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Evaluation Of Dopaminergic And Antidopaminergic Agents For Use In Equine Metabolic Physiology, Nicole Arana Valencia
Evaluation Of Dopaminergic And Antidopaminergic Agents For Use In Equine Metabolic Physiology, Nicole Arana Valencia
LSU Doctoral Dissertations
A series of experiments studied the effects and practical applications of dopaminergic and antidopaminergic compounds in equine metabolic physiology. The first experiment was performed to assess the long-term effects of repeated cabergoline injections (every 10 days for a total of seven injections) on prolactin and α-melanocyte stimulating hormone concentrations in insulin insensitive mares. Additionally, the experiment also evaluated the use of cabergoline for improving insulin sensitivity. Plasma prolactin and α-melanocyte stimulating hormone concentrations were suppressed throughout the duration of the experiment even when the mares were challenged with a low-dose dopamine antagonist, sulpiride, the day previous to their subsequent cabergoline …
Characterization Of Equine Pulmonary Endothelin Receptors In Health And Disease, Sumanth Polikepahad
Characterization Of Equine Pulmonary Endothelin Receptors In Health And Disease, Sumanth Polikepahad
LSU Doctoral Dissertations
Endothelin-1 (ET-1) has been implicated in allergic type of respiratory inflammatory diseases in various species of animals including horses. This peptide elicits its actions by acting through endothelin-A (ET-A) and endothelin-B (ET-B) receptor sub-types. In this project, we have hypothesized that endothelin receptors (both ET-A and ET-B) are altered in terms of affinity and expression, in the lungs of summer pasture-associated obstructive pulmonary disease (SPAOPD)-affected horses. Objective of this dissertation was to determine the alterations in the affinity and expression of endothelin receptors in the lungs of healthy and SPAOPD-affected horses. To pursue our hypothesis, we have employed pharmacological, immunohistochemical …
Role Of Endothelin-1 In The Gastrointestinal Tract Of Horses In Health And Disease, Ramaswamy Monickarasi Chidambaram
Role Of Endothelin-1 In The Gastrointestinal Tract Of Horses In Health And Disease, Ramaswamy Monickarasi Chidambaram
LSU Doctoral Dissertations
Gastrointestinal tract disease is the leading natural cause of death in horses and horses with ischemic intestinal disease have the greatest mortality. We hypothesized there is basal synthesis of endothelin-1 (ET-1) in the intestinal tract of healthy horses that is likely involved in regulating vasomotor tone, secretion and motility and that ET-1 synthesis increases with gastrointestinal tract disease, which may be involved in the pathophysiology of these disorders. Plasma ET-like immunoreactivity was increased in horses with naturally-acquired gastrointestinal disease, compared with normal horses; values were greatest in horses with large intestinal strangulation obstruction, enterocolitis and peritonitis. There was an association …
Role Of Endothelin In The Pathogenesis Of Acute Laminitis In Horses, Ashley Michelle Stokes
Role Of Endothelin In The Pathogenesis Of Acute Laminitis In Horses, Ashley Michelle Stokes
LSU Doctoral Dissertations
Acute laminitis is a severely debilitating disease of the laminae of the equine digit; however, the mechanism(s) of pathogenesis have yet to be fully elucidated. In physiologic states, the endothelium synthesizes substances, such as nitric oxide (NO; vasodilator) and endothelin-1 (ET-1; profound vasoconstrictor), which play a crucial role in vasomotor regulation. The overall hypothesis is that the initiating factor in the onset of acute laminitis is a disruption in the balance between NO and ET-1, which leads to digital vasoconstriction and subsequent laminar ischemic necrosis. In vitro studies with digital vessels from healthy horses and horses with naturally-acquired laminitis determined …
Endocrine And Reproductive Responses To Implants Of Deslorein Acetate In Horses, Carrie Ann Johnson
Endocrine And Reproductive Responses To Implants Of Deslorein Acetate In Horses, Carrie Ann Johnson
LSU Doctoral Dissertations
Four experiments were performed to study the effects of the gonadotropin releasing hormone (GnRH) analog, deslorelin acetate (Ovuplant™), on endocrine and reproductive characteristics in mares. The first experiment tested whether anecdotal field reports of Ovuplant causing extended interovulatory intervals would be detectable under controlled, experimental conditions. The use of Ovuplant to hasten ovulation in 13 mares, compared to 12 controls, increased (P < 0.05) the interovulatory interval by 6.2 d and suppressed (P < 0.05) plasma concentrations of both luteinizing hormone (LH) and follicle stimulating hormone (FSH) for approximately 11 d. Two mares receiving Ovuplant did not return to estrus within 30 d. In the second experiment, 10 control mares and 10 mares induced to ovulate with Ovuplant were administered GnRH (50 μg) on d 1, 4, 7, and 10 after ovulation. Again, treated mares had a longer (4.4 d, P < 0.05) interovulatory interval and suppressed LH and FSH concentrations in daily plasma samples. The gonadotropin response to GnRH was lower (P < 0.05) in the deslorelin mares on d 1, 4, and 7, indicating a lack of pituitary responsiveness. In the third experiment, 9 stallions and 12 steroid-treated geldings were used to determine if males were potential models for studying the deslorelin-induced gonadotropin suppression. In both cases, treatment with Ovuplant caused an initial rise in both gonadotropins followed by suppression for about 14 d. In the last experiment, 21 mares were used to determine if multiple doses of deslorelin would cause complete ovarian shutdown. Mares received either sham injections, three Ovuplant implants on the first day, or one implant per day for 3 d (n = 7 per group). Treatment with multiple deslorelin implants increased (P < 0.05) the interovulatory interval by 14.8 d and suppressed LH and FSH concentrations for approximately 25 d, however no mares exhibited complete ovarian shutdown. In conclusion, deslorelin acetate implants in horses in the form of Ovuplant induce short-term increases in LH and FSH secretion followed by long-term suppression of these concentrations and an insensitivity of the pituitary to GnRH. In a small percentage of mares, long-term ovarian shutdown is a possibility.