Dopamine is a neurotransmitter present in the central nervous system of horses, involved in regulating various physiological and behavioral processes. It plays a role in movement, mood, and reward mechanisms, influencing how horses respond to stimuli and interact with their environment. Dopamine pathways in horses are similar to those in other mammals and are integral to neural communication and function. Research on dopamine in horses explores its effects on behavior, training responses, and its potential involvement in neurological disorders. This page compiles peer-reviewed research studies and scholarly articles that examine the role, regulation, and implications of dopamine in equine neurobiology and behavior.
Galinelli NC, Bamford NJ, de Laat MA, Sillence MN, Harris PA, Bailey SR.Insulin dysregulation in horses is characterised by hyperinsulinaemia and/or tissue insulin resistance and is associated with increased risk of laminitis. There is growing evidence in other species that dopamine attenuates insulin release from the pancreas; however, this has yet to be examined in horses. The present study aimed to identify whether there are cells capable of producing or responding to dopamine within the equine gastrointestinal mucosa and pancreas. Tissue samples were collected from the stomach, small and large intestines, and pancreas of six mature horses following euthanasia....
Kim J, Jung H, Yoon M.Dopamine (DA) is a neurotransmitter associated with animal behaviors. Along with other neurotransmitters such as oxytocin (OXT) and serotonin (5-HT), DA is also involved in determining the temperament of animals. However, the involvement of DA in horse temperament has not been well elucidated. Therefore, in this study, we aimed to determine the correlation between plasma DA concentration and OXT and 5-HT concentrations and behavioral temperament (eg, docility and friendliness, fearfulness, dominance, and trainability) of horses. Blood samples were collected from 31 horses and the concentration...
Keen B, Cawley A, Reedy B, Noble G, Loy J, Fu S.The use of catechol-O-methyltransferase inhibitors may mask doping agents, primarily levodopa, administered to racehorses and prolong the stimulating effects of dopaminergic compounds such as dopamine. It is known that 3-methoxytyramine is a metabolite of dopamine and 3-methoxytyrosine is a metabolite of levodopa thus these compounds are proposed to be potential biomarkers of interest. Previous research established a urinary threshold of 4,000 ng/mL for 3-methoxytyramine to monitor misuse of dopaminergic agents. However, there is no equivalent biomarker in plasma. To address this deficiency a...
Huang L, Palmieri C, Bertin FR.Pituitary pars intermedia dysfunction (PPID) is an endocrinopathy commonly affecting old horses. It is a spontaneously occurring, progressive disease that is still poorly understood. Previous studies have observed neurodegeneration of the dopaminergic inhibition of melanotrophs, which leads to decreased dopamine (DA) in the pars intermedia (PI) and increased pro-opiomelanocortin-derived peptides circulating in plasma. However, rats knockout for the dopamine D2 receptor (D2r) similarly develop PI hypertrophy and hyperplasia. Thus, based on the current pathophysiological theory of PPID, whether ...
Kim J, Jung H, Choi JY, Lee JW, Yoon M.Dopamine (DA) is known to be a key modulator of animal behaviors. Thus, the plasma concentration of DA might be used as a biomarker for the behavioral characteristics of horses. The behavioral characteristics of horses vary depending on the breed, age, and sex. Moreover, the DA receptor genotypes are also related to horse behaviors. Thus, the aim of this study was to investigate the DA concentration variations of horse plasma by breed, age, sex, or genotype of its receptor. The horses were divided by breed into Thoroughbred (n = 13), Pony (n = 9), Warmblood (n = 4), and Haflinger (n = 5). The ...
McBride SD, Roberts K, Hemmings AJ, Ninomiya S, Parker MO.Stress and genotype elicit changes in impulse control in a range of species that are attributable to adaptations in both the central and peripheral nervous system. We examined aspects of this mechanism in the horse by assessing the effect of a dopamine receptor genotype (DRD4) and central dopaminergic tone (measured via spontaneous blink rate [SBR] and behavioral initiation rate [BIR]), on measures of impulsivity, compulsivity (3-choice serial reaction time task) and sympathetic/ parasympathetic system balance (heart rate variability [HRV]). Genotype did not have a significant effect on any of...
Gehlen H, Fisch J, Merle R, Trachsel DS.Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses. Objective: To determine whether pergolide induces valvular disease in horses or affects the cardiac function. Methods: Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in hor...
