title: Glucocorticoid-induced enhancement of contextual fear memory consolidation in rats: Involvement of D1 receptor activity of hippocampal area CA1.
abstract: This study investigated the role of dopamine (DA) receptors in area CA1 of the hippocampus in modulating the effects of glucocorticoids on the contextual fear memory consolidation. Adult male rats were given systemic injections of corticosterone (CORT; 3mg/kg) immediately after training in a contextual fear conditioning (CFC) task and the percentage of time spent freezing in the CFC context was recorded 24h after training. Intra-CA1 infusion of the DA type 1 (D1) receptor antagonist SCH 23390 (SCH; 30ng/0.5µl per side) immediately after CORT injection attenuated CORT-induced enhancement of memory consolidation. However, intra-CA1 infusion of the DA type 2 (D2) receptor antagonist sulpiride (SUL; 60ng/0.5µl per side) was ineffective. Neither antagonist alone altered freezing behavior in the 24h CFC retention test. Furthermore, the memory enhancing dose of CORT used in these experiments reduced D1, but not D2, receptor mRNA expression in area CA1. Neither D1 nor D2 antagonism in area CA1 affected total locomotor activity. These findings provide evidence for the involvement of hippocampal D1 receptor activity in area CA1 in CORT-induced enhancement of contextual fear memory consolidation.
authors.affiliation: Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-Sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, PR China. liaoying2010@gmail.com
authors.forename: Ying
authors.initials: Y
authors.lastname: Liao
authors.forename: Yan-Wei
authors.initials: YW
authors.lastname: Shi
authors.forename: Qiu-Ling
authors.initials: QL
authors.lastname: Liu
authors.forename: Hu
authors.initials: H
authors.lastname: Zhao
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D056547:CA1 Region, Hippocampal / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical; D003345:Corticosterone / Q000494:pharmacology; D005239:Fear; D005938:Glucocorticoids / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D005938:Glucocorticoids; D017447:Receptors, Dopamine D1; D003345:Corticosterone
keywords: CFC; CORT; Contextual fear conditioning; Corticosteroid; Corticosterone; DA; Dopamine; Dopamine receptors; Hippocampal CA1; Medial prefrontal cortex; Memory consolidation; PCR; Polymerase chain reaction; SCH; SCH 23390; SUL; Sulpiride; VTA; Ventral tegmental area; mPFC