Down-regulation of protein kinase C and kinase inhibitors dissociate short- and long-term enhancement produced by one-trial conditioning of Hermissenda.
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.
Crow
T
T
Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77225.
Forrester
J
J
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D003386:Brachyura / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D015536:Down-Regulation / Q000187:drug effects*; D007546:Isoquinolines / Q000494:pharmacology; D009473:Neuronal Plasticity / Q000187:drug effects; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D013110:Sphingosine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007546:Isoquinolines; D010879:Piperazines; D012701:Serotonin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate