Memory extinction requires gene expression in rat hippocampus.
Rats with cannulae in the dorsal CA1 region of the hippocampus were trained in one-trial step-down inhibitory avoidance, and submitted to four consecutive daily test sessions without the footshock. This produced extinction of the conditioned response in control animals. The bilateral infusion into the CA1 region of the dorsal hippocampus of two different inhibitors of gene transcription, DRB (80 microg/side) or alpha-amanitin (25 pg/side), or of the protein synthesis inhibitor, anisomycin (80 microg/side) blocked extinction of the CR. The treatments were effective when given 15 min before, but not 1 or 3h after the first test session. Retrieval itself was not affected by the drugs. The treatments did not affect general activity in an open field or anxiety levels measured in an elevated plus maze. The data indicate that gene transcription and protein synthesis are necessary at the time of the first test session in order to generate extinction. These requirements are to be expected from learning that involves new synaptic associations.
Vianna
Monica R
MR
Centro de Memória, Departamento de Bioqui;mica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, 90035-003, RS, Porto Alegre, Brazil. mrmvianna@yahoo.com <mrmvianna@yahoo.com>
Igaz
Lionel Muller
LM
Coitinho
Adriana S
AS
Medina
Jorge H
JH
Izquierdo
Ivan
I
D000546:Amanitins / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D004004:Dichlororibofuranosylbenzimidazole / Q000008:administration & dosage / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005108:Extinction, Psychological; D015870:Gene Expression / Q000187:drug effects*; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar
D000546:Amanitins; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D004004:Dichlororibofuranosylbenzimidazole