Localization and quantification of melatonin receptors in the diencephalon and posterior telencephalon of the sheep brain.

In an attempt to better understand the mechanisms by which melatonin controls neuroendocrine activity, we tried to define with accuracy the brain areas where the density of melatonin receptors is the highest in sheep and to establish their characteristics. The specific labelling of 125I-melatonin was first revealed by autoradiography on brain sections of the posterior telencephalon and diencephalon in three ewes. The extent and position of the five structures where the binding was found to be the highest (i.

Primary cell culture of LHRH neurones from embryonic olfactory placode in the sheep (Ovis aries).

The aim of this study was to establish an in vitro model of ovine luteinizing hormone-releasing hormone (LHRH) neurones. Olfactory placodes from 26 day-old sheep embryos (E26) were used for explant culture. Cultures were maintained successfully up to 35 days, but were usually used at 17 days for immunocytochemistry.

Relationship between the number of immunostaining gonadotropes and the plasma concentrations of gonadotrophins in ewes with and without the FecBB gene.

Booroola ewes possess a major gene, FecBB, that influences their ovulation rate (number of ovulations per oestrous cycle). Homozygous (BB) carriers of the FecBB gene have higher plasma concentrations of FSH and sometimes LH relative to the non-carriers (++). The aim of this study was to determine whether the plasma concentration differences in FSH or LH between the genotypes were due to a greater number of FSH beta- or LH beta-immunostaining cells in the anterior pituitary gland of BB ewes during the luteal phase of the oestrous cycle.

Bilateral lesions of the suprachiasmatic nuclei alter the nocturnal melatonin secretion in sheep.

The hypothalamic suprachiasmatic nuclei (SCN) constitute both the biological clock of many circadian rhythms, and the first relay in the transmission of light cues from the retina to the pineal gland, which releases, via nocturnal melatonin secretion, an endocrine expression of the daylength. The aim of the present work was to investigate the precise role of the SCN in the entrainment of the nocturnal rhythm of melatonin (MEL) in sheep. Bilateral lesions of the SCN were performed via a transsinusal surgical approach in 10 adult rams submitted to a constant photoperiod (16:8D).