https://phaidra.vetmeduni.ac.at/o:5440 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 Rattanathanya, Hathaipat Hathaipat Rattanathanya University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Binetti, Anna Anna Binetti 0000-0002-4042-9106 University of Veterinary Medicine Vienna. Clinical Centre for Small Animal Health and Research Pohlin, Friederike Friederike Pohlin 0000-0002-4236-5847 University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Ferreira, Susana C.M. Susana C.M. Ferreira 0000-0003-0265-0210 University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Braun, Christina Christina Braun 0000-0002-4547-6278 University of Veterinary Medicine Vienna. Clinical Centre for Small Animal Health and Research Schramel, Johannes Johannes Schramel 0000-0002-3254-370X University of Veterinary Medicine Vienna. Clinical Centre for Small Animal Health and Research Meyer, Leith C.R. Leith C.R. Meyer Haw, Anna Anna Haw University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Raekallio, Marja Marja Raekallio Böhmdorfer, Stefan Stefan Böhmdorfer Kalogeropoulu, Szilvia Szilvia Kalogeropoulu 0000-0002-3689-6369 University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Mosing, Martina Martina Mosing 0000-0002-6190-5642 University of Veterinary Medicine Vienna. Clinical Centre for Small Animal Health and Research Stalder, Gabrielle Gabrielle Stalder 0000-0002-8901-1181 University of Veterinary Medicine Vienna. Research Institute of Wildlife Ecology Springer journal article open access eng 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. BIMU-8 Etorphine Opioid Vatinoxan Pulmonary Hypertension Cardiovascular http://creativecommons.org/licenses/by/4.0/ https://phaidra.vetmeduni.ac.at/api/object/o:5440/download 10.1186/s12917-026-05379-x https://phaidra.vetmeduni.ac.at/o:605 application/pdf BMC Veterinary Research issn:1746-6148 VoR BMC Veterinary Research 22 1 1.80 MB 2026