title: Apelin-13 Impaires Acquisition but Not Consolidation or Expression of Contextual Fear in Rats.
abstract: Apelin-13, as an endogenous neuropeptide, is the ligand for the G-protein-coupled receptor, APJ, which has recently been demonstrated to be involved in the process that contributes to learning and memory. Previous studies showed that apelin may be required for certain forms of learning and memory. Up to date, the role of apelin in fear memory has not been explored. In the present study, we tested the effects of apelin-13 (1.0, 2.0 and 4.0 µg/rat) on contextual fear conditioning (experiment 1), consolidation (experiment 2) and expression (experiment 3) in rats. A well established fear conditioning protocol was used, which contained three training phases: habituation, fear conditioning and test. Apelin-13 was i.c.v injected 10 min before conditioning (experiment 1), immediately after conditioning (experiment 2) or 10 min before testing (experiment 3). The values of percent freezing were used to measure fear. We found that only 2.0 µg apelin-13 administrations produced a decrease freezing in experiment 1. The most effective dose of apelin-13 (2.0 µg) was selected, but it had no effect on freezing in experiment 2 and 3. Furthermore, the decreased freezing in experiment 1 was not attributed to the deficits of locomotor activity and foot-shock sensitivity. These results, for the first time, indicated that apelin-13 impaired fear acquisition but not fear consolidation or expression.
authors.affiliation: Department of Physiology, School of Basic Medical Science, Central South University, Changsha, 410007, Hunan, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Han
authors.affiliation: Department of Physiology, School of Basic Medical Science, Central South University, Changsha, 410007, Hunan, People's Republic of China.|Department of Anatomy, Histology and Embryology, Changsha Medical University, Changsha, 410219, Hunan, People's Republic of China.
authors.forename: Huaiqing
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, 410013, Hunan, People's Republic of China.
authors.forename: Fulian
authors.initials: F
authors.lastname: Huang
authors.affiliation: Department of Physiology, College of Medicine, University of South China, Hengyang, 421001, Hunan, People's Republic of China. tsw1997@126.com.
authors.forename: Shaowen
authors.initials: S
authors.lastname: Tian
authors.affiliation: Department of Physiology, School of Basic Medical Science, Central South University, Changsha, 410007, Hunan, People's Republic of China. shishikong_1998@163.com.
authors.forename: Xiaoqun
authors.initials: X
authors.lastname: Qin
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D005239:Fear / Q000187:drug effects*; D036341:Intercellular Signaling Peptides and Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D008124:Locomotion / Q000187:drug effects; D008297:Male; D008568:Memory / Q000187:drug effects*; D017207:Rats, Sprague-Dawley
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; C495199:apelin-13 peptide
keywords: Apelin-13; Fear conditioning; Fear consolidation; Fear expression; Rats