MRI were explored. We aimed at investigating the impact of isoflurane anesthesia during visual stimulation and evaluate resting cerebral blood flow and cerebral blood volume parameters in the lamb and adult sheep brain.

Chemerin impairs food intake and body weight in chicken: Focus on hypothalamic neuropeptides gene expression and AMPK signaling pathway.

Unlike mammals, the role of adipokines and more particularly of chemerin in the regulation of food intake is totally unknown in avian species. Here we investigated the effect of chemerin on the food and water consumption and on the body weight in chicken. We studied the effects on the plasma glucose and insulin concentrations and the hypothalamic neuropeptides and AMPK signaling pathway.

A high level of male sexual activity is necessary for the activation of the medial preoptic area and the arcuate nucleus during the 'male effect' in anestrous goats.

In small ungulates such as sheep or goats, the introduction of a male among a group of anovulatory females during the anestrus season leads to the reactivation of the gonadotrope axis and ovulation, a phenomenon known as the 'male effect'. In goats, our previous studies have demonstrated the importance of male sexual activity for an efficient reactivation of the gonadotrope axis assessed through ovulation and blood LH pulsatility. In the present experiment, we assessed whether the level of male sexual activity would also induce differential activation of two brain regions of key importance for the reactivation of GnRH activity, namely the medial preoptic area and the hypothalamic arcuate nucleus.