Down-regulation of protein kinase C and kinase inhibitors dissociate short- and long-term enhancement produced by one-trial conditioning of Hermissenda

J Neurophysiol. 1993 Feb;69(2):636-41. doi: 10.1152/jn.1993.69.2.636.


1. The visual system of Hermissenda has been studied extensively as a site of cellular plasticity produced by classical conditioning. Previous research has shown that one-trial conditioning, consisting of light paired with serotonin (5-HT) results in short- and long-term enhancement of light-elicited generator potentials in identified type B-photoreceptors. Recent evidence suggests that 5-HT exerts its effects on the induction of short-term enhancement by activation of protein kinase C (PKC), a Ca(2+)-activated and phospholipid-dependent protein kinase. However, the contribution of protein kinases in general, and specifically PKC in long-term enhancement has not been established. 2. The protein kinase inhibitors H-7 and sphingosine blocked the induction of short-term enhancement when applied before one-trial conditioning. However, the conditions that are sufficient to block the induction of short-term enhancement do not block long-term enhancement. Sphingosine and H-7 do not block the induction and expression of long-term enhancement when applied before one-trial conditioning. 3. Pretreatment before conditioning with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), which leads to down-regulation of PKC, also did not block long-term enhancement. Down-regulation by itself did not produce enhancement, although the transient peak of light-elicited generator potentials was reduced by pretreatment with TPA. 4. The results suggest that the induction of short- and long-term enhancement involve parallel processes, and thus the expression of long-term cellular plasticity produced by one-trial conditioning does not depend on the induction or expression of short-term enhancement.

Publication types

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

MeSH terms

  • 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
  • Animals
  • Brachyura / physiology*
  • Conditioning, Classical / physiology*
  • Down-Regulation / drug effects*
  • Isoquinolines / pharmacology
  • Neuronal Plasticity / drug effects
  • Photic Stimulation
  • Photoreceptor Cells / physiology
  • Piperazines / pharmacology
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Serotonin / pharmacology
  • Sphingosine / pharmacology
  • Tetradecanoylphorbol Acetate / pharmacology


  • Isoquinolines
  • Piperazines
  • Serotonin
  • 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
  • Protein Kinase C
  • Sphingosine
  • Tetradecanoylphorbol Acetate