Evidence for transient perinatal glutamatergic innervation of globus pallidus

There is no known glutamatergic innervation of globus pallidus (GP) in adult mammals, but we report that during postnatal development of the GP there are large, transient increases in both presynaptic high-affinity glutamate uptake and postsynaptic Na⁺-independent glutamate receptor binding. These glutamatergic markers increase rapidly in rat GP after birth and then decrease to adult levels over a period of weeks. A similar developmental pattern of pallidal glutamate binding was found in human brains. In contrast, binding in rat caudate-putamen (CPu) increases after birth, reaches a peak, and remains constant into adulthood. The results suggest that a glutamatergic pathway transiently innervates the globus pallidus during the perinatal period. Because glutamate is an excitotoxin, this pathway may account, in part, for the basal ganglia damage seen in some forms of cerebral palsy after perinatal hypoxia/ischemia.