Bantle CM, Rocha SM, French CT, Phillips AT, Tran K, Olson KE, Bass TA, Aboellail T, Smeyne RJ, Tjalkens RB.Viral infection of the central nervous system (CNS) can cause lasting neurological decline in surviving patients and can present with symptoms resembling Parkinson's disease (PD). The mechanisms underlying postencephalitic parkinsonism remain unclear but are thought to involve increased innate inflammatory signaling in glial cells, resulting in persistent neuroinflammation. We therefore studied the role of glial cells in regulating neuropathology in postencephalitic parkinsonism by studying the involvement of astrocytes in loss of dopaminergic neurons and aggregation of α-synuclein protein fo...
Matsuda H, Matsuda K, Muko R, Oikawa MA, Tanaka A.Much is known regarding a good prognosis of acute kidney injury (AKI) is achieved with adequate, intensive, and early treatment, which leads to acceleration of the renal blood flow rate and associated urination. Low-dose dopamine (1 to 5 μg/kg bwt per min) is a treatment option for AKI in humans but remains controversial for use in horses because of the lack of extensive clinical trial data. A 19-year-old Westfalen horse gelding was referred to the Animal Medical Center with a 1-hour history of mild abdominal pain and anorexia after dressage exercise for 1 hour. Since elevated serum levels o...
Arfuso F, Giannetto C, Giudice E, Fazio F, Panzera M, Piccione G.The current study aimed to investigate whether peripheral modulators of serotoninergic function and neurohumoral factors' changes in athletic horses during an official jumping competition, and to evaluate their relationship with the physical performance of competing horses. From 7 Italian Saddle mares (6-9 years; mean body weight 440 ± 15 kg), performing the same standardized warm-up and jumping course during an official class, heart rate (HR) was monitored throughout the competition. Rectal temperature (RT) measurement, blood lactate and glucose concentration, serum tryptophan, leucine, vali...
Banse HE, Whitehead AE, McFarlane D, Chelikani PK.Pituitary pars intermedia dysfunction (PPID) is a common endocrine disorder of aged horses, with muscle atrophy as one of the clinical signs. We sought to compare muscle mass and regulation of skeletal muscle proteolysis between horses with PPID and muscle atrophy to older horses without PPID, and to assess the impact of treatment with pergolide (dopaminergic agonist) on PPID horses. We hypothesized that PPID-associated muscle atrophy is a result of increased proteolysis, and that markers of muscle atrophy and proteolysis would improve over time with pergolide treatment. Markers of muscle atro...
Tatum RC, McGowan CM, Ireland JL.Pergolide, a dopamine agonist, is commonly administered to manage pituitary pars intermedia dysfunction (PPID), a progressive neurodegenerative disease prevalent in aged horses. However, available evidence regarding pergolide's efficacy in improving clinical and endocrine parameters is limited. The aim of this systematic review was to assess published literature and evaluate evidence regarding whether pergolide treatment results in improvement of clinical signs and/or adrenocorticotrophic hormone (ACTH) concentration compared to no treatment or other unlicensed treatments. Systematic searches ...
Fortin JS, Benskey MJ, Lookingland KJ, Patterson JS, Howey EB, Goudreau JL, Schott HC.Pituitary pars intermedia dysfunction (PPID) develops slowly in aged horses as degeneration of hypothalamic dopaminergic neurons leads to proliferation of pars intermedia (PI) melanotropes through hyperplasia and adenoma formation. Dopamine (DA) concentrations and tyrosine hydroxylase (TH) immunoreactivity are markedly reduced in PI tissue of PPID-affected equids and treatment with the DA receptor agonist pergolide results in notable clinical improvement. Thus, we hypothesized that pergolide treatment of PPID-affected horses would result in greater DA and TH levels in PI tissue collected from ...
Schwarz B, Ihry P.A 26-year-old pony mare (ca. 180 kg bodyweight) was presented as an emergency because it had erroneously received 110 times its standard dose of pergolide (Prascend) per os approximately 4 hours earlier. Clinical examination initially was normal except tachycardia of 52 beats/min. The pony was treated symptomatically with paraffin oil and activated charcoal per nasogastric tube to prevent further systemic absorption and accelerate intestinal excretion of the pergolide. Furthermore, the pony received 400 mg of dopamine antagonist azaperone (Stresnil) intramuscularly (i.m.) followed by 80 mg...
