MEMORY EXTINCTION REQUIRES GENE EXPRESSION IN RAT HIPPOCAMPUS

VIANNA MR; COITINHO AS; IGAZ LM; MEDINA JH; IZQUIERDO I

Salvador, Bahia, Brasil

Congreso; XVII Reunião Anual da FeSBE; 2002

Federação de Sociedades de Biologia Experimental

Aim:The association of an initially neutral stimulus (CS) with another motivational stimulus (US) leaves long-lasting memories. If the CS is presented alone memory suffers extinction. The aim of this study was to characterize the hippocampal molecular requirements of extinction and to determine if extinction consists in an active plastic process. Méthods and Results:Wistar rats were trained in one-trial step-down inhibitory avoidance, a Pavlovian contextual fear procedure in which the CS is a platform and the US is a footshock. Animals received intrahippocampal infusions of two inhibitors of gene transcription, DRB or a-amanitin, or of the protein synthesis inhibitor, anisomycin, at different periods from training and test sessions. Results: The infusion of DRB or a-amanitin, or anisomycin, 15 min prior to the first test session, blocked extinction. The treatments were ineffective when given 1 or 3 h after that session. Conclusions:The data indicate that gene transcription and protein synthesis are necessary for extinction and endorses the view that extinction implies a new learning. Support: PRONEX ,CNPq ,CONICET