title: Oxytocin treatment does not change cardiovascular parameters, hematology and plasma electrolytes in parturient horse mares.
abstract: In mares, foaling is associated with changes in hematology, plasma electrolytes, blood pressure and heart rate and it has been hypothesized that these are induced by oxytocin. To test this hypothesis, mares (n = 8-14/group) were treated with oxytocin (OT; 20 I.U.) or saline (CON) at 1 h (test A) and 12 h after foaling (test B) and during first postpartum diestrus (test C). Heart rate, heart rate variability (HRV), atrioventricular blocks, salivary cortisol concentration, blood pressure, plasma electrolytes and blood count were determined. Heart rate decreased from test A to C (P < 0.001) but at no time differed between groups. The HRV, blood pressure and occurrence of atrioventricular blocks did not change in response to oxytocin. Cortisol concentration decreased from test A to C (P < 0.001). Oxytocin induced a cortisol release in test B (time x treatment P < 0.001, time x test P < 0.001). Plasma sodium and chloride concentrations decreased from test A to C (P < 0.001) but did not differ between groups. In test A, potassium concentration increased in CON but not OT mares (time P < 0.01, time x test P < 0.01, time x treatment P < 0.05). Polymorphnuclear cell (PMN) numbers in blood decreased from test A to C (P < 0.001) while lymphocytes increased (P < 0.05). At no time PMN and lymphocytes differed between groups. Oxytocin treatment had no effect on skin temperature. In conclusion, except for a limited effect on cortisol release, oxytocin was without effect and the hypothesis of oxytocin-induced alterations in cardiac parameters, plasma electrolytes and hematology of foaling mares was not verified.
authors.affiliation: Graf Lehndorff Institute for Equine Science, Vetmeduni Vienna, 16845 Neustadt/Dosse, Germany. Electronic address: christina.nagel@vetmeduni.ac.at.
authors.forename: Christina
authors.initials: C
authors.lastname: Nagel
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, Vetmeduni Vienna, 1210 Vienna, Austria. Electronic address: lisa.trenk@vetmeduni.ac.at.
authors.forename: Lisa
authors.initials: L
authors.lastname: Trenk
authors.affiliation: Graf Lehndorff Institute for Equine Science, Vetmeduni Vienna, 16845 Neustadt/Dosse, Germany. Electronic address: manuela.wulf@vetmeduni.ac.at.
authors.forename: Manuela
authors.initials: M
authors.lastname: Wulf
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, Vetmeduni Vienna, 1210 Vienna, Austria. Electronic address: natascha.ille@vetmeduni.ac.at.
authors.forename: Natascha
authors.initials: N
authors.lastname: Ille
authors.affiliation: Section for Obstetrics, Gynecology and Andrology, Vetmeduni Vienna, 1210 Vienna, Austria. Electronic address: joerg.aurich@vetmeduni.ac.at.
authors.forename: Jörg
authors.initials: J
authors.lastname: Aurich
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, Vetmeduni Vienna, 1210 Vienna, Austria. Electronic address: christine.aurich@vetmeduni.ac.at.
authors.forename: Christine
authors.initials: C
authors.lastname: Aurich
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology; D001794:Blood Pressure / Q000187:drug effects; D004573:Electrolytes / Q000097:blood*; D005260:Female; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood; D010121:Oxytocin / Q000494:pharmacology*; D036801:Parturition / Q000187:drug effects* / Q000502:physiology; D011247:Pregnancy
chemical_list: D004573:Electrolytes; D010121:Oxytocin; D006854:Hydrocortisone
keywords: Cardiac arrhythmia; Hematology; Horse; Oxytocin; Parturition