Briefer Freymond S, Bardou D, Beuret S, Bachmann I, Zuberbühler K, Briefer EF.Although stereotypic behaviors are a common problem in captive animals, why certain individuals are more prone to develop them remains elusive. In horses, individuals show considerable differences in how they perceive and react to external events, suggesting that this may partially account for the emergence of stereotypies in this species. In this study, we focused on crib-biting, the most common stereotypy displayed by horses. We compared how established crib-biters ("CB" = 19) and normal controls ("C" = 18) differed in response to a standard "personality" assessment test battery, i.e., react...
Bowden GD, Land KM, O'Connor RM, Fritz HM.The apicomplexan parasite Sarcocystis neurona is the primary etiologic agent of equine protozoal myeloencephalitis (EPM), a serious neurologic disease of horses. Many horses in the U.S. are at risk of developing EPM; approximately 50% of all horses in the U.S. have been exposed to S. neurona and treatments for EPM are 60-70% effective. Advancement of treatment requires new technology to identify new drugs for EPM. To address this critical need, we developed, validated, and implemented a high-throughput screen to test 725 FDA-approved compounds from the NIH clinical collections library for anti...
Catecholamines are among the most frequently investigated parameters for studying sympathoadrenal activity in response to stress conditions. Objective: To evaluate basal plasma concentrations of catecholamines (adrenaline, noradrenaline and dopamine) in healthy donkeys. Methods: Cross-sectional study. Methods: Catecholamine concentrations from 440 Martina Franca donkeys were determined: 269 females and 171 entire males, aged from 4 months to 24 years. Animals were subdivided into four age categories: under 12 months old (64 males and 54 females), from 13 to 36 months (56 males and 75 females),...
Medica P, Bruschetta G, Cravana C, Ferlazzo A, Fazio E.The objective of current study was to evaluate the effect of transportation stress on the circulating adrenaline (A), noradrenaline (NA) and dopamine (DA) responses of stallions, according to the different distances. Forty-two stallions were studied before and after road transportation of 100, 200 and 300km, for a period of 1-3h. An increase in plasma A after 100km (P<0.001) was observed. A similar result was seen in plasma NA after 100km (P<0.001), and 300km (P<0.001). Increases in plasma DA after 100 and 200km (P<0.0001) were observed, with a decrease after 300km (P<0.0001). S...
Hopster K, Ambrisko TD, Kästner SBR.To compare the lithium dilution method for cardiac output (LiDCO) and bolus-thermo-dilution (BTD) measurements before and during infusion of dobutamine, dopamine, phenylephrine, or noradrenaline at 2 different doses in anesthetized horses and to examine the correlation between sensor voltages (saline-blood exposed) and possible measurement errors. Methods: Prospective experimental study. Methods: University teaching hospital. Methods: Nine Warmblood horses. Methods: Following 90 minutes of equilibration, 3 different doses of dobutamine (0.5-3 μg/kg/min), dopamine (1-5 μg/kg/min), phenylephri...
Wang N, Zhang D, Deng X, Sun Y, Wang X, Ma P, Song D.Herein we report a novel polydopamine-silver nanoparticle-polydopamine-gold (PDA-AgNPs-PDA-Au) film based surface plasmon resonance (SPR) biosensor for horse IgG detection. The PDA-AgNPs-PDA-Au film sensing platform was built on Au-film via layer-by-layer self-assembly. Ag ion was reduced in situ to AgNPs in presence of PDA. The top PDA layer can prevent AgNPs from being oxidized and connect with antibody via Schiff alkali reaction directly. The morphology and thickness of the modified gold film were characterized using scanning electron microscope and Talystep. Experimental results show that ...
Dancker C, Hopster K, Rohn K, Kästner SB.In the horse, effects of cardiovascular-active drugs on local perfusion of the gastrointestinal tract are poorly understood. Objective: To determine the effect of drugs commonly used to support blood pressure, on local intestinal blood flow and tissue oxygenation under isoflurane anaesthesia. Methods: In vivo randomised crossover experiment. Methods: Ten horses were anaesthetised with isoflurane. After 90 min of equilibration three doses (μg/kg bwt/min) of dobutamine (DOB 0.5/1/3), dopamine (DA 1/2/5), noradrenaline (NA 0.1/0.2/0.5) and phenylephrine (PHE 0.5/1/3) were infused for 15 min, in ...
