1a.Objectives (from AD-416):
1. Determine the mechanism through which secretion of luteinizing hormone is suppressed in the prepubertal gilt.
2. Determine the mechanism of inhibition of luteinizing hormone release directly from the anterior pituitary gland of the gilt.
3. Determine the mechanism through which nutrition regulates gonadotropic output of the hypothalamic-pituitary axis of the gilt.
1b.Approach (from AD-416):
On average, 20% of gilts fail to reach puberty and become pregnant. Lack of sufficient secretion of gonadotropin hormones (e.g. luteinizing hormone; LH) from the pituitary gland is a prominent reason for delayed puberty of pigs. Mechanisms in the hypothalamus that control LH secretion in the gilt are not well understood, but nutrition is an important component. The project goal is to minimize reproductive failure of replacement gilts. The objectives will be to establish the function of RFamide-related and kisspeptin peptides in the control of LH secretion of the pig and identify their role in integrating nutrition with the gonadotropic axis of the gilt. Our approach, using intracerebroventricular cannulation, will be to establish the central effects of RFamide-related peptides on secretion of LH in gilts (Aim I). We will determine the direct effect of RFamide-related peptides on LH release from the pituitary gland of the pig (Aim II), and identify the relationship between energy balance and kisspeptin neurons in the hypothalamus of the gilt (Aim III). The rationale is that this work will advance our understanding of the basic biological mechanisms that control gonadotropin secretion in the gilt. The proposed research is significant, therefore, because application of this new fundamental knowledge is expected to lead to development of new strategies to minimize reproductive failure and maximize fertility of replacement gilts. This in turn will increase reproductive efficiency and decrease the expense of pork production.
Hypothalamic tissue has been collected from gilts and will be sectioned and sent to Washington State University. To meet Specific Objective 3, ovariectomized gilts will be placed on nutritional diets at Clay Center, Nebraska, in August or September. Blood samples will be collected and analyzed at Clay Center, Nebraska, to quantify hormonal differences. Hypothalami will be collected and sent to Washington State University to quantify expression of RFamide-related peptide and Kisspeptin in the brain.