Dynamics of induction and expression of long-term synaptic facilitation in Aplysia

Juliane Mauelshagen, Gretchen R. Parker, Thomas J. Carew

Research output: Contribution to journalArticlepeer-review


Serotonin (5HT)-induced short-term facilitation and long-term facilitation (STF and LTF) of the monosynaptic connection between tail sensory neurons (SNs) and motor neurons (MNs) in Aplysia have been useful in delineating possible cellular mechanisms contributing to short-term and long- term memory. Previous work from our laboratory showed that LTF can be produced in the absence of STF, suggesting that these processes may be functionally independent. In the present study, we explored this hypothesis by examining the temporal relationship between STF and LTF. We recorded intracellularly from pairs of monosynaptically connected SNs and MNs in isolated pleural-pedal ganglia. In the first experimental series, we followed the time course of LTF across a 24 hr period after its induction by five applications of 10 μM 5HT. STF completely decayed to baseline several hours before the expression of LTF. This biphasic expression profile of STF and LTF further supports the hypothesis that LTF is not a simple elaboration of STF. In the second experimental series, we monitored the immediate expression of facilitation during and after different numbers of 5HT applications. We identified a rapidly decaying STF (lasting 15-30 min) after one to four pulses of 50 μM 5HT and a unique, prolonged intermediate-term facilitation (ITF; lasting up to 90 min) after five pulses of 50 μM 5HT. These results raise the possibility that STF, ITF, and LTF may reflect components of different memory phases in the intact animal.

Original languageEnglish (US)
Pages (from-to)7099-7108
Number of pages10
JournalJournal of Neuroscience
Issue number22
StatePublished - Nov 15 1996


  • Aplysia
  • long-term facilitation
  • memory expression
  • memory induction
  • memory phases
  • sensory neurons
  • serotonin
  • short-term facilitation
  • time course

ASJC Scopus subject areas

  • General Neuroscience


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