The similarities and diversities of signal pathways leading to consolidation of conditioning and consolidation of extinction of fear memory.
It is generally believed that consolidation of long-term memory requires activation of protein kinases, transcription of genes, and new protein synthesis. However, little is known about the signal cascades involved in the extinction of memory, which occurs when the conditioned stimulus is no longer followed by the unconditioned stimulus. Here, we show for the first time that an intra-amygdala injection of transcription inhibitor actinomycin D at the dose that blocked acquisition failed to affect extinction of a learned response. Conversely, protein synthesis inhibitor anisomycin blocked both acquisition and extinction. Extinction training-induced expression of calcineurin was blocked by anisomycin but not by actinomycin D. NMDA receptor antagonist, phosphatidylinositol 3-kinase (PI-3 kinase), and MAP kinase inhibitors that blocked the acquisition also blocked the extinction of conditioned fear. Likewise, PI-3 kinase inhibitor blocked fear training-induced cAMP response element-binding protein (CREB) phosphorylation as well as extinction training-induced decrease in CREB phosphorylation, the latter of which was associated with calcineurin expression and could be reversed by a specific calcineurin inhibitor. Thus, molecular processes that underlie long-term behavioral changes after acquisition and extinction share some common mechanisms and also display different characteristics.
Lin
Chih-Hung
CH
Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan 701.
Yeh
Shiu-Hwa
SH
Lu
Hsin-Yi
HY
Gean
Po-Wu
PW
D000161:Acoustic Stimulation; D000679:Amygdala / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001923:Brain Chemistry / Q000187:drug effects; D019703:Calcineurin / Q000378:metabolism; D002467:Cell Nucleus / Q000737:chemistry; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000187:drug effects / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004597:Electroshock; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000502:physiology*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D003609:Dactinomycin; D000841:Anisomycin; D019703:Calcineurin