Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages

The estrous cycle involves hormonal fluctuations that influence serotonin (5-HT) concentrations and immune cell activity. During the follicular phase, estrogen increases 5-HT synthesis, enhancing cellular responses to inflammation. In contrast, in the luteal phase, progesterone suppresses immune fun...

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Main Authors: Katiuska Satué, Deborah La Fauci, Pietro Medica, María Gemma Velasco-Martínez, Giuliana Barbiera, Esterina Fazio
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Veterinary Sciences
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Online Access:https://www.mdpi.com/2306-7381/12/6/548
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author Katiuska Satué
Deborah La Fauci
Pietro Medica
María Gemma Velasco-Martínez
Giuliana Barbiera
Esterina Fazio
author_facet Katiuska Satué
Deborah La Fauci
Pietro Medica
María Gemma Velasco-Martínez
Giuliana Barbiera
Esterina Fazio
author_sort Katiuska Satué
collection DOAJ
description The estrous cycle involves hormonal fluctuations that influence serotonin (5-HT) concentrations and immune cell activity. During the follicular phase, estrogen increases 5-HT synthesis, enhancing cellular responses to inflammation. In contrast, in the luteal phase, progesterone suppresses immune function, reducing 5-HT availability. Age-related changes in hormone concentrations can affect these processes, potentially altering cellular responses and 5-HT dynamics in the oldest females. This study hypothesizes the relationship between 5-HT and blood cells in healthy cyclic mares, considering age as an influencing factor. Understanding these interactions offers insights into reproductive health and immune regulation in equine species. The aim was to describe the interaction between 5-HT and blood cells in twenty-five healthy cyclic Spanish Purebred mares, evaluating the effect of aging. For this purpose, the mares were classified into two age groups as follows: from 4 to 9 years (<i>n</i> = 12 younger mares) and from 10 to 15 years (<i>n</i> = 13 older mares). Younger and older mares showed an opposite 5-HT trend at +5 and +16 day of cycle (d), with greater concentrations in younger mares (<i>p</i> < 0.05) and lower values in older mares (<i>p</i> < 0.05) than at −5 and 0 d. Older mares showed a lower 5-HT concentration at +5 and +16 d (<i>p</i> < 0.05) than younger mares. Mares of both ages showed a superimposed WBC trend, with the greatest number both at −5 and 0 d (<i>p</i> < 0.05). Older mares showed a lower WBC number at −5 d (<i>p</i> < 0.05), and lower NFS and LYMPH numbers both at +5 and +16 d (<i>p</i> < 0.05) than younger mares; the latter showed the lowest NFS number at +16 d, and LYMPH number at +5 and +16 d. Mares of both ages showed a similar trend for the N/L ratio. Older mares showed a lower MON number at +5 d (<i>p</i> < 0.05), greater PLTs at +5 and +16 d (<i>p</i> < 0.05) than younger mares, and a greater PLT number at −5 and 0 d than at +5 and +16 d (<i>p</i> < 0.05). The activity of 5-HT is regulated by its rate of synthesis, release, and metabolism according to age. Aging reduced the 5-HT concentrations and the number of WBCs, NFSs, LYMPHs, and MONs, inducing correlations among these and 5-HT in healthy young and old cyclic mares.
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spelling doaj-art-24455a11e4e3485a9e7bc6c2c3432d3f2025-08-20T02:21:52ZengMDPI AGVeterinary Sciences2306-73812025-06-0112654810.3390/vetsci12060548Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different AgesKatiuska Satué0Deborah La Fauci1Pietro Medica2María Gemma Velasco-Martínez3Giuliana Barbiera4Esterina Fazio5Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, CEU-Cardenal Herrera University, Tirant lo Blanc, 7, Alfara del Patriarca, 46115 Valencia, SpainDepartment of Veterinary Sciences, Veterinary Physiology Unit, Polo Universitario Annunziata, Via Palatucci 13, 98168 Messina, ItalyDepartment of Veterinary Sciences, Veterinary Physiology Unit, Polo Universitario Annunziata, Via Palatucci 13, 98168 Messina, ItalyDepartment of Veterinary Sciences, Veterinary Physiology Unit, Polo Universitario Annunziata, Via Palatucci 13, 98168 Messina, ItalyPharmaceutical and Chemical Technician, 98168 Messina, ItalyDepartment of Veterinary Sciences, Veterinary Physiology Unit, Polo Universitario Annunziata, Via Palatucci 13, 98168 Messina, ItalyThe estrous cycle involves hormonal fluctuations that influence serotonin (5-HT) concentrations and immune cell activity. During the follicular phase, estrogen increases 5-HT synthesis, enhancing cellular responses to inflammation. In contrast, in the luteal phase, progesterone suppresses immune function, reducing 5-HT availability. Age-related changes in hormone concentrations can affect these processes, potentially altering cellular responses and 5-HT dynamics in the oldest females. This study hypothesizes the relationship between 5-HT and blood cells in healthy cyclic mares, considering age as an influencing factor. Understanding these interactions offers insights into reproductive health and immune regulation in equine species. The aim was to describe the interaction between 5-HT and blood cells in twenty-five healthy cyclic Spanish Purebred mares, evaluating the effect of aging. For this purpose, the mares were classified into two age groups as follows: from 4 to 9 years (<i>n</i> = 12 younger mares) and from 10 to 15 years (<i>n</i> = 13 older mares). Younger and older mares showed an opposite 5-HT trend at +5 and +16 day of cycle (d), with greater concentrations in younger mares (<i>p</i> < 0.05) and lower values in older mares (<i>p</i> < 0.05) than at −5 and 0 d. Older mares showed a lower 5-HT concentration at +5 and +16 d (<i>p</i> < 0.05) than younger mares. Mares of both ages showed a superimposed WBC trend, with the greatest number both at −5 and 0 d (<i>p</i> < 0.05). Older mares showed a lower WBC number at −5 d (<i>p</i> < 0.05), and lower NFS and LYMPH numbers both at +5 and +16 d (<i>p</i> < 0.05) than younger mares; the latter showed the lowest NFS number at +16 d, and LYMPH number at +5 and +16 d. Mares of both ages showed a similar trend for the N/L ratio. Older mares showed a lower MON number at +5 d (<i>p</i> < 0.05), greater PLTs at +5 and +16 d (<i>p</i> < 0.05) than younger mares, and a greater PLT number at −5 and 0 d than at +5 and +16 d (<i>p</i> < 0.05). The activity of 5-HT is regulated by its rate of synthesis, release, and metabolism according to age. Aging reduced the 5-HT concentrations and the number of WBCs, NFSs, LYMPHs, and MONs, inducing correlations among these and 5-HT in healthy young and old cyclic mares.https://www.mdpi.com/2306-7381/12/6/548age5-HTimmune cellscyclic mares
spellingShingle Katiuska Satué
Deborah La Fauci
Pietro Medica
María Gemma Velasco-Martínez
Giuliana Barbiera
Esterina Fazio
Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
Veterinary Sciences
age
5-HT
immune cells
cyclic mares
title Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
title_full Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
title_fullStr Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
title_full_unstemmed Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
title_short Involvement of Peripheral Serotonin in Blood Cells in Healthy Cyclical Mares of Different Ages
title_sort involvement of peripheral serotonin in blood cells in healthy cyclical mares of different ages
topic age
5-HT
immune cells
cyclic mares
url https://www.mdpi.com/2306-7381/12/6/548
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AT mariagemmavelascomartinez involvementofperipheralserotonininbloodcellsinhealthycyclicalmaresofdifferentages
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