Long-term heterosynaptic inhibition in Aplysia.
Synaptic transmission between mechanosensory and motor neurons of the gill withdrawal reflex in Aplysia can undergo both short-term and long-term modulation. One form of short-term synaptic depression lasting minutes can be evoked by the peptide Phe-Met-Arg-Phe-amide (FMRFamide), and is mediated by the lipoxygenase pathway of arachidonic acid. We report here using cell culture, that the same monosynaptic sensory-to-motor component of the gill withdrawal reflex can also undergo long-term synaptic depression lasting 24 h after five applications of FMRFamide over a 2-h period. The long-term depression evoked by FMRFamide is transmitter-specific. Dopamine or low-frequency stimulation of sensory neurons, which also produce short-lasting synaptic depression in vivo, failed to evoke a long-term change. As is the case for long-term presynaptic facilitation of this connection with serotonin, the long-term depression, but not the short-term, can be blocked when applications of FMRFamide are given in the presence of anisomycin, a reversible inhibitor of protein synthesis. Thus, heterosynaptic depression parallels heterosynaptic facilitation in having a long-term as well as a short-term form, and in both cases the long-term modulation requires the synthesis of gene products not essential for the short-term changes.
Montarolo
P G
PG
Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, New York.
Kandel
E R
ER
Schacher
S
S
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001048:Aplysia; D019835:FMRFamide; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*
D009479:Neuropeptides; D019835:FMRFamide; D000841:Anisomycin