University of Veterinary Medicine Vienna Cardiovascular effects of a selective 5-HT4 agonist and an alpha-2 adrenoceptor antagonist in etorphine immobilised sheep (Ovis aries) - a randomised, prospective, and controlled trial Background Etorphine, a highly potent opioid widely used in wildlife immobilisation, is known to cause cardiorespiratory compromise. This study aimed to investigate the effects of a serotonergic agonist, BIMU-8 and an alpha-2 adrenoreceptor antagonist, vatinoxan on pulmonary hypertension and cardiovascular function in etorphine-immobilised sheep, as a model for wild ungulates. Six sheep were immobilised three times in a randomised, prospective, controlled crossover design using intramuscular etorphine (0.05 mg·kg−1). Seven minutes later, sheep received intravenous BIMU-8 (1.5 mg·kg−1), vatinoxan (0.15 mg·kg−1), or sterile water (control). Respiratory rate, pulmonary arterial, systemic arterial and central venous pressures, electrocardiography, heart rate, and cardiac output were recorded. Data were collected at resting state, six minutes post-etorphine, and at six-minute intervals post-treatment. Naltrexone was administered 19 minutes post-treatment to reverse immobilisation. Linear mixed-effects models were used for statistical analysis. Results Etorphine induced bradypnea, pulmonary hypertension, dysrhythmias, and tachycardia in sheep. BIMU-8 significantly reduced mean pulmonary arterial pressure (F2,91 = 4.17, p = 0.02) and mean arterial pressure (F2,89 = 6.01, p < 0.01) but was associated with severe tachydysrhythmia. Vatinoxan decreased respiratory rate (F2,91 = 4.13, p < 0.01), increased cardiac output (F2,91 = 10.88, p < 0.01), and reduced body temperature (F6,85 = 2.2, p = 0.05), while having no effect on pulmonary or systemic arterial pressures. Conclusion BIMU-8 reduces etorphine-induced pulmonary and systemic hypertension, but causes tachydysrhythmias, requiring further evaluation. Vatinoxan improves cardiac output, without alleviating pulmonary hypertension in etorphine-immobilised sheep. en TEXT journal article Wissenschaftlicher Artikel Articolo scientifico Text journal article Documento PDF Articolo scientifico Text Wissenschaftlicher Artikel BIMU-8 Etorphine Opioid Vatinoxan Pulmonary Hypertension Cardiovascular 2026 2026 Hathaipat Rattanathanya (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Anna Binetti (Clinical Centre for Small Animal Health and Research, Clinical Department for Small Animals and Horses, Departments, University of Veterinary Medicine Vienna) Friederike Pohlin (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Susana C.M. Ferreira (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Christina Braun (Clinical Centre for Small Animal Health and Research, Clinical Department for Small Animals and Horses, Departments, University of Veterinary Medicine Vienna) Johannes Schramel (Clinical Centre for Small Animal Health and Research, Clinical Department for Small Animals and Horses, Departments, University of Veterinary Medicine Vienna) Leith C.R. Meyer Anna Haw (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Marja Raekallio Stefan Böhmdorfer Szilvia Kalogeropoulu (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Martina Mosing (Clinical Centre for Small Animal Health and Research, Clinical Department for Small Animals and Horses, Departments, University of Veterinary Medicine Vienna) Gabrielle Stalder (Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, Departments, University of Veterinary Medicine Vienna) Springer