Journal of Neuroscience, Vol 12, 1616-1627, Copyright © 1992 by Society for Neuroscience
Identified FMRFamide-immunoreactive neuron LPL16 in the left pleural ganglion of Aplysia produces presynaptic inhibition of siphon sensory neurons
SA Small, TE Cohen, ER Kandel and RD Hawkins
Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, New York 10032.
The gill- and siphon-withdrawal reflex of Aplysia undergoes transient
inhibition following noxious stimuli such as tail shock. This behavioral
inhibition appears to be due in part to transient presynaptic inhibition of
the siphon sensory cells, which can be mimicked by application of the
peptide FMRFamide. Although FMRFamide is widespread in the Aplysia nervous
system, an FMRFamide-containing inhibitory neuron has not previously been
identified. We have searched for such a neuron by combining FMRFamide
immunofluorescence with fluorescent dye backfilling from the abdominal
ganglion, the location of the siphon sensory cells. These methods localized
a neuron in the left pleural ganglion, which we have named LPL16. LPL16 is
FMRFamide immunoreactive; it is excited by tail shock; and stimulation of
LPL16 produces inhibition of siphon sensory cell-to-motor cell postsynaptic
potentials and narrowing of action potentials in the sensory cells in
tetraethylammonium solution. These results indicate that LPL16 participates
in the inhibitory effects of tail shock, and support the idea that
FMRFamide plays a physiological role in the inhibition.