Dynamic changes in cerebral glucose metabolism in conscious infant monkeys during the first year of life as measured by positron emission tomography

Abstract

Recently, advances in spatial resolution have provided the opportunity to utilize positron emission tomography (PET) to examine local cerebral metabolic rates for glucose (lCMR glc) in large animals noninvasively, thereby allowing repeated lCMR glc measurements in the same animal. Previous studies have attempted to describe the ontogeny of cerebral glucose metabolism in anesthetized nonhuman primates using [ 18 F ]fluorodeoxyglucose (FDG) and PET. However, the use of sedation during the tracer uptake period may influence lCMR glc. This study was conducted to describe lCMR glc in conscious infant vervet monkeys ( Cercopithecus aethiops sabaeus) during the first year of life utilizing FDG–PET. Cross-sectional studies ( n=23) displayed lowest and highest lCMR glc in all structures at the 2–3 and 8–9 month age groups, respectively. The metabolic pattern suggested an increase in lCMR glc values between 2 and 8 months of age with decreased metabolism observed at 10–12 months of age in all regions. Peak lCMR glc values at 8 months were an average of 84±24% higher than values seen at the youngest age examined quantitatively (2–3 months). The regions of greatest and smallest increases in lCMR glc at 8 months were the cerebellar hemispheres (90%) and the thalamus (39%), respectively. Longitudinal analysis in 4 animals supported this developmental pattern, demonstrating the ability to detect changes in cerebral glucose metabolism within animals and the potential for FDG–PET in nonhuman primate models of brain maturation. By determining the normative profile of lCMR glc during development in monkeys, future application of FDG–PET will provide the opportunity to longitudinally assess the effects of environmental or pharmacological intervention on the immature brain.