Searchable, peer-reviewed, open-access proceedings from bioscience and biomedical conferences
Previous issue | Volume 5 | REDR2002 | Next issue

Reproduction in Domestic Ruminants V

Reproduction in Domestic Ruminants V

Neuroendocrine Interactions

bp0005rdr20 | Neuroendocrine Interactions | REDR2002

Stress and the control of LH secretion in the ewe

Smith RF , Ghuman SPS , Evans NP , Karsch FJ , Dobson H

Stress influences the activity of the reproductive system at several sites. One of the most significant effects is at level of the GnRH secretory system to reduce GnRH pulsatility and thus LH pulsatility. This in turn reduces the oestradiol signal that stimulates the GnRH–LH surge in the follicular phase. Three sequential phases have been identified in the induction of the GnRH–LH surge by oestradiol: (i) activation, (ii) transmission and (iii) surge secretion. There...

bp0005rdr21 | Neuroendocrine Interactions | REDR2002

Leptin actions on the reproductive neuroendocrine axis in sheep

Adam CL , Archer ZA , Miller DW

There is a growing literature on the role of leptin in appetite and neuroendocrine regulation in domestic ruminants. Circulating leptin concentration is higher in fat than in thin sheep, is reduced by chronic underfeeding and is higher in sheep subjected to long-day rather than short-day photoperiods. Leptin is reduced acutely by fasting and increases after meals so that there are long- and short-term components to the systemic leptin signal. Nutritional stimulation of reprodu...

bp0005rdr22 | Neuroendocrine Interactions | REDR2002

Sexually differentiated regulation of GnRH release by gonadal steroid hormones in sheep

Robinson JE , Birch RA , Grindrod JAE , Taylor JA , Unsworth WP

Exposure of Ihe sheep fetus to testosterone from day 30 to day 90 of a 147 day gestation causes the neurones that control GnRH secretion, the GnRH neuronal network, to become organized in a sex-specific manner. After androgen exposure in utero, GnRH neurones are activated in a sexually differentiated pattern by gonadal steroid hormones. Specifically, follicular phase concentrations of oestrogen trigger a GnRH 'surge' in ewes, but not in rams or females treated...

bp0005rdr23 | Neuroendocrine Interactions | REDR2002

Origin of cerebrospinal fluid melatonin and possible function in the integration of photoperiod

Tricoire H , Møller M , Chemineau P , Malpaux B

Melatonin, which is synthesized at night by the pineal gland, is present in the cerebrospinal fluid (CSF), but its entry site and its role in this compartment are not known. Using several approaches, we tested the hypothesis that melatonin enters the CSF through the pineal recess, an evagination of the third ventricle. CSF melatonin concentrations are higher near the pineal gland than in the anterior part of the third ventricle, and decrease markedly (80%) after sealing of...