title: Modulatory effect of ionizing radiation on food-NaCl associative learning: the role of gamma subunit of G protein in Caenorhabditis elegans.
abstract: Ionizing radiation (IR) is known to impair learning by suppressing adult neurogenesis in the hippocampus. However, in a mature nervous system, IR-induced functional alterations that are independent of neurogenesis remain largely unknown. In the present study, we analyzed the effects of IR on a food-NaCl associative learning paradigm of adult Caenorhabditis elegans that does not undergo neurogenesis. We observed that a decrease in chemotaxis toward NaCl occurs only after combined starvation and exposure to NaCl. Exposure to IR induced an additional decrease in chemotaxis immediately after an acute dose in the transition stage of the food-NaCl associative learning. Strikingly, chronic irradiation induced negative chemotaxis in the exposed animals, i.e., the primary avoidance response. IR-induced additional decreases in chemotaxis after acute and chronic irradiation were significantly suppressed in the gpc-1 mutant, which was defective in GPC-1 (one of the two gamma subunits of the heterotrimeric G-protein). Chemotaxis to cAMP, but not to lysine and benzaldehyde, was influenced by IR during the food-NaCl associative learning. Our novel findings suggest that IR behaves as a modulator in the food-NaCl associative learning via C. elegans GPC-1 and a specific neuronal network and may shed light on the modulatory effect of IR on learning.
authors.affiliation: Microbeam Radiation Biology Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki, Gunma 370-1292, Japan. sakashita.tetsuya@jaea.go.jp
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sakashita
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Hamada
authors.forename: Daisuke D
authors.initials: DD
authors.lastname: Ikeda
authors.forename: Sumino
authors.initials: S
authors.lastname: Yanase
authors.forename: Michiyo
authors.initials: M
authors.lastname: Suzuki
authors.forename: Naoaki
authors.initials: N
authors.lastname: Ishii
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D001245:Association Learning / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D001547:Benzaldehydes / Q000494:pharmacology; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D029742:Caenorhabditis elegans Proteins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000528:radiation effects; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005502:Food; D044388:GTP-Binding Protein gamma Subunits / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D005720:Gamma Rays; D008239:Lysine / Q000494:pharmacology; D009154:Mutation; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D001547:Benzaldehydes; D029742:Caenorhabditis elegans Proteins; D044388:GTP-Binding Protein gamma Subunits; C454139:gpc-1 protein, C elegans; D012965:Sodium Chloride; D000242:Cyclic AMP; D008239:Lysine; C032175:benzaldehyde