Persistent alteration in behavioural reactivity to a mild social stressor in rhesus monkeys repeatedly exposed to sevoflurane in infancy

Background: Socio-emotional development is the expression and management of emotions, which in non-human primates can be examined using responses toward increasing levels of threat. Damage to the limbic system alters socio-emotional development in primates. Thus, neuronal and glial cell loss caused by exposure to general anaesthesia early in infancy might also impact socio-emotional development. We recently reported that repeated sevoflurane exposure in the first month of life alters emotional behaviours at 6 months of age and impairs visual recognition memory after the first year of life in rhesus monkeys. The present study evaluated socio-emotional behaviour at 1 and 2 yr of age in those same monkeys to determine the persistence of altered emotional behaviour. Methods: Rhesus monkeys of both sexes were exposed to sevoflurane anaesthesia three times for 4 h each time in the first 6 weeks of life. At 1 and 2 yr of age, they were tested on the human intruder task, a well-established mild acute social stressor. Results: Monkeys exposed to sevoflurane as infants exhibited normal fear and hostile responses, but exaggerated self-directed (displacement) behaviours, a general indicator of stress and anxiety in non-human primates. Conclusions: Early repeated sevoflurane exposure in infant non-human primates results in an anxious phenotype that was first detected at 6 months, and persists for at least 2 yr of age. This is the first demonstration of such a prolonged impact of early anaesthesia exposure on emotional reactivity.