Evaluation of age effect on circulating catecholamines' network in pregnant mares.

Catecholamines (CATs) are essential neuroendocrine regulators with plasma concentrations that naturally fluctuate during pregnancy. Age-related changes in CATs, observed in humans and animals, suggest that gestation and aging together influence catecholaminergic activity. Blood samples were collected from Spanish Purebred mares categorized into three age cohorts (4-7 years, n = 18; 8-10 years, n = 18; 11-15 years, n = 18) across four defined gestational stages: first trimester (T1), second trimester (T2), third trimester (T3), and the final bimester (B4). Plasma concentrations of adrenaline (A), noradrenaline (NA), and dopamine (DA) were quantified using a horse-specific validated competitive enzyme immunoassay (3-CAT EIA). CATs during gestation showed age-dependent patterns: A declined from T1 to T2 (p < 0.05), stabilizing or slightly increasing at T3-B4; mares 8-10 years had greatest A at T1, while 11-15 years maintained greater A concentrations at T2. NA was elevated in younger mares (4-7 years) in late gestation (p ≤ 0.05), with the lowest concentrations in mares of 8-10 years. DA peaked in mid-gestation and decreased before parturition (p ≤ 0.05), with older mares that display a more stable profile. These findings highlight age-related modulation of neuroendocrine function during pregnancy.