Increase in number of functional release sites by cyclic AMP-dependent protein kinase in cultured neurons isolated from hippocampal dentate gyrus.
The enhancement of synaptic exocytosis is one form of long-term potentiation (LTP) of synaptic transmission. As possible mechanisms underlying this enhancement, increases in the release probability and/or the number of release sites are suggested. To obtain direct evidence for the increase in the number of functional release sites induced by protein kinase A (PKA) cascade, we attempted to visualize functional release sites using styryl dyes, FM4-64 and FM1-43, and investigated the effects of PKA on the release sites. A PKA activator FSK increased the number of active release sites by approximately 20-30%. A direct PKA activator, Sp-cAMPS, showed the same effect, which was blocked by a PKA inhibitor, KT5720, suggesting that this effect was mediated by PKA. This PKA-dependent increase in the number of release sites requires Ca(2+) in the bath solution, and Sr(2+) can not be a substitute for Ca(2+). Since the number of functional release sites is approximately half the total number of synaptophysin-immunoreactive sites, the PKA dependent activation of silent release sites of DG neuron terminals is suggested.
Kohara
K
K
Laboratory for Memory and Learning, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, 351-0198, Saitama, Japan. kohara@nphys.med.osaka-u.ac.jp
Ogura
A
A
Akagawa
K
K
Yamaguchi
K
K
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002227:Carbazoles; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D018891:Dentate Gyrus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013324:Strontium / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology
D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D018377:Neurotransmitter Agents; D011758:Pyrroles; D013873:Thionucleotides; D005576:Colforsin; C016957:adenosine-3',5'-cyclic phosphorothioate; C057416:KT 5720; D011189:Potassium Chloride; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium; D013324:Strontium