Behavioral and endocrine evaluation of the stressfulness of single-pen housing compared to group-housing and social isolation conditions.

Regulation of neuroendocrine responses is often studied in animals housed indoors in individual contiguous pens. In sheep, these housing conditions are used to control the environment, facilitate biological sampling and limit social stress. However, this type of housing also prevents exploratory behaviors and could induce stereotypies, non-compliant with welfare and possibly associated with a state of stress.

Morphofunctional interactions between galanin and GnRH-containing neurones in the diencephalon of the ewe. The effect of oestradiol.

In rodents, the neuropeptide galanin (Gal) is involved in controlling the release of gonadotrophin-releasing hormone (GnRH). In the female, this peptide is colocalized in a subpopulation of GnRH neurones and its expression is stimulated by oestradiol. In the ewe, the morphofunctional relationship between these two neuronal peptides is poorly understood.

Hypothalamic arcuate neuropeptide Y-neurons decrease periventricular somatostatin-neuronal activity before puberty in the female lamb: morphological arguments.

It is assumed that hypothalamic somatostatin plays a dominant role in the regulation of growth of developing lambs. On the other side, neuropeptide Y (NPY) neurons of the arcuate (ARC) nucleus are potentially involved in the control of gonadotrophins in prepubertal lambs and also of growth hormone (GH) secretion in adults. This study therefore investigated whether the transition from the prepubertal to the peripubertal period is accompanied by changes in NPY-ir and NPY mRNA content in neurons of the ARC nucleus and their putative projections to somatostatin neurons in both the ARC and periventricular (PEV) nuclei.

[Hypothalamic neuropeptides and control of GnRH neurones. Neuroanatomical study in the ewe].

Reproduction in mammals is directly controlled by GnRH neurons. These neurons are regulated by many external and internal factors, among which sexual steroids, in particular oestradiol, play an important part. However the mechanisms through which these steroids regulate GnRH secretion are largely unappreciated, and the neurochemical identity of central neurons liable to transmit the steroidal information to GnRH neurons is not completely clarified.

Access of dopamine to the median eminence and brain throughout local vascular pathways in sheep.

In female sheep, estradiol-dependent dopaminergic inhibition exerted by the A15 nucleus during long days (LD) results in a blockade of reproductive activity. This effect could involve the GnRH cell bodies or their terminals in the median eminence (ME). However, a vast majority of terminals of the A15 nucleus are located in neurohypophysis and only a few in the ME.