title: An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea.
abstract: Conditioned taste aversion (CTA) in Lymnaea is brought about by pairing a sucrose solution (the conditioned stimulus, CS) with an electric shock (the unconditioned stimulus, US). Following repeated CS-US pairings, CTA occurs and it is consolidated into long-term memory (LTM). The best CTA is achieved, if snails are food-deprived for 1 day before training commences. With a longer period of food deprivation (5 days), learning and memory formation does not occur. It has been hypothesized that the levels of insulin in the central nervous system (CNS) are very important for CTA to occur. To test his hypothesis, we injected insulin directly into 5-day food-deprived snails. The injection of insulin, as expected, resulted in a decrease in hemolymph glucose concentration. Consistent with our hypothesis with insulin injection, learning and memory formation of CTA occurred. That is, the 'insulin spike' is more important than an increase in hemolymph glucose concentration for CTA-LTM. If we injected an insulin receptor antibody into the snails before the insulin injection, learning was formed but memory formation was not, which is consistent with our previous study. Therefore, a rise in the insulin concentration (i.e., insulin spike) in the CNS is considered to be a key determining factor in the process of CTA-LTM.
authors.affiliation: Department of Nano Material and Bio Engineering, Faculty of Science and Engineering, Tokushima Bunri University, Sanuki 769-2193, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Mita
authors.affiliation: Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Yamagishi
authors.affiliation: Department of Systems Neuroscience, School of Medicine, Sapporo Medical University, Sapporo 060-8556, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujito
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
authors.forename: Ken
authors.initials: K
authors.lastname: Lukowiak
authors.affiliation: Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan. Electronic address: eito@kph.bunri-u.ac.jp.
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ito
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects* / Q000502:physiology; D005508:Food Deprivation / Q000502:physiology; D005947:Glucose / Q000032:analysis; D006458:Hemolymph / Q000737:chemistry; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D008195:Lymnaea; D009042:Motivation / Q000187:drug effects / Q000502:physiology; D013649:Taste / Q000502:physiology*
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D005947:Glucose
keywords: Conditioned taste aversion; Deprivation; Glucose; Hemolymph; Insulin; Lymnaea; Motivation; Sucrose