Significant long-term, but not short-term, hippocampal-dependent memory impairment in adult rats exposed to alcohol in early postnatal life

• Published in: Developmental psychobiology Vol. 56; no. 6; pp. 1316 - 1326
• Main Authors: Goodfellow, Molly J., Lindquist, Derick H.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.09.2014
• Subjects: Animals; Association Learning - drug effects; Conditioning (Psychology) - drug effects; context pre-exposure facilitation effect; Electroshock; Ethanol - pharmacology; Fear - drug effects; Female; fetal alcohol spectrum disorder; Freezing Reaction, Cataleptic; hippocampus; Hippocampus - drug effects; Male; memory consolidation; Memory, Long-Term - drug effects; Memory, Short-Term - drug effects; NMDA receptor; Rats; Rats, Long-Evans; fetal alcohol spectrum disorder; context pre-exposure facilitation effect; hippocampus; NMDA receptor; memory consolidation
• ISSN: 0012-1630; 1098-2302; 1098-2302
• DOI: 10.1002/dev.21210

ABSTRACT In rodents, ethanol exposure in early postnatal life is known to induce structural and functional impairments throughout the brain, including the hippocampus. Herein, rat pups were administered one of three ethanol doses over postnatal days (PD) 4–9, a period of brain development comparable to the third trimester of human pregnancy. As adults, control and ethanol rats were trained and tested in a variant of hippocampal‐dependent one‐trial context fear conditioning. In Experiment 1, subjects were placed into a novel context and presented with an immediate footshock (i.e., within ∼8 sec). When re‐exposed to the same context 24 hr later low levels of conditioned freezing were observed. Context pre‐exposure 24 hr prior to the immediate shock reversed the deficit in sham‐intubated and unintubated control rats, enhancing freezing behavior during the context retention test. Even with context pre‐exposure, however, significant dose‐dependent reductions in contextual freezing were seen in ethanol rats. In Experiment 2, the interval between context pre‐exposure and the immediate shock was shortened to 2 hr, in addition to the standard 24 hr. Ethanol rats trained with the 2 hr, but not 24 hr, interval displayed retention test freezing levels roughly equal to controls. Results suggest the ethanol rats can encode a short‐term context memory and associate it with the aversive footshock 2 hr later. In the 24 hr ethanol rats the short‐term context memory is poorly transferred or consolidated into long‐term memory, we propose, impeding the memory's subsequent retrieval and association with shock. © 2014 Wiley Periodicals, Inc. Dev Psychobiol 56: 1316–1326, 2014.