Cellular accumulation of amines and amino acids in the central ganglia of a gastropod mollusc, Planorbis corneus: an autoradiographic study.

The distribution of radioactivity was examined autoradiographically in ganglia exposed to 10 different tritium-labelled compounds, some putative transmitters and the others transmitter precursors. The autoradiographic pattern was found to vary greatly for different substances, suggesting the presence of several different accumulating systems in the ganglia. Identified amine-containing neurons take up their own transmitter substance specifically. However, whereas uptake by dopamine-containing, and presumed histamine-containing neurons occurs over both perikarya and processes, in 5-HT-containing neurons it appears restricted to axon processes. The transmitter precursors L-DOPA and 5-hydroxytryptophan were taken up by the perikarya of both dopamine- and 5-HT-containing neurons, possibly by the same uptake system. In high concentrations, tyramine was selectively accumulated by cells containing dopamine and by non-dopamine (possibly octopamine- or tyramine-containing) neurons, but in low concentrations it labelled only the latter. GABA labelled a separate population of neurons and was particularly concentrated in their processes. Some, if not all, of the neurons specifically labelled after exposure to glutamic acid are neurosecretory cells. Tyrosine and glycine appeared to be accumulated in a non-specific manner and many of the substances were also accumulated by glial cells or by parts of the connective tissue capsule.