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Learning and Long-term Memory

開催日 2014/9/12
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Taste avoidance conditioning with electrical shock as unconditional stimulus in Lymnaea stagnalis

  • P2-240
  • 滝上 慧 / Satoshi Takigami:1 榊原 学 / Manabu Sakakibara:1 
  • 1:東海大学大学院生物科学研究科生物科学専攻 / Graduate School of Bioscience, Tokai University, Shizuoka, Japan 

New taste avoidance conditioning paradigm has developed with an electrical shock as an unconditional stimuli (US) paired with sucrose application as a conditional stimuli (CS). Our previous study demonstrated that Lymnaea stagnalis can be conditioned with 20 paired presentations of sucrose as CS and gentle tactile stimulus as US. In this study we examined whether snails are capable to be conditioned with 100 mM sucrose application as CS paired with brief electrical stimulus (1000 V, 80 micro-A, 0.2 s) application in place of mechanical tapping to animal's head as US. Snails were evaluated with the feeding score, i.e., the number of mouth openings per minute in response to sole CS application examined at 10 min and/or 24 h following the conditioning paradigm. We defined that a 10 min post-test characterized as a short term memory (STM) whereas a 24 h post-test characterized as a long term memory (LTM). In this study we evaluated the number of CS-US pairings from 5 to 20 whether snails acquired STM/LTM. As a result animals showed significant reduced feeding scores to sucrose application after 15 paired presentations of CS-US pairings leading to both STM and LTM, furthermore their memory persisted for at last one week. We next made intracellular recordings from right pedal dorsal 11 (RPeD11) neuron, which is known to process invasive stimulus such as mechanical tactile and/or chemical stimulus to control the whole-body-withdrawal response which is the only available escape behavior to this animal. Excitatory post synaptic potential was recorded in response to US application thus the electrical voltage stimulus was recognized as the invasive stimulus as same as the mechanical tactile stimulus we previously employed as US. With this new methodology we do not require the skill for the experimenter to give a tactile stimulus.

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