A novel intermediate stage in the transition between short- and long-term facilitation in the sensory to motor neuron synapse of aplysia.
A major difference between short- and long-term memory is that long-term memory is dependent on new protein synthesis. Long-term memory can be further subdivided into a transient, initial phase that is readily susceptible to disruption and a later, more stable and persistent stage. To analyze this transition on the cellular level, we have examined the steps whereby short-term facilitation is converted to a long-term form in the sensorimotor connection of the Aplysia gill-withdrawal reflex. We found that stable long-term facilitation (at 24 hr) requires a higher concentration (100 nM) of serotonin (5-HT) than does short-term facilitation (10 nM). By using low concentrations of 5-HT, which do not produce long-term facilitation, we now have been able to explore the intermediate phases between the short- and long-term processes. By this means we have uncovered a new transient phase that involves three mechanistically different mechanisms--covalent modification, translation, and transcription--each of which can be recruited as a function of the concentration of 5-HT.
Howard Hughes Medical Institute Center for Neurobiology and Behavior, Columbia University, New York, New York 10032.
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M
Ghirardi
P G
PG
Montarolo
E R
ER
Kandel
D000818:Animals; D001048:Aplysia; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects; D017952:Ganglia, Invertebrate / Q000502:physiology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008568:Memory; D008570:Memory, Short-Term; D009046:Motor Neurons / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D013997:Time Factors
D009419:Nerve Tissue Proteins; D012701:Serotonin