General anesthetics may act as neurotoxins in the developing mammalian nervous system and cause long-term neurobehavioral changes after exposure in infancy. Repeated exposure is particularly deleterious to the developing nervous system, and children who undergo more than one general anesthesia before the age of 4 are at an increased risk for substantial emotional and cognitive changes. It is therefore critical that preventative treatments be found. Studies in animal models have suggested that persistent anesthetic-induced changes such as neurotoxicity, gliotoxicity, loss of synapses and changes in mitochondrial structure may lead to long-term behavioral impairments. Early effects of anesthesia on mitochondria may be key to long-term impairments: protection of mitochondria from oxidative stress caused by free radical generation from general anesthetics eliminates subsequent cognitive impairment in adulthood in rodents. We have established a nonhuman primate model of early anesthetic exposure. In a previous award, we showed that infant rhesus monkeys that received multiple exposures of to the inhalation anesthetic sevoflurane, commonly used in pediatric anesthesia, showed long-term changes in socioemotional and cognitive development when tested later in development. In this new proposal, we will use that model to test the hypothesis that neonatal anesthesia exposure is associated with long-term changes in synaptic and mitochondrial structure in the primate brain, and that protection of mitochondria from oxidative stress at the time of anesthesia exposure mitigates or prevents subsequent changes in cognitive and socioemotional development. Specifically, in Aim 1 of this project, mitochondrial and synaptic structure in adulthood will be examined at the electron microscopic level in tissue prepared and banked from those subjects from the previous award.
For Aim 2, infant rhesus macaques will be exposed to sevoflurane (3 exposures in the six weeks of life) in the presence of R(+)pramipexole, a mitochondrial protectant, or treated with vehicle and will be followed behaviorally for 2 years to assess sparing of neurobehavioral changes in the treated group. We will determine whether R(+)pramipexole treatment also protects against synaptic and mitochondrial changes in these monkeys. Together, results from these studies can provide a causal link between anesthetic exposure, mitochondrial dysfunction, and altered emotional and cognitive behavior in monkeys. They will also provide a first step towards improved anesthetic protocols and preventative treatments that will allow children to undergo safe surgery while minimizing unintended long-term effects on the brain and behavior.
Repeated exposure to the inhalant anesthetic sevoflurane in infancy impacts cognitive and emotional development in rhesus monkey model, which has implications for childhood anesthetic exposure in humans. This project will test whether changes in mitochondrial structure and/or loss of synapses may account for those changes. We will then evaluate whether R(+)pramipexole (a mitochondrial protectant) given prior to anesthesia exposure can prevent the behavioral and neural changes associated with repeated sevoflurane exposure.
