Serotonin induces temporally and mechanistically distinct phases of persistent PKA activity in Aplysia sensory neurons

Neuron. 1998 Dec;21(6):1423-34. doi: 10.1016/s0896-6273(00)80660-1.


The cAMP signaling cascade has been implicated in several stages of memory formation. We have examined activation of this cascade by serotonin (5-HT) in the sensory neurons of Aplysia. We find that different patterns of 5-HT exposure induce three distinct modes of PKA activation. First, a single 5 min pulse induces transient (5 min) PKA activation that requires neither transcription nor translation. Second, 4-5 pulses induce intermediate-term persistent activation (3 hr duration) that requires translation but not transcription. Third, 5 pulses of 5-HT, as well as continuous (90 min) exposure, induce long-term persistent activation 20 hr later, which requires both transcription and translation. Thus, in the sensory neurons, different patterns of 5-HT give rise to three independent phases of PKA activation that differ in their induction requirements, their temporal profiles, and their molecular mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aplysia
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / genetics*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Enzyme Activation
  • Ganglia, Invertebrate / physiology*
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / physiology*
  • In Vitro Techniques
  • Kinetics
  • Memory / physiology
  • Neurons, Afferent / drug effects
  • Neurons, Afferent / enzymology
  • Neurons, Afferent / physiology*
  • Phosphorylation
  • Protein Biosynthesis
  • Serotonin / pharmacology*
  • Signal Transduction / physiology
  • Time Factors
  • Transcription, Genetic


  • Serotonin
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases