Survival anesthetic and injection procedures for neonatal opossums

The laboratory opossum, Monodelphis domestica, differs from most other marsupial species in that females lack a pouch, and neonates are exposed. This characteristic has fostered the use of this species for research on normal developmental processes early in life and on experimental perturbations of those processes. However, in vivo experiments on neonates younger than 5 days old have been hampered by lack of a protocol that is efficient in anesthetizing the mother without causing loss of the litter. Therefore, the enormous potential for exploring this prototype laboratory marsupial in research on biological features of the neonatal stages is largely undeveloped. We report here that halothane inhalation through a 50-ml conical tube placed over the mother's head succeeded in rapidly inducing anesthesia of the mother while sparing the babies from contact with the anesthetic. Babies 0 to 2 days old survived injections of saline while their mothers were anesthetized by this procedure. This anesthetic procedure enables broad use of neonatal opossums as models for biomedical research on early developmental processes of mammals.