title: Function of insulin in snail brain in associative learning.
abstract: Insulin is well known as a hormone regulating glucose homeostasis across phyla. Although there are insulin-independent mechanisms for glucose uptake in the mammalian brain, which had contributed to a perception of the brain as an insulin-insensitive organ for decades, the finding of insulin and its receptors in the brain revolutionized the concept of insulin signaling in the brain. However, insulin's role in brain functions, such as cognition, attention, and memory, remains unknown. Studies using invertebrates with their open blood-vascular system have the promise of promoting a better understanding of the role played by insulin in mediating/modulating cognitive functions. In this review, the relationship between insulin and its impact on long-term memory (LTM) is discussed particularly in snails. The pond snail Lymnaea stagnalis has the ability to undergo conditioned taste aversion (CTA), that is, it associatively learns and forms LTM not to respond with a feeding response to a food that normally elicits a robust feeding response. We show that molluscan insulin-related peptides are up-regulated in snails exhibiting CTA-LTM and play a key role in the causal neural basis of CTA-LTM. We also survey the relevant literature of the roles played by insulin in learning and memory in other phyla.
authors.affiliation: Department of Structure and Function of Neural Network, Korea Brain Research Institute (KBRI), 61 Cheomdan-ro, Dong-gu, Daegu, 701-300, Korea. satoshikojima.sk@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, 769-2193, Japan. hsunada@kph.bunri-u.ac.jp.
authors.forename: H
authors.initials: H
authors.lastname: Sunada
authors.affiliation: Faculty of Science and Engineering, Tokushima Bunri University, 1314-1 Shido, Sanuki, 769-2193, Japan. kmita@kagawa.bunri-u.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Mita
authors.affiliation: School of High-Technology for Human Welfare, Tokai University, 317 Nishino, Numazu, 410-0321, Japan. manabu@tokai.ac.jp.
authors.forename: M
authors.initials: M
authors.lastname: Sakakibara
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada. lukowiak@ucalgary.ca.
authors.forename: K
authors.initials: K
authors.lastname: Lukowiak
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, 769-2193, Japan. eito@kph.bunri-u.ac.jp.
authors.forename: E
authors.initials: E
authors.lastname: Ito
mesh_terms: D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D061385:Insulins / Q000378:metabolism*; D012908:Snails / Q000502:physiology*
chemical_list: D061385:Insulins
keywords: Conditioned taste aversion; Insulin; Long-term memory; Lymnaea; Synaptic enhancement