Dose-Response of Prolactin to Increasing Doses of the Dopamine Receptor Antagonist, Sulpiride, in Horses: Effect of Season in Mares and Stallions of Estradiol Pretreatment in Geldings

Clavier, Sarah; Thompson, Donald L.; Caltabilota, T.J.; Mitcham, P.B.

doi:10.1016/j.jevs.2011.09.066

Cited by 14 publications

(6 citation statements)

References 28 publications

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“…Not only did MSH concentrations increase after sulpiride injection in the present experiment, but the response was greater than the response to the standard TRH dose used in previous trials (0.002 mg/kg, or 1 mg for a 500 kg horse). The dose of sulpiride used herein (0.01 mg/kg, or 5 mg of the racemic mixture for a 500 kg horse) was calculated to be approximately 50% of that dose producing maximal prolactin response in mares in March, as described by Clavier et al (2012). For comparison, we have reported previously that the prolactin and TSH responses to TRH were similar for doses of 0.4, 2, and 10 mg ; thus the approximate 1-mg dose used herein could be considered saturating.…”

Section: Chapter IV Discussionmentioning

confidence: 99%

Changes in plasma melanocyte-stimulating hormone, ACTH, prolactin, GH, LH, FSH, and thyroid-stimulating hormone in response to injection of sulpiride, thyrotropin-releasing hormone, or vehicle in insulin-sensitive and -insensitive mares

Valencia¹,

Thompson²,

Mitcham³

2013

Domestic Animal Endocrinology

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Six insulin-sensitive and 6 insulin-insensitive mares were used in a replicated 3 by 3 Latin square design to determine the pituitary hormonal responses (compared with vehicle) to sulpiride and thyrotropin-releasing hormone (TRH), 2 compounds commonly used to diagnose pituitary pars intermedia dysfunction (PPID) in horses. Mares were classified as insulin sensitive or insensitive by their previous glucose responses to direct injection of human recombinant insulin. Treatment days were February 25, 2012, and March 10 and 24, 2012. Treatments were sulpiride (racemic mixture, 0.01 mg/kg BW), TRH (0.002 mg/kg BW), and vehicle (saline, 0.01 mL/kg BW) administered intravenously. Blood samples were collected via jugular catheters at -10, 0, 5, 10, 20, 30, 45, 60, 90, and 120 min relative to treatment injection. Plasma ACTH concentrations were variable and were not affected by treatment or insulin sensitivity category. Plasma melanocyte-stimulating hormone (MSH) concentrations responded (P < 0.01) to both sulpiride and TRH injection and were greater (P < 0.05) in insulin-insensitive mares than in sensitive mares. Plasma prolactin concentrations responded (P < 0.01) to both sulpiride and TRH injection, and the response was greater (P < 0.05) for sulpiride; no effect of insulin sensitivity was observed. Plasma thyroid-stimulating hormone (TSH) concentrations responded (P < 0.01) to TRH injection only and were higher (P < 0.05) in insulin-sensitive mares in almost all time periods. Plasma LH and FSH concentrations varied with time (P < 0.05), particularly in the first week of the experiment, but were not affected by treatment or insulin sensitivity category. Plasma GH concentrations were affected (P < 0.05) only by day of treatment. The greater MSH responses to sulpiride and TRH in insulin-insensitive mares were similar to, but not as exaggerated as, those observed by others for PPID horses. In addition, the reduced TSH concentrations in insulin-insensitive mares are consistent with our previous observation of elevated plasma triiodothyronine concentrations in hyperleptinemic horses (later shown to be insulin insensitive as well).

