Figure 1.

Effect of lithium concentration on inhibition of mouse cortical synaptosomal glutamate uptake. Synaptosomes were prepared from fresh 0.5-mm slices of mouse cerebral cortex by direct Percoll density gradient centrifugation of an S₁ fraction as described in Experimental Procedures. Aliquots of synaptosomes (30 μg) were preincubated for 30 min in 3.2 ml of KHBS with various concentrations of lithium or choline chloride. The suspensions then were adjusted to 5 μM [³H]l-glutamate, uptake stopped after 4 min by rapid filtration and rinsing with 10 ml of fresh buffer, and the radioactivity on the filter counted by liquid scintillation (see Experimental Procedures). Displayed are averages of three separate experiments, each in triplicate ± SE. Significance of differences relative to zero lithium: ∗, P = 0.007; ∗∗, P < 0.001. B is an enlargement of the low lithium portion of A.