title: Nucleus incertus inactivation impairs spatial learning and memory in rats.
abstract: Nucleus incertus (NI) is a pontine nucleus which releases mainly GABA and relaxin-3 in rats. Its suggested functions include response to stress, arousal, and modulation of hippocampal theta rhythm. Since the role of NI in learning and memory has not been well characterized, therefore the involvement of this nucleus in spatial learning and memory and the aftermath hippocampal levels of c-fos and pCREB were evaluated. NI was targeted by implanting cannula in male rats. For reference memory, NI was inactivated by lidocaine (0.4 μl, 4%) at three stages of acquisition, consolidation and retrieval in Morris water maze paradigm. For working memory, NI was inactivated in acquisition and retrieval phases. Injection of lidocaine prior to the first training session of reference memory significantly increased the distance moved, suggesting that inactivation of NI delays acquisition in this spatial task. Inactivation also interfered with the retrieval phase of spatial reference memory, as the time in target quadrant for lidocaine group was less, and the escape latency was higher compared to the control group. However, no difference was observed in the consolidation phase. In the working memory task, with inter-trial intervals of 75 min, the escape latency was higher when NI was inactivated in the retrieval phase. In addition, c-fos and pCREB/CREB levels decreased in NI-inhibited rats. This study suggests that nucleus incertus might participate in acquisition of spatial reference, and retrieval of both spatial reference and working memory. Further studies should investigate possible roles of NI in the hippocampal plasticity.
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Nategh
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurobiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Nikseresht
authors.affiliation: Neurobiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Fariba
authors.initials: F
authors.lastname: Khodagholi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Electronic address: motamedi@ams.ac.ir.
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Motamedi
mesh_terms: D000779:Anesthetics, Local / Q000633:toxicity; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism; D007859:Learning Disabilities / Q000139:chemically induced / Q000503:physiopathology*; D008012:Lidocaine / Q000633:toxicity; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D011939:Mental Recall / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D065853:Spatial Learning / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D016760:Proto-Oncogene Proteins c-fos; D008012:Lidocaine
keywords: Morris water maze; Nucleus incertus; Reversible inactivation; Spatial memory