Erythrosin B is a member of a class of fluorescein dyes that are sug-gested to elicit hyperkinesis when ingested by susceptible children. We found that erythrosin B inhibits dopamine uptake in rat caudate synaptosomes "uncompetilively" in the 10- to 800-micromolar range. Half maximal inhibition of uptake occurred at 45 micromolar. Uncompetitive inhibition denotes a decrease in efficacy of the dopamine membrane transport mechanism with an increase in affinity of dopa-mine to the carrier. Erythrosin B also decreased nonsaturable binding of dopamine to the synaptosome membrane. The inhibitory action of erythrosin B on dopamine uptake is consistent with the hypothesis that erythrosin B can act as a central ex citatory agent able to induce hyperkinetic behavior.
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