A new anesthesia protocol enabling longitudinal lung-function measurements in neonatal rabbits by micro-CT.

Micro-computed tomography (micro-CT) imaging is an emerging technology with many applications in small animals, for example, the study of pulmonary diseases, although clear guidelines and critical mass of evidence are still missing in the preclinical literature. The neonatal rabbit is a valuable model for studying pulmonary development. However, the longitudinal monitoring of lung function by micro-CT can be challenging. Distinctive datasets corresponding to the end-inspiration and end-expiration phases need to be generated and analyzed to derive lung-functional parameters. The quality of CT scans and the reliability of parameters obtained remain highly dependent on the anesthesia protocol used. Three different anesthetic protocols were tested. The combination of dexmedetomidine 0.25 mg/kg injected intraperitoneally followed by 1% isoflurane was found to facilitate CT imaging at 4 and 11 days after birth. Contrarily, isoflurane and ketamine-xylazine were found unsuitable and thus not investigated further. Total lung volumes significantly increased at day 11 compared with baseline in both respiratory phases, whereas lung tissue remained constant. As expected, functional residual capacity, air-to-tissue ratio, and minute ventilation were significantly increased at day 11 in each animal. Those parameters were correlated with inspiratory capacity, compliance, elastance, and resistance of both respiratory system and tissue component, as measured by flexiVent. Lung development was also evaluated by histomorphometric analyses. In conclusion, we have identified a safe and suitable anesthesia protocol for micro-CT imaging in neonatal rabbits. Moreover, the possibility to longitudinally measure lung function in the same subject dramatically reduced the intraexperimental variability.

Alfaxalone and Dexmedetomidine as an Alternative to Gas Anesthesia for Micro-CT Lung Imaging in a Bleomycin-Induced Pulmonary Fibrosis Murine Model.

Micro-CT imaging could be considered a powerful non-invasive tool for accessing pulmonary fibrosis in mice. However, the choice of the anesthesia protocol plays a fundamental role to obtain robust and reproducible data, avoiding misinterpretations of the results. Inhaled anesthesia is commonly used for micro-CT lung imaging, but sometimes the standardization of the protocol may be challenging for routine activities in drug discovery. In this study we used micro-CT to evaluate the effects of two anesthetic protocols, consisting in Alfaxalone and Dexmedetomidine mixture, as injectable agents, and gaseous isoflurane, on vehicle and bleomycin-treated mice. No significant differences were highlighted between the protocols either for lung aeration degrees by micro-CT or histologic analyses in both the controls and bleomycin-treated groups. Our results support Alfaxalone and Dexmedetomidine mixture as a suitable and safe alternative compared to isoflurane for lung imaging. We also concluded that this injectable mixture may be applied for several imaging technologies and on different mice models.