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Home / Equine Research Bank / J Neuroendocrinol / Seasonal changes in circadian peripheral plasma concentratio...
Journal of neuroendocrinology2008; 20(8); 988-996; doi: 10.1111/j.1365-2826.2008.01751.x

Seasonal changes in circadian peripheral plasma concentrations of melatonin, serotonin, dopamine and cortisol in aged horses with Cushing’s disease under natural photoperiod.

Abstract: 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 plasma melatonin concentrations, although different across seasons, were broadly of the same duration and similar amplitude in both groups of animals (P > 0.05). The plasma concentrations of cortisol did not show seasonal variation and were different in diseased horses only in the summer when they were higher across the entire 24-h period (P < 0.05). Serotonin concentrations were not significantly affected by time of year but tended to be lower in Cushingoid horses (P = 0.07). By contrast, dopamine output showed seasonal variation and was significantly lower in the Cushing's group in the summer and autumn (P < 0.05). The finding that the profiles of circulating melatonin are similar in Cushingoid and control horses reveals that the inability to read time of year by animals suffering from Cushing's syndrome is an unlikely reason for the disease. In addition, the results provide evidence that alterations in the dopaminergic and serotoninergic systems may participate in the pathogenesis of PPID.
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Publication Date: 2008-06-06 PubMed ID: 18540997PubMed Central: PMC2658710DOI: 10.1111/j.1365-2826.2008.01751.xGoogle Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research investigates levels of several hormones in horses affected by Equine pituitary pars intermedia dysfunction (PPID or Cushing’s Disease) across different seasons. The study doesn’t find a significant time-based disruption to melatonin, suggesting that loss of seasonal perception isn’t a factor in this disease. Yet, it indicates that altered dopamine and serotonin systems may play a part in the onset of the condition.

Research Objective and Methodology

  • The study aimed to shed light on the mechanism causing PPID, a disorder leading to Cushing’s disease in older horses.
  • This condition results in hyperadrenocorticism (overactivity of the adrenal cortex), disrupts energy metabolism, and its severity differs by season.
  • To investigate this, the team studied peripheral plasma concentrations of four hormones—melatonin, serotonin, dopamine, and cortisol—in horses diagnosed with Cushing’s disease.
  • The levels of these hormones were observed at four points: the winter and summer solstices, and the autumn and spring equinoxes.
  • The test group consisted of six horses suffering from Cushing’s disease, with six matched controls for comparison.

Main Findings

  • The analysis of plasma melatonin showed that the duration and amplitude of nocturnal increases were mostly consistent in both sets of animals, regardless of season.
  • Cortisol levels didn’t show seasonal fluctuation but were found to be higher in Cushing’s-affected horses during summer.
  • Although serotonin levels didn’t significantly alter across seasons, they tended to be lower in the horses with Cushing’s disease.
  • Dopamine concentration exhibited seasonal variation and was lower in Cushing’s-affected horses in summer and autumn.

Conclusive Insights

  • The similar melatonin profiles in both study groups suggest that an inability to perceive seasonal changes doesn’t likely cause Cushing’s disease.
  • The research, however, provides evidence that the serotonergic and dopaminergic systems’ alterations might contribute to the development of PPID.

Cite This Article

APA
Haritou SJ, Zylstra R, Ralli C, Turner S, Tortonese DJ. (2008). Seasonal changes in circadian peripheral plasma concentrations of melatonin, serotonin, dopamine and cortisol in aged horses with Cushing’s disease under natural photoperiod. J Neuroendocrinol, 20(8), 988-996. https://doi.org/10.1111/j.1365-2826.2008.01751.x

Publication

Journal of neuroendocrinology
ISSN: 1365-2826
NlmUniqueID: 8913461
Country: United States
Language: English
Volume: 20
Issue: 8
Pages: 988-996

Researcher Affiliations

Haritou, S J A
  • Pegasus Equine Diagnostics Ltd, BioCity Nottingham, Nottingham, UK.
Zylstra, R
    Ralli, C
      Turner, S
        Tortonese, D J

          MeSH Terms

          • Aging / blood
          • Animals
          • Case-Control Studies
          • Circadian Rhythm / physiology
          • Dopamine / blood
          • Horses / blood
          • Hydrocortisone / blood
          • Melatonin / blood
          • Photoperiod
          • Pituitary ACTH Hypersecretion / blood
          • Pituitary ACTH Hypersecretion / veterinary
          • Seasons
          • Serotonin / blood

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