title: Exogenous insulin-like growth factor 2 administration enhances memory consolidation and persistence in a time-dependent manner.
abstract: Memory consolidation is an important process for the formation of long-term memory. We have previously reported that mature brain-derived neurotrophic factor enhances memory consolidation within 9h after initial learning. Recent studies suggest that insulin-like growth factor 2 (IGF2) significantly enhances memory consolidation and prevents forgetting. Thus, we hypothesized that IGF2 exerts its activity on cognitive performance in a time-dependent manner as observed in our previous study. In the one-trial step-through inhibitory avoidance task, we demonstrate that a bilateral injection of IGF2 into the dorsal hippocampus 6 or 9 h after training significantly enhanced the step-through latencies compared with the vehicle-treated controls in the retention trial, which was conducted 24 h after the acquisition trial. However, 12h post-training, IGF2 injection did not increase the step-through latencies. Intriguingly, in the retention trial at 21 days after the training, hippocampal IGF2 injection 6, 9 or 12 h after the acquisition trial significantly increased the step-through latencies compared with the vehicle-treated controls. IGF2 administration at 9 h and 12 h after the acquisition trial significantly increased discrimination index and exploration time on the novel-located object in the test trial at 24 h and 21 days, respectively, after the acquisition trial in the novel location recognition task. In addition, IGF2-induced an increase in the step-through latencies in the retention trial 24 h or 21 days, respectively, after the initial learning was completely abolished by co-injected anti-IGF2 receptor antibody. These results suggest that IGF2 enhances memory consolidation within 9h after initial learning, and increased IGF2 within the 12 h after the acquisition trial, which represents a delayed consolidation phase, is also critical for memory persistence.
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
authors.forename: Younghwan
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
authors.forename: Young Woo
authors.initials: YW
authors.lastname: Lee
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
authors.forename: Qingtao
authors.initials: Q
authors.lastname: Gao
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
authors.forename: Younghwa
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
authors.forename: Hyung Eun
authors.initials: HE
authors.lastname: Lee
authors.affiliation: Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Department of Oriental Pharmaceutical Science, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea; Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea. Electronic address: jhryu63@khu.ac.kr.
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Ryu
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D004192:Discrimination, Psychological / Q000187:drug effects / Q000502:physiology; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000008:administration & dosage*; D008297:Male; D000069077:Memory Consolidation / Q000187:drug effects* / Q000502:physiology; D008813:Mice, Inbred ICR; D009483:Neuropsychological Tests; D018697:Nootropic Agents / Q000008:administration & dosage*; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage*; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: C513121:IGF2 protein, mouse; D018697:Nootropic Agents; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; D007335:Insulin-Like Growth Factor II
keywords: Insulin-like growth factor 2; Memory consolidation; Memory persistence