Journal of neuroendocrinology.
Publisher:
Oxford University Press,. Malden, MA : Wiley & Sons (2010)
Frequency: Monthly,
Country: United States
Language: English
Start Year:1989 -
ISSN:
0953-8194 (Print)
1365-2826 (Electronic)
0953-8194 (Linking)
1365-2826 (Electronic)
0953-8194 (Linking)
Impact Factor
3.2
2022
| NLM ID: | 8913461 |
| (DNLM): | SR0065709(s) |
| (OCoLC): | 20225561 |
| Coden: | JOUNE2 |
| LCCN: | sn 89036459 |
| Classification: | W1 JO787C |
Melatonin receptors and thyroid stimulating hormone in the equine pars tuberalis: Potential modulators of seasonal reproduction in the mare. The mechanism by which photoperiod influences the hypothalamic-pituitary-gonadal (HPG) axis and regulates seasonal reproduction in horses has yet to be fully elucidated. The hypophyseal pars tuberalis (PT) has been indicated as a critical site for the transduction of melatonin signals through melatonin-responsive, PT-specific cells that produce thyroid-stimulating hormone (TSH) in many mammalian species. However, this has yet to be investigated in horses. The objective of this study was to explore the interaction of melatonin and thyroid-stimulating hormone in the equine HPG axis. Pituitaries ...
Experimental jetlag disrupts circadian clock genes but improves performance in racehorses after light-dependent rapid resetting of neuroendocrine systems and the rest-activity cycle. Abrupt alterations in the 24-h light : dark cycle, such as those resulting from transmeridian air travel, disrupt circadian biological rhythms in humans with detrimental consequences on cognitive and physical performance. In the present study, a jetlag-simulated phase shift in photoperiod temporally impaired circadian peaks of peripheral clock gene expression in racehorses but acutely enhanced athletic performance without causing stress. Indices of aerobic and anaerobic capacities were significantly increased by a phase-advance, enabling prolonged physical activity before fatigue occurred. Thi...
Role of prolactin in the gonadotroph responsiveness to gonadotrophin-releasing hormone during the equine annual reproductive cycle. A combined suppressive effect of prolactin (PRL) and dopamine on the secretion of luteinising hormone (LH) at the level of the pituitary gland has been identified in sheep, a short-day breeder. However, little is known about the role of PRL in the intra-pituitary regulation of the gonadotrophic axis in long-day breeders. In the present study, we investigated the effects of PRL on LH and follicle-stimulating hormone (FSH) secretion during the equine annual reproductive cycle. Horse pituitaries were obtained during the breeding season (BS) and nonbreeding season (NBS). Cells were dispersed, plat...
Seasonal changes in circadian peripheral plasma concentrations of melatonin, serotonin, dopamine and cortisol in aged horses with Cushing’s disease under natural photoperiod. 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...
Nitration and increased alpha-synuclein expression associated with dopaminergic neurodegeneration in equine pituitary pars intermedia dysfunction. 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...
Inter-relationships between the secretory dynamics of thyrotrophin-releasing hormone, thyrotrophin and prolactin in periovulatory mares: effect of hypothyroidism. We used our nonsurgical technique for collecting pituitary venous blood to relate the dynamics of thyrotrophin-releasing hormone (TRH) secretion to the secretion patterns of both prolactin and thyrotrophin in periovulatory mares, either euthyroid (n = 5) or made hypothyroid by treatment with propyl-thiouracil (n = 5). Pituitary venous blood was collected continuously and divided into 1-min aliquots for 4 h. To test the effect of dopamine on the relationship between secretion patterns, sulpiride, a selective D2 receptor antagonist, was given i.m. after 2 h of sampling. Thorough testing of the m...
Gonadotroph heterogeneity, density and distribution, and gonadotroph-lactotroph associations in the pars distalis of the male equine pituitary gland. The intrapituitary mechanisms regulating gonadotrophin secretion in the horse remain unclear. Here, we examined seasonal and gonadal effects on the gonadotroph and lactotroph populations of male horses with the aim of defining a possible morphological basis for the differential release of gonadotrophins. Pituitaries were collected from: (i) gonadal-intact horses in the breeding season (GBS); (ii) orchidectomized horses in the breeding season (OBS); and (iii) orchidectomized horses in the nonbreeding season (ONBS). Immunohistochemistry was performed using antibodies to the luteinizing hormone (...
Effects of novelty stress on neuroendocrine activities and running performance in thoroughbred horses. This study investigated the effects of novelty stress on neuroendocrine activities and running performance in Thoroughbred horses. First, to examine the neuroendocrine responses to novelty stress, we exposed horses to two types of novel environmental stimuli (audiovisual or novel field stimuli). After the stimuli, plasma concentrations of vasopressin, catecholamines and adrenocorticotropin (ACTH), as well as heart rates, were significantly increased in each experiment. Second, we investigated neuroendocrine activities during incremental exercise. Plasma concentrations of vasopressin, catechola...
The effect of endotoxin administration on the secretory dynamics of oxytocin in follicular phase mares: relationship to stress axis hormones. The primary aim of this study was to define the secretory dynamics of oxytocin and vasopressin in pituitary venous effluent from ambulatory horses during acute endotoxaemia, a stimulus that may release both hormones. Our secondary aim was to investigate the role of oxytocin in regulating adrenocorticotropic hormone (ACTH) secretion by comparing oxytocin, vasopressin, corticotropin-releasing hormone (CRH) and ACTH secretory profiles during endotoxaemia and by monitoring the ACTH response to oxytocin administration. Pituitary venous blood was collected nonsurgically continuously and divided into...
The effect of the alpha-2-adrenergic agonist, clonidine, on secretion patterns and rates of adrenocorticotropic hormone and its secretagogues in the horse. Alpha-2-adrenoceptor activation may lower adrenocorticotropic hormone (ACTH) by reducing secretagogue input and/or increasing the release of an inhibitory factor (CIF). To investigate this, we gave clonidine, an alpha-2-agonist, to seven horses, and collected pituitary venous blood every minute for 20 min before treatment and 40 min after treatment. Six horses were given saline vehicle. Mean secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and ACTH were calculated before and during four 5-min then two 10-min periods after clonidine or saline. Reduction in A...