AUTHOR=Perkas O. , Schmidt A. , Kuehnel C. , Greiser J. , Hermeyer H. , Klingner C. , Freesmeyer M. , Winkens T. 

TITLE=Different narcotic gases and concentrations for immobilization of ostrich embryos for in-ovo imaging

JOURNAL=Experimental Biology and Medicine

VOLUME=Volume 249 - 2024

YEAR=2024

URL=https://www.ebm-journal.org/journals/experimental-biology-and-medicine/articles/10.3389/ebm.2024.10037

DOI=10.3389/ebm.2024.10037

ISSN=1535-3699

ABSTRACT=In-ovo imaging using avian eggs has been described as a potential alternative to common animal testing using rodents. However, imaging studies are hampered by embryonal motion producing artifacts. This study aims at systematically comparing isoflurane, desflurane and sevoflurane in three different concentrations in ostrich embryos. Biomagnetic signals of ostrich embryos were recorded analyzing cardiac action and motion. Ten groups comprising eight ostrich embryos each were investigated: Control, isoflurane (2%, 4%, 6%), desflurane (6%, 12%, 18%) and sevoflurane (3%, 5%, 8%). Each ostrich egg was exposed to the same narcotic gas and concentration on development day (DD) 31 and 34. Narcotic gas exposure was upheld for 90 minutes and embryos were monitored for additional 75 minutes. Toxicity was evaluated by verifying embryo viability 24 hours after the experiments. Initial Hheart rate of mean 148 beats/min (DD 31) and 136 beats/min (DD 34) decreased over time by 44 to 48 beats/minute. No significant differences were observed between groups. All narcotic gases led to distinct movement reduction after mean 8 minutes. Embryos exposed to desflurane 6% with lowest concentration showed residual movements. Highest concentration of Iisoflurane 6% and sevoflurane 8% produced motion-free time intervals of mean 70 minutes after discontinuation of narcotic gas exposure. Only one embryo death occurred after narcotic gas exposure with desflurane 6%.  This study shows that isoflurane, desflurane and sevoflurane are suitable for ostrich embryo immobilization, which is a prerequisite for motion-artifact free imaging. Application of isoflurane 6% and sevoflurane 8% is a) safe as no embryonal deaths occurred after exposure and b) effective as immobilization was observed for approx. 70 minutes after the end of narcotic gas exposure. These results should be interpreted with caution regarding transferability to other avian species as differences in embryo size and incubation duration exist.