Journal of Neuroscience, Vol 8, 3507-3514, Copyright © 1988 by Society for Neuroscience
Fast axonal transport of modulatory neuropeptides from central ganglia to components of the feeding system in Aplysia
PE Lloyd
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
The transport of neuropeptides from central ganglia to components of the
feeding system was studied in Aplysia. Peptide transport was determined by
incubating buccal or cerebral ganglia with 35S-methionine and measuring the
appearance of labeled peptides by high-pressure liquid chromatography
(HPLC) of extracts of target tissues. Selected nerves were left intact and
passed through a Vaseline diffusion barrier separating the ganglia and
their targets. Five major labeled peptides were observed to be transported
from the buccal ganglia to feeding muscles. They were buccalin, FMRFamide,
myomodulin, and 2 small cardioactive peptides. Each of these peptides has
been shown to modulate the responses of these muscles to their motor
neurons. The peptides were transported by fast axonal transport, as judged
by the distance transported and the sensitivity to colchicine. When
normalized to correct for differences in total incorporation, the patterns
of peptide transport were reproducible between animals. The nature and
amount of the peptides transported were different for different muscles.
The nature of peptide transport also varied for different nerve groups.
These results support the proposition that these 5 peptides act as
modulatory transmitters at feeding muscles. No transport of neuropeptides
from the cerebral ganglia to feeding muscles was observed, although
myomodulin was specifically transported to the buccal ganglia. This
suggests that this peptide may play an important role in the previously
observed regulation of buccal ganglia activity by neurons in the cerebral
ganglia.