Durham AE.Equine endocrine disease is commonly encountered by equine practitioners. Pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS) predominate. The most logical therapeutic approach in PPID uses dopamine agonists; pergolide mesylate is the most common. Bromocryptine and cabergoline are alternative drugs with similar actions. Drugs from other classes have a poor evidence basis, although cyproheptadine and trilostane might be considered. EMS requires management changes as the primary approach; reasonable justification for use of drugs such as levothyroxine and metformin m...
Marcilla M, Muñoz A, Satué K.Systemic physiological changes required for placental and fetal development during pregnancy are associated with an activation of the sympathetic nervous system (SNS) and the hypothalamus-pituitary-adrenal axis (HPA) in women, but this fact has not been investigated in mares. Venous blood samples were taken monthly from 31 successful Spanish mares during the 11months of pregnancy. During the first 4months of pregnancy, adrenaline (AD), dopamine (DOPA) and ACTH increases, whereas 5-hydroxitryptamine (5-HT) decreased, and noradrenaline (NAD) and cortisol (CORT) did not change. Serum NAD increase...
Roberts K, Hemmings AJ, Moore-Colyer M, Parker MO, McBride SD.A relationship between dopamine and temperament has previously been described in human cases of dopaminergic dysfunction. Adjustment in temperament prior to disease manifestation can enable the early identification of individuals at risk of such conditions, and scope exists to extend this application of temperament alterations to cases of dopaminergic dysfunction in horses. A multivariate and mixed-methods approach utilising a questionnaire along with two inferred measurements of dopamine activity (Spontaneous Blink Rate [SBR] and behavioral initiation rate [BIR]) were recorded from direct obs...
Zoller D, Lüttgenau J, Steffen S, Bollwein H.Poor uterine perfusion has been proposed as a cause of infertility in mares. The objective of this study was to investigate the effect of isosorbide dinitrate (ISDN), a nitric oxide donor, on uterine and ovarian blood flow resistance during diestrus and early pregnancy in mares. Six Trotter mares, aged 7 to 14 years, were examined daily during the first 11 days of three diestrous periods, and five of those mares were also examined during the first 11 days of two pregnancies. Six mares randomly received a placebo, a low dose (30 mg, ISDN30), or a high dose of ISDN (60 mg, ISDN60) through t...
McGorum BC, Pirie RS, Eaton SL, Keen JA, Cumyn EM, Arnott DM, Chen W, Lamont DJ, Graham LC, Llavero Hurtado M, Pemberton A, Wishart TM.Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of ∼2%. An apparently identical disease occurs in multiple species, including but not limited to cats, dogs, and rabbits. Although the precise etiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here, we use a bottom-up approach be...
Spelta CW.Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally do...
Urra JA, Villaroel-Espíndola F, Covarrubias AA, Rodríguez-Gil JE, Ramírez-Reveco A, Concha II.Dopamine is a catecholamine with multiple physiological functions, playing a key role in nervous system; however its participation in reproductive processes and sperm physiology is controversial. High dopamine concentrations have been reported in different portions of the feminine and masculine reproductive tract, although the role fulfilled by this catecholamine in reproductive physiology is as yet unknown. We have previously shown that dopamine type 2 receptor is functional in boar sperm, suggesting that dopamine acts as a physiological modulator of sperm viability, capacitation and motility...
Doran G, Hughes K, Rendle D, Edwards S.Pergolide is used to treat pituitary pars intermedia dysfunction (equine Cushing's Disease), a neurodegenerative condition associated with loss of dopaminergic inhibition of the pituitary in horses. After oral administration, only low concentrations of the drug are achieved in plasma, making drug detection and quantification difficult. While direct analysis of plasma using sensitive MS/MS techniques is possible, dirty plasma samples and mobile phase buffers can cause instrumentation to become rapidly incapacitated. A method using LC with fluorescence detection was developed for pergolide analy...
Jacobson GA, Pirie A, Edwards S, Hughes KJ, Rendle DI, Davies NW.Pergolide, an ergot-derived dopamine D2 receptor agonist, is used extensively as an orally administered treatment for pituitary pars intermedia dysfunction (PPID) in horses. One of the barriers associated with pergolide determinations in plasma for pharmacokinetic applications has been the technically demanding requirement for sensitivity. The objective of our work was to develop a simple assay for the determination of pergolide in plasma and demonstrate its potential application in the study of pergolide pharmacokinetics (PK) in horses. A UPLC-MS/MS assay was developed with a simple sample pr...
Fornstedt B, Rosengren E, Carlsson A.The 5-S-cysteinyl derivatives of dopamine, dopa (3,4-dihydroxyphenylalanine) and dopac (3,4-dihydroxyphenylacetic acid) were synthesized and used as reference compounds in high performance liquid chromatography analyses of extracts from various brain regions of eight mammalian species. All three metabolites were detected in the brains of all the species studied. The regional distribution of the metabolites was similar to that of dopamine; the metabolite concentrations ranged from less than 0.1 percent to more than 1 percent of the dopamine level, the highest ratios generally being found in sub...
McFarlane D, Dybdal N, Donaldson MT, Miller L, Cribb AE.Equine pituitary pars intermedia dysfunction (PPID) is a spontaneously occurring progressive disease affecting aged horses and ponies. The pathogenesis of PPID is poorly understood, but the available evidence supports a loss of dopaminergic inhibition of the melanotropes of the pars intermedia. Horses with PPID have increased plasma concentrations of pars intermedia pro-opiomelanocortin-derived peptides that decrease in response to dopamine or dopamine agonist administration. Dopamine and dopamine metabolite concentrations are decreased in the pars intermedia of affected horses compared to age...
Momozawa Y, Takeuchi Y, Kusunose R, Kikusui T, Mori Y.The variable number of tandem repeats (VNTR) polymorphism of the dopamine D4 receptor (DRD4) gene has been reported to be associated with the personality trait of novelty-seeking in humans. In the genus Equus, this region includes an 18-bp repeat unit and there are inter- and intraspecies differences in the number of repetitions. Because horses are unique among livestock species in that their temperament is considered important, we investigated the possible role of this region on equine temperament in thoroughbred horses. We simultaneously determined the sequences of this polymorphic region an...
Pozor MA, McDonnell SM.The objectives of this study were to evaluate the potential use of color Doppler ultrasound to characterize blood flow to the stallion testis, and to establish reference values for Doppler measures of blood flow in the testicular artery of the stallion. Both testes from each of 52 horses were examined using a pulsed-wave color Doppler ultrasound with a sector array 5/7.5 MHz transducer with a 1mm gate setting. Peak systolic velocity (PSV), end diastolic velocity (EDV), resistive index (RI), and pulsatility index (PI) of the testicular artery were measured in each of two locations, the convolut...
McFarlane D.Parkinson's disease (PD) is a leading cause of neurologic disability in the aged population. Remarkable progress has been made in the past decade to understand the cellular and molecular events that occur in PD. However attempts to unravel the early, initiating factors in the pathogenesis of dopaminergic neurodegeneration and PD have been limited by the lack of a suitable animal model. Models in which there has been genetic or environmental manipulation are not of use in determining the natural cause of a disease. While a large scale prospective human study would be ideal, the relatively low p...
Dancker C, Hopster K, Rohn K, Kästner SB.In the horse, effects of cardiovascular-active drugs on local perfusion of the gastrointestinal tract are poorly understood. Objective: To determine the effect of drugs commonly used to support blood pressure, on local intestinal blood flow and tissue oxygenation under isoflurane anaesthesia. Methods: In vivo randomised crossover experiment. Methods: Ten horses were anaesthetised with isoflurane. After 90 min of equilibration three doses (μg/kg bwt/min) of dobutamine (DOB 0.5/1/3), dopamine (DA 1/2/5), noradrenaline (NA 0.1/0.2/0.5) and phenylephrine (PHE 0.5/1/3) were infused for 15 min, in ...
Roberts K, Hemmings AJ, Moore-Colyer M, Parker MO, McBride SD.A relationship between dopamine and temperament has previously been described in human cases of dopaminergic dysfunction. Adjustment in temperament prior to disease manifestation can enable the early identification of individuals at risk of such conditions, and scope exists to extend this application of temperament alterations to cases of dopaminergic dysfunction in horses. A multivariate and mixed-methods approach utilising a questionnaire along with two inferred measurements of dopamine activity (Spontaneous Blink Rate [SBR] and behavioral initiation rate [BIR]) were recorded from direct obs...
