High affinity [3H]glutamate uptake systems in normal and audiogenic seizure-susceptible mice.

Two high affinity sodium-dependent and PDC-sensitive glutamate (GLU) uptake systems are present in a whole brain synaptosomal preparation from adult C57BL/10 SPS/SPS normal mice. System 1 has an apparent Km of 3.65 microM while that of System 2 is 46.8 microM. Glutamate uptake in the normal mice increases gradually during development, displaying a striking peak at postnatal day 15, and decreases rapidly between PN 16 and PN 20 until it reaches adult levels. The developmental pattern of GLU uptake System 1 and System 2 in audiogenic seizure susceptible mice is similar to that described in normal mice. However, there are differences between GLU uptake system 1 and 2 during ontogenesis: (1) System 1 could not be detected until PN 15 while being markedly diminished in adulthood; and (2) GLU uptake by System 2 is increased in adults. In addition, the Umax for System 2 is significantly greater than that of normal mice at PN 2 and PN 15.