Journal of Neuroscience, Vol 4, 1994-2000, Copyright © 1984 by Society for Neuroscience
Evidence for FMRF-amide as a neurotransmitter in the gill of Aplysia californica
S Weiss, JI Goldberg, KS Chohan, WK Stell, GI Drummond and K Lukowiak
In Aplysia californica, multiple regulatory mechanisms are involved in the
actions of neurotransmitters on the gill. Neurotransmitter receptors and
adenylate cyclase were examined in a particulate fraction of gill
homogenates. The neuropeptide FMRF-amide stimulated enzyme activity 7- to
8-fold (EC50, 1 microM) via receptors that were pharmacologically distinct
from those for dopamine and serotonin. FMRF- amide augmented cyclic AMP
levels in slices of gill tissue with a time course similar to that for
adenylate cyclase activation. Increases in cyclic AMP levels produced by
the neuropeptide were potentiated by the phosphodiesterase inhibitor
theophylline. Physiological responses to neuropeptides and cyclic AMP
analogues were examined in a perfused, isolated gill preparation. Phasic
contractions evoked by FMRF-amide (EC50, 0.1 microM) were mimicked by
membrane-permeable analogues of cyclic AMP. Comparison of FMRF-amide
effects on adenylate cyclase and gill behavior suggests an association
between cyclic AMP and phasic contractions. In addition, FMRF-amide-like
immunoreactivity, detected by antisera raised against the neuropeptide, was
found in nerve fibers innervating the gill. These findings indicate that in
Aplysia, FMRF- amide or a closely related peptide neurotransmitter may be
involved in the physiological regulation of gill behavior.