A novel intermediate stage in the transition between short- and long-term facilitation in the sensory to motor neuron synapse of aplysia

Neuron. 1995 Feb;14(2):413-20. doi: 10.1016/0896-6273(95)90297-x.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aplysia
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Evoked Potentials / drug effects
  • Ganglia, Invertebrate / physiology
  • Long-Term Potentiation / drug effects
  • Long-Term Potentiation / physiology*
  • Memory
  • Memory, Short-Term
  • Motor Neurons / physiology*
  • Nerve Tissue Proteins / biosynthesis*
  • Neuronal Plasticity / drug effects
  • Neuronal Plasticity / physiology*
  • Neurons, Afferent / physiology*
  • Serotonin / pharmacology
  • Synapses / physiology*
  • Time Factors


  • Nerve Tissue Proteins
  • Serotonin