phaidra.vetmeduni.ac.at o:5440 DOI 10.1186/s12917-026-05379-x 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. eng BIMU-8 Etorphine Opioid Vatinoxan Pulmonary Hypertension Cardiovascular 2026-08-21T08:32:38.968Z LOMv1.0 Author BEGIN:VCARD VERSION:3.0 N:Rattanathanya;Hathaipat; FN:Hathaipat Rattanathanya END:VCARD BEGIN:VCARD VERSION:3.0 N:Binetti;Anna; FN:Anna Binetti X-ORCID:https://orcid.org/0000-0002-4042-9106 END:VCARD BEGIN:VCARD VERSION:3.0 N:Pohlin;Friederike; FN:Friederike Pohlin X-ORCID:https://orcid.org/0000-0002-4236-5847 END:VCARD BEGIN:VCARD VERSION:3.0 N:Ferreira;Susana C.M.; FN:Susana C.M. Ferreira X-ORCID:https://orcid.org/0000-0003-0265-0210 END:VCARD BEGIN:VCARD VERSION:3.0 N:Braun;Christina; FN:Christina Braun X-ORCID:https://orcid.org/0000-0002-4547-6278 END:VCARD BEGIN:VCARD VERSION:3.0 N:Schramel;Johannes; FN:Johannes Schramel X-ORCID:https://orcid.org/0000-0002-3254-370X END:VCARD BEGIN:VCARD VERSION:3.0 N:Meyer;Leith C.R.; FN:Leith C.R. Meyer END:VCARD BEGIN:VCARD VERSION:3.0 N:Haw;Anna; FN:Anna Haw END:VCARD BEGIN:VCARD VERSION:3.0 N:Raekallio;Marja; FN:Marja Raekallio END:VCARD BEGIN:VCARD VERSION:3.0 N:Böhmdorfer;Stefan; FN:Stefan Böhmdorfer END:VCARD BEGIN:VCARD VERSION:3.0 N:Kalogeropoulu;Szilvia; FN:Szilvia Kalogeropoulu X-ORCID:https://orcid.org/0000-0002-3689-6369 END:VCARD BEGIN:VCARD VERSION:3.0 N:Mosing;Martina; FN:Martina Mosing X-ORCID:https://orcid.org/0000-0002-6190-5642 END:VCARD BEGIN:VCARD VERSION:3.0 N:Stalder;Gabrielle; FN:Gabrielle Stalder X-ORCID:https://orcid.org/0000-0002-8901-1181 END:VCARD https://w3id.org/kim/hcrt/scheme https://w3id.org/kim/hcrt/text Textdokument Text LOMv1.0 yes https://creativecommons.org/licenses/by/4.0 application/pdf 1891996 https://phaidra.vetmeduni.ac.at/o:5440 https://phaidra.vetmeduni.ac.at/api/object/o:5440/thumbnail LOMv1.0 discipline