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Dose-effect study of the serotonin agonist R-8-OH-DPAT on opioid-induced respiratory depression in blesbok (Damaliscus pygargus philipsi) and impala (Aepyceros melampus)

Pfitzer, S., Laubscher, L., Meyer, L., Warren, K.ORCID: 0000-0002-9328-2013, Vaughan-Higgins, R.ORCID: 0000-0001-7609-9818, Raath, J.P. and Laurence, M.ORCID: 0000-0003-1215-2848 (2019) Dose-effect study of the serotonin agonist R-8-OH-DPAT on opioid-induced respiratory depression in blesbok (Damaliscus pygargus philipsi) and impala (Aepyceros melampus). Veterinary Anaesthesia and Analgesia, 46 (6). pp. 796-806.

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This study aimed to determine whether the R-enantiomer of 8-hydroxy-2-(di-n-propylamino) tetralin (R-8-OH-DPAT) alleviates respiratory depression in antelope species immobilised with etorphine. The experiment also aimed to establish the most clinically effective dose of this serotonin 5- HT1A receptor agonist.

Six female blesbok and six female impala.

Study design
Each animal was subjected to four immobilisation treatments in a prospective four-way crossover design. One control treatment consisting of only etorphine at 0.09 mg kg-1 and three treatments consisting of etorphine at 0.09 mg kg-1 combined with 0.005, 0.02 and 0.07 mg kg-1 of R-8-OH-DPAT, respectively. Induction, quality of immobilisation and recovery were monitored in each treatment. Physiological variables including heart rate, respiratory rate, arterial blood pressure and blood gases, were measured over a time period of 35 minutes during immobilisation. A linear mixed model was used to assess the effects of treatments over the period of recumbence.

R-8-OH-DPAT did not influence induction, immobilisation or recovery scores. Respiratory rate in blesbok was increased in the medium and high dosage R-8-OH-DPAT treatment group. However, this increased respiratory rate did not translate into improvements of arterial partial pressure of oxygen (PaO2) values in the blesbok.

The medium and higher dosages of R-8-OH-DPAT in impala led to an improved PaO2 as well as to decreased opioid-induced tachycardia during the first ten minutes of immobilisation.

and clinical relevance Previous reports indicated that the racemic mixture of 8-OH-DPAT injected intravenously had a positive effect on blood gas values in etorphine-treated hypoxaemic goats. In this experiment, similar effects could be seen in impala at the higher dosage rates of R-8-OH-DPAT. However, failure to achieve an improvement of blood gas values in blesbok was an unexpected result. It could be speculated that the dosage, species-specific differences of serotonin receptors or the use of the R-enantiomer of 8-OH-DPAT might play a role.

Item Type: Journal Article
Murdoch Affiliation: School of Veterinary and Life Sciences
Publisher: Elsevier Ltd.
Copyright: © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia
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