Haritou SJ, Zylstra R, Ralli C, Turner S, Tortonese DJ.Equine pituitary pars intermedia dysfunction (PPID) is a common and serious condition that gives rise to Cushing's disease. In the older horse, it results in hyperadrenocorticism and disrupted energy metabolism, the severity of which varies with the time of year. To gain insight into the mechanism of its pathogenesis, 24-h profiles for peripheral plasma melatonin, serotonin, dopamine and cortisol concentrations were determined at the winter and summer solstices, and the autumn and spring equinoxes in six horses diagnosed with Cushing's disease and six matched controls. The nocturnal rises in p...
Miller MA, Pardo ID, Jackson LP, Moore GE, Sojka JE.Functional evaluation of the pars intermedia (PI) is required for the early diagnosis of equine pituitary PI dysfunction (PPID), yet most assays target the hypothalamic-pituitary-adrenal axis, which regulates the pars anterior. In contrast, the PI is regulated by dopaminergic tone from hypothalamic neurons. Loss of dopaminergic inhibition is hypothesized to cause the PI hypertrophy and hyperplasia that result in the clinical manifestations of PPID. Domperidone, a dopamine receptor antagonist, should exacerbate the loss of dopaminergic inhibition in horses with PPID and increase the release of ...
Sarkar DK, Smith GC, Fink G.We have investigated the effect of manipulating central catecholamines on the timing of puberty (as assessed by vaginal opening) in female rats and the surge of luteinizing hormone (LH) and gonadotropin releasing hormone (GnRH) induced by pregnant mare serum gonadotropin (PMSG) in immature female rats. Manipulation of the catecholamines was carried out with either 6-hydroxydopamine (6-OHDA) administered with or without either desipramine (DMI) or pargyline, or alpha-methyl-p-tyrosine (alpha-MPT). The neonatal administration of 6-OHDA delayed puberty, an effect which was potentiated by pretreat...
Gerlach T, Aurich JE.This review considers seasonal reproduction in male animals with emphasis on the stallion, ram and hamster. The pineal hormone melatonin is the common link between photoperiod and reproduction. An increase in the daily diurnal period of melatonin secretion is associated with a decrease in GnRH release in long-day breeders, but an increase in GnRH release in short-day breeders. Melatonin influences GnRH release within or close to the mediobasal hypothalamus in rams; whereas melatonin receptors have not been found in the hypothalamus of horses. Prolactin release is positively correlated with day...
Love S.In the horse, adenomata of the pairs intermedia of the pituitary gland have been associated with the distinct clinical entity of Cushing's disease which arises largely as a result of excessive secretion of adrenocorticotropin (ACTH) or other proopiomelanocortin (POMC) peptides. Pars intermedia peptide secretion is under dopaminergic control and compounds such as pergolide or bromocriptine, which are dopamine agonists, can palliate the clinical signs. A variety of endocrinological abnormalities, relevant to both pathogenesis and diagnosis, may be demonstrated in equine Cushing's disease, includ...
Arfuso F, Giannetto C, Giudice E, Fazio F, Panzera M, Piccione G.The current study aimed to investigate whether peripheral modulators of serotoninergic function and neurohumoral factors' changes in athletic horses during an official jumping competition, and to evaluate their relationship with the physical performance of competing horses. From 7 Italian Saddle mares (6-9 years; mean body weight 440 ± 15 kg), performing the same standardized warm-up and jumping course during an official class, heart rate (HR) was monitored throughout the competition. Rectal temperature (RT) measurement, blood lactate and glucose concentration, serum tryptophan, leucine, vali...
Tatum RC, McGowan CM, Ireland JL.Pergolide, a dopamine agonist, is commonly administered to manage pituitary pars intermedia dysfunction (PPID), a progressive neurodegenerative disease prevalent in aged horses. However, available evidence regarding pergolide's efficacy in improving clinical and endocrine parameters is limited. The aim of this systematic review was to assess published literature and evaluate evidence regarding whether pergolide treatment results in improvement of clinical signs and/or adrenocorticotrophic hormone (ACTH) concentration compared to no treatment or other unlicensed treatments. Systematic searches ...
