Monoamine-containing neurons in the Aplysia brain.

The localization of monoamine-containing neurons in the CNS of Aplysia depilans has been studied by fluorescent histochemistry (the glyoxylic acid condensation method) and microspectrofluorimetry. Yellow fluorescent nerve cells and fibers show the emission maximum at 515-520 nm which corresponds to that of serotonin fluorophore in a model system. Green fluorescent nerve cells have the emission maximum at 485 nm which corresponds to that of catecholamine. Central catecholamine-containing neurons were found in cerebral, buccal, pedal and unpaired abdominal ganglia. The majority of them were revealed in cerebral ganglia (about 40). Serotonin-containing neurons are abundant in cerebral and pedal ganglia. More than 30 serotonin-containing nerve cells were localized in cerebral ganglia. In the right pedal ganglion approximately 100 neurons were revealed; in the left one about 150. In the abdominal ganglion all nerve cells of this chemical type (except one) are located in the right hemiganglion. The results are summarized in corresponding schemes.