title: Involvement of insulin-like peptide in long-term synaptic plasticity and long-term memory of the pond snail Lymnaea stagnalis.
abstract: The pond snail Lymnaea stagnalis is capable of learning taste aversion and consolidating this learning into long-term memory (LTM) that is called conditioned taste aversion (CTA). Previous studies showed that some molluscan insulin-related peptides (MIPs) were upregulated in snails exhibiting CTA. We thus hypothesized that MIPs play an important role in neurons underlying the CTA-LTM consolidation process. To examine this hypothesis, we first observed the distribution of MIP II, a major peptide of MIPs, and MIP receptor and determined the amounts of their mRNAs in the CNS. MIP II was only observed in the light green cells in the cerebral ganglia, but the MIP receptor was distributed throughout the entire CNS, including the buccal ganglia. Next, when we applied exogenous mammalian insulin, secretions from MIP-containing cells or partially purified MIPs, to the isolated CNS, we observed a long-term change in synaptic efficacy (i.e., enhancement) of the synaptic connection between the cerebral giant cell (a key interneuron for CTA) and the B1 motor neuron (a buccal motor neuron). This synaptic enhancement was blocked by application of an insulin receptor antibody to the isolated CNS. Finally, injection of the insulin receptor antibody into the snail before CTA training, while not blocking the acquisition of taste aversion learning, blocked the memory consolidation process; thus, LTM was not observed. These data suggest that MIPs trigger changes in synaptic connectivity that may be correlated with the consolidation of taste aversion learning into CTA-LTM in the Lymnaea CNS.
authors.affiliation: Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki 769-2193, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Murakami
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Okada
authors.forename: Hisayo
authors.initials: H
authors.lastname: Sadamoto
authors.forename: Suguru
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Koichi
authors.initials: K
authors.lastname: Mita
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Miki
authors.initials: M
authors.lastname: Yamagishi
authors.forename: Dai
authors.initials: D
authors.lastname: Hatakeyama
authors.forename: Emi
authors.initials: E
authors.lastname: Otsuka
authors.forename: Akiko
authors.initials: A
authors.lastname: Okuta
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sunada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takigami
authors.forename: Manabu
authors.initials: M
authors.lastname: Sakakibara
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujito
authors.forename: Masahiko
authors.initials: M
authors.lastname: Awaji
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Moriyama
authors.forename: Ken
authors.initials: K
authors.lastname: Lukowiak
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; D007328:Insulin / Q000494:pharmacology; D008195:Lymnaea / Q000187:drug effects / Q000502:physiology*; D057567:Memory, Long-Term / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D013649:Taste / Q000187:drug effects / Q000502:physiology
chemical_list: D007328:Insulin; D009479:Neuropeptides; C063879:insulin-related neuropeptide