Bae SE, Corcoran BM, Watson ED.Little is known about neurogenic regulation of uterine contractility in mares. The present study investigated the distribution of adrenergic and peptidergic nerves in the mare uterus. Samples from the uterine horn, body and cervix were collected from 18 cyclic mares for immunohistochemistry. The uterus was well supplied with adrenergic nerves. A large number of tyrosine hydroxylase- and dopamine beta-hydroxylase-immunoreactive nerve bundles and fibres were present in the myometrium and endometrium in all regions of the uterus and cervix. These adrenergic nerve bundles and fibres travelled para...
McGorum BC, Pirie RS, Eaton SL, Keen JA, Cumyn EM, Arnott DM, Chen W, Lamont DJ, Graham LC, Llavero Hurtado M, Pemberton A, Wishart TM.Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of ∼2%. An apparently identical disease occurs in multiple species, including but not limited to cats, dogs, and rabbits. Although the precise etiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here, we use a bottom-up approach be...
Durham AE.Equine endocrine disease is commonly encountered by equine practitioners. Pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS) predominate. The most logical therapeutic approach in PPID uses dopamine agonists; pergolide mesylate is the most common. Bromocryptine and cabergoline are alternative drugs with similar actions. Drugs from other classes have a poor evidence basis, although cyproheptadine and trilostane might be considered. EMS requires management changes as the primary approach; reasonable justification for use of drugs such as levothyroxine and metformin m...
Millington WR, Dybdal NO, Dawson R, Manzini C, Mueller GP.Equine Cushing's disease is caused by an adenomatous hyperplasia of the intermediate pituitary which secretes high levels of beta-endorphin, ACTH, and other peptide derivatives of POMC. In the present study we found that plasma and cerebrospinal fluid immunoreactive beta-endorphin (i beta-endorphin) levels were 60- and 120-fold higher than control values in horses with Cushing's disease. There were no significant differences in intermediate lobe i beta-endorphin concentrations, although anterior lobe i beta-endorphin was significantly reduced in Cushing's horses, presumably because high levels...
Duke T, Filzek U, Read MR, Read EK, Ferguson JG.During an 8-year period of clinic improvements, an increased incidence of postanesthetic myopathy (PAM) was observed in horses undergoing anesthesia. A request was made for an independent anesthesiologist to examine possible reasons for this increase. Routine methods used for anesthesia were then compared with new methods introduced by the anesthesiologist. Methods: Investigative observations were conducted from October 1999 to April 2000. Following premedication with xylazine or detomidine, anesthesia was induced with diazepam or guiaifenesin followed by ketamine. Maintenance of anesthesia wa...
Cozzi B, Pellegrini M, Droghi A.The structure and histochemical properties of neuromelanin in the Substantia nigra of the horse were studied by light and electron microscopy. Morphological, histochemical and cytochemical evidences showed the presence of a melanin component in some pigment granules, even if a large quantity of granules displayed only the properties of lipofuscins. Pigment formation in the neurons of the Substantia nigra of the horse may take place through the tyrosine-tyrosinase enzymatic pathway, as shown by positive Dopa-reaction. The results obtained were discussed in reference to the possible use of melan...
Tukov FF, Rimoldi JM, Matthews JC.Repin, a major constituent in extracts of the plant Centaurea repens is thought to be the active principal responsible for the development of equine nigropallidal encephalomalacia (ENE), a fatal Parkinson-like neurodegenerative disorder in horses. Although the exact mechanism by which ingestion of this weed causes ENE is uncertain, a limited body of experimental evidence suggests a critical role for the glutathione redox system. In the present study, the mechanism of repin neurotoxicity was examined in PC12 cells with a focus on determining the role of glutathione (GSH) in repin-induced mitoch...
Lee YH, Clarke KW, Alibhai HI, Song D.To evaluate the effect on intramuscular blood flow (IMBF) and hemodynamic variables of 4 antihypotensive agents given during anesthesia. Methods: 8 ponies. Methods: Halothane-anesthetized ponies (n = 6) positioned in lateral recumbency received, on separate occasions, infusions of each of the following 4 agents in serially increasing dosages or saline solution: phenylephrine hydrochloride (0.25, 0.5, 1, and 2 microg/kg of body weight), dopamine (2.5, 5, 10, and 20 microg/kg), dobutamine (1, 2.5, 5, and 10 microg/kg), and dopexamine (0.5, 1, 5, and 10 microg/kg). Changes in IMBF (by laser-Doppl...
