The filum terminale of the frog spinal cord, a nontransformed glial preparation: II. Uptake of serotonin.

The uptake of 5-HT was measured in the frog filum terminale (FT), a preparation composed almost exclusively of normal glia. [3H]5-HT was taken up by the FT via a high-affinity, sodium-dependent, temperature-sensitive transport system having a Km of 0.7 microM. In addition, a variety of drugs and aromatic amines known to selectively inhibit 5-HT uptake by synaptosomes and brain slices affected the uptake of 5-HT by the FT in qualitatively similar manner. The FT was shown to accumulate [3H]5-HT at rates significantly greater than the lumbar enlargement which contains both neurons and glia. The glial accumulation of 5-HT by the FT was verified by autoradiography. These findings strongly support the suggestion that glia may modulate aminergic transmission by competing with neurons for the reuptake of neuronally released amines.