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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)

Involvement of mACh receptor on contextual eyeblink conditioning in mice

  • P2-244
  • ラフマン ムハマドアシュラフ / Md.ashrafur Rahman:1 臼井 弘児 / Kouji Usui:1,2 川原 茂敬 / Shigenori Kawahara:1,2 
  • 1:富山大学 / Grad. Sch. Innovative Life Science, Univ. Toyama 2:富山大工生命工学 / Dpt. Life Sciences and Bioengineering, Fac. Engineering, Univ. Toyama 

For better understanding of the neural mechanism that underlies development of context-based differential responses to the same stimulus, utilization of the classical eyeblink conditioning will provide salient information, because its basic input-output pathways have been studied well. We used a delay paradigm consisting of a 350-ms tone conditioned stimulus (CS) and a 100-ms periorbital electrical shock unconditioned stimulus (US) with an interstimulus interval of 250 ms. A 2-s light was delivered as a contextual cue before the CS in CS-US paired trials (cued trial) while no preceding cue was delivered in CS alone trials (noncued trial). The interval between the contextual cue and the CS was randomized between 5 and 6 s, resulting in a 3-4 s of stimulus free interval between the conditional cue offset and the CS onset. The sequence of the cued and noncued trial was randomized and intertrial interval was set between 60 and 70 s. Male C57BL/6 mice (8-10 weeks old) received scopolamine (1.0 mg/kg, i.p.) 20 min before the daily conditioning started (scopolamine group, n=8), whereas control mice (n=8) received saline. We found that control mice progressively acquired the conditioned response to the CS in cued trials but not in noncued trials, showing the context-dependent differential response to the same tone. On the contrary, the scopolamine group acquired the conditioned response both in cued and noncued trials, suggesting an impairment in relating the preceding light cue to the following CS-US association while CS-US association itself was not disturbed. This was consistent with the absence of effect of scopolamine on the expression of the pre-acquired discriminating ability. Control mice having reached an asymptotic level showed the context-dependent differential response even after receiving scopolamine injection. These results suggest that activation of mACh receptors may be involved in convoluting the context cue to the associative memory, but not in sensory processing, motor outputs, nor cognition of the context itself.

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