DISTRIBUTION IN THE CENTRAL-NERVOUS-SYSTEM OF APLYSIA OF AFFERENT-FIBERS ARISING FROM CELL-BODIES LOCATED IN THE PERIPHERY

The present study used autoradiography to determine the location of th e projections of presumptive peripheral afferent neurons into the cent ral nervous system of Aplysia. Selected peripheral tissues (with an em phasis on structures involved in feeding behavior) were exposed to rad ioactive amino acids, and the distribution of macromolecules transport ed into the nervous system via afferent fibers was determined by autor adiography. Different regions of the body exhibited different patterns of projections, and, within the neuropil of the cerebral ganglion, th ere was a loose topographical organization of projections from the hea d. For some regions of the body, the projection was largely limited to the ganglion from which the nerve enters; for other regions, the proj ection was very widespread. In some cases (e.g., rhinophore to eye), t here was evidence of projections from one peripheral structure to anot her. Experiments with all peripheral tissues that were studied resulte d in extensive labeling of central ganglia, indicating that afferents with peripheral cell bodies may provide a major source of sensory inpu t to the central nervous system and suggesting that many or all of the numerous ultrafine axons visualized via electron microscopy in the ne rves of Aplysia may originate from first- or second-order sensory affe rents whose cell bodies are located in the periphery. (C) 1995 Wiley-L iss, Inc.