Abstract
The present positron emission tomography (PET) study used 2-deoxy-2[18F]fluoro-D-glucose (FDG) to examine age-related changes in local cerebral metabolic rates for glucose (LCMRglc) in sedated rhesus macaques and vervet monkeys. Nineteen vervet monkeys were scanned in a cross-sectional design, which consisted of three age groups (birth-59 days, 60-179 days, 180 days-adult) that captured the developmental period of greatest synaptic density within the second group. Two rhesus and two vervet monkeys were also examined longitudinally. Subjects were sedated throughout the procedure with a combination of ketamine and midazolam. Longitudinal and cross-sectional analyses of 20 brain regions indicated that LCMRglc were lowest in rhesus and vervet monkeys less than two months of age (about 60% of adult levels). These metabolic rates more than doubled to approximately 155% of adult levels after the second postnatal month, coincident with transient synaptic overproduction and increased sociobehavioral activity. LCMRglc remained high until six months postnatally, coincident with continued dendritic growth and the emerging sociobehavioral independence of the young monkey. After six months, cerebral glucose utilization decreased gradually to adult levels. Thus, the period between 2-6 months is a time of peak metabolic activity, which coincides with increased histologic and behavioral activity in the developing monkey.