McBride SD, Hemmings A.Stress-induced changes in mesoaccumbens dopamine neurophysiology have been associated with the development of stereotypic behaviour in in-bred strains of laboratory rodents. This experiment evaluated whether similar changes are associated with environmentally-induced stereotypic behaviour in a higher-vertebrate species, the horse. D1- and D2-like dopamine receptor densities (B(max)) and dissociation constants (K(d)) were measured in control (n=9) and stereotypy (n=9) horses in the nucleus accumbens, caudate nucleus, putamen, substantia nigra and ventral tegmentum brain regions. Results reveale...
Bantle CM, Rocha SM, French CT, Phillips AT, Tran K, Olson KE, Bass TA, Aboellail T, Smeyne RJ, Tjalkens RB.Viral infection of the central nervous system (CNS) can cause lasting neurological decline in surviving patients and can present with symptoms resembling Parkinson's disease (PD). The mechanisms underlying postencephalitic parkinsonism remain unclear but are thought to involve increased innate inflammatory signaling in glial cells, resulting in persistent neuroinflammation. We therefore studied the role of glial cells in regulating neuropathology in postencephalitic parkinsonism by studying the involvement of astrocytes in loss of dopaminergic neurons and aggregation of α-synuclein protein fo...
Spelta CW.Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally do...
Gerring EE, Hunt JM.An experimental model of postoperative ileus was developed in ponies using trauma to, and exposure of, a length of small intestine which gave rise to a reproducible and reversible set of changes in gut activity. This was assessed by recordings of electrical and mechanical activity and by propulsion of spheres from stomach to anus. Activity was depressed, especially in the stomach and colon, and transit was slowed. All drugs given increased electromechanical activity but propranolol was the least effective and did not alter the delayed transit of spheres. Yohimbine was more effective and the ad...
Parker M, McBride SD, Redhead ES, Goodwin D.Significant similarities exist between the neural and behavioural features of environmentally and drug-induced stereotypy. For example, exposure to dopamine agonists, such as amphetamine, induces stereotypy and causes alterations in midbrain neurophysiology similar to those observed following chronic stress. An additional behavioural feature of these neural changes in the drug-induced phenotype is an enhanced rate of switching from response-outcome (R-O) to stimulus-response (S-R) learning. The aim of the current experiment was to examine R-O and S-R learning in horses displaying environmental...
Wang N, Zhang D, Deng X, Sun Y, Wang X, Ma P, Song D.Herein we report a novel polydopamine-silver nanoparticle-polydopamine-gold (PDA-AgNPs-PDA-Au) film based surface plasmon resonance (SPR) biosensor for horse IgG detection. The PDA-AgNPs-PDA-Au film sensing platform was built on Au-film via layer-by-layer self-assembly. Ag ion was reduced in situ to AgNPs in presence of PDA. The top PDA layer can prevent AgNPs from being oxidized and connect with antibody via Schiff alkali reaction directly. The morphology and thickness of the modified gold film were characterized using scanning electron microscope and Talystep. Experimental results show that ...
Blodgett DJ.Most of the tall fescue pastures in the United States are infected by an endophyte, N. coenophialum. The fungus derives nutrients from the plant while supplying the plant with toxins for defense. The most detrimental toxins for animals in tall fescue are ergopeptine alkaloids, especially ergovaline. Ergovaline functions as a dopamine D2 agonist and alters prolactin and several other hormones in the body. Pregnant mares are most susceptible during their last month of gestation. Clinical signs include prolonged gestation, dystocia, retained placentas, agalactia, and dysmature foals that are eith...
Swanson CR, Muir WW, Bednarski RM, Skarda RT, Hubbell JA.The hemodynamic changes induced by constant infusions of dopamine or dobutamine (each 3, 5, and 10 micrograms/kg/min) were observed in halothane-anesthetized horses. Left ventricular dp/dt and cardiac output were increased in horses given dobutamine at dosage of 3 micrograms/kg/min and in those given either of the drugs at dosages of 5 and 10 micrograms/kg/min. Concomitant increases in systemic arterial blood pressure occurred at lower infusion dosage rates of dobutamine than those of dopamine and were modulated by dosage-related changes in peripheral vascular resistance that were different be...