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Section: Chapter IV Discussionmentioning

confidence: 99%

Changes in plasma melanocyte-stimulating hormone, ACTH, prolactin, GH, LH, FSH, and thyroid-stimulating hormone in response to injection of sulpiride, thyrotropin-releasing hormone, or vehicle in insulin-sensitive and -insensitive mares

Valencia¹,

Thompson²,

Mitcham³

2013

Domestic Animal Endocrinology

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“…How estradiol stimulates prolactin production by the equine pituitary was a question raised by Clavier et al [77]. Prolactin responses to increasing doses of sulpiride in vehicle-treated geldings and in geldings treated with 100 mg of ECP were used to generate dose-response curves from which the effective dose-50 (dose at which 50% of maximal response is achieved) could be derived.…”

Section: Estrogen Effectsmentioning

confidence: 99%

Prolactin in the Horse: Historical Perspective, Actions and Reactions, and Its Role in Reproduction

Thompson

Oberhaus

2015

Journal of Equine Veterinary Science

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“…Several experiments since that first report have confirmed the stimulatory effect of estradiol on prolactin production and secretion in horses [3][4][5], and application of the results from those experiments led to the development of a estradiol cypionate-sulpiride (or domperidone) combination treatment for inducing follicular growth and ovulation in seasonally anovulatory mares in winter [6,7]. The stimulation of prolactin via the estradiol-dopaminergic antagonist combination is synergistic (reviewed by [8]) and is dependent on both factors being present at the same time; interestingly, other prolactin secretagogues, such as exercise or thyrotropin releasing hormone (TRH), do not synergize with estradiol pretreatment [5].…”

Section: Introductionmentioning

confidence: 82%

“…Not until Kelley et al [3] combined estradiol pretreatment with subsequent administration of the dopamine antagonist, sulpiride, was it known how the two treatments synergized to produce large increases in not only pituitary content but also day-to-day secretion of prolactin. Since that original report [3], the synergistic effect of estradiol coupled with a dopamine antagonist (either sulpiride or domperidone) on prolactin secretion has been shown multiple times [4][5][6][7]. Interestingly, other secretory stimuli for prolactin (exercise, PGF 2a administration, TRH administration) do not synergize with estradiol treatment in the same manner [5], indicating that those stimuli must act on lactotropes via a different mechanism than dopaminergic antagonists.…”

Section: Discussionmentioning

confidence: 99%

Effects of Estradiol-17β or Dihydrotestosterone on Cell Types in Equine Pituitaries Staining for Prolactin, Growth Hormone, or Both

Rahmanian

Thompson

2016

Journal of Equine Veterinary Science

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a b s t r a c tOvariectomized pony mares were treated with vehicle (controls), estradiol-17b (estradiol), or dihydrotestosterone (DHT) daily for 21 days in summer, and the pituitary content of prolactin and growth hormone (GH) and the numbers of cells staining immunocytochemically for prolactin (lactotropes), GH (somatotropes), or both hormones (mammosomatotropes) were assessed. Treatments did not alter (P > .1) plasma prolactin concentrations over the 21 days. Estradiol treatment increased (P < .05) the pituitary content of prolactin several-fold relative to controls and DHT-treated ponies. The number of lactotropes was also increased (P <.05), as was the number of mammosomatotropes (P < .05). Treatment with DHT did not alter (P > .1) any prolactin characteristic. The number of somatotropes was not altered by either treatment (P > .1) nor was the pituitary content of GH (P > .1). Given that the mass of prolactin accumulation in the pituitary in response to estradiol was several-fold greater than the approximate doubling of the number of lactotropes and mammosomatotropes, it appears that estradiol administration to ovariectomized pony mares stimulates not only the number of prolactin-producing cells but also the amount of prolactin production per cell.

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Dose-Response of Prolactin to Increasing Doses of the Dopamine Receptor Antagonist, Sulpiride, in Horses: Effect of Season in Mares and Stallions of Estradiol Pretreatment in Geldings

Cited by 14 publications

References 28 publications

Changes in plasma melanocyte-stimulating hormone, ACTH, prolactin, GH, LH, FSH, and thyroid-stimulating hormone in response to injection of sulpiride, thyrotropin-releasing hormone, or vehicle in insulin-sensitive and -insensitive mares

Changes in plasma melanocyte-stimulating hormone, ACTH, prolactin, GH, LH, FSH, and thyroid-stimulating hormone in response to injection of sulpiride, thyrotropin-releasing hormone, or vehicle in insulin-sensitive and -insensitive mares

Prolactin in the Horse: Historical Perspective, Actions and Reactions, and Its Role in Reproduction

Effects of Estradiol-17β or Dihydrotestosterone on Cell Types in Equine Pituitaries Staining for Prolactin, Growth Hormone, or Both

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