Otsuka Emi, Matsunaga Miho, Okada Ryuichi, Yamagishi Miki, Okuta Akiko, Lukowiak Ken, Ito Etsuro
Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa 769-2193, Japan.
Cellular and Structural Physiology Institute, Nagoya University, Nagoya, Aichi 464-8601, Japan.
Biophysics (Nagoya-shi). 2013 Nov 13;9:161-6. doi: 10.2142/biophysics.9.161. eCollection 2013.
Conditioned taste aversion (CTA) can be classically conditioned in the pond snail Lymnaea stagnalis and subsequently be consolidated into long-term memory (LTM). The neural trace that subserves CTA-LTM can be summarized as follows: A polysynaptic inhibitory postsynaptic potential recorded in the neuron 1 medial (N1M) cell in the conditioned snails as a result of activation of the cerebral giant cell (CGC) is larger and lasts longer than that in control snails. The N1M cell is ultimately activated by the CGC via the neuron 3 tonic (N3t) cell. That is, the inhibitory monosynaptic inputs from the N3t cell to the N1M cell are facilitated. The N1M and N3t cells are the members of feeding central pattern generator, whereas the CGC is a multimodal interneuron thought to play a key role in feeding behavior. Here we examined the involvement of a second messenger, cAMP, in the establishment of the memory trace. We injected cAMP into the CGC and monitored the potentials of the B3 motor neuron activated by the CGC. B3 activity is used as an index for the synaptic inputs from the N3t cell to the N1M cell. We found that the B3 potentials were transiently enlarged. Thus, when the cAMP concentration is increased in the CGC by taste aversion training, cAMP-induced changes may play a key role in the establishment of a memory trace in the N3t cell.
条件性味觉厌恶（CTA）可在椎实螺（Lymnaea stagnalis）中通过经典条件作用形成，随后巩固为长期记忆（LTM）。支持CTA-LTM的神经痕迹可总结如下：由于脑巨细胞（CGC）的激活，在经过条件作用的蜗牛的神经元1内侧（N1M）细胞中记录到的多突触抑制性突触后电位比对照蜗牛中的更大且持续时间更长。N1M细胞最终由CGC通过神经元3紧张性（N3t）细胞激活。也就是说，从N3t细胞到N1M细胞的抑制性单突触输入得到增强。N1M和N3t细胞是摄食中枢模式发生器的成员，而CGC是一种多模式中间神经元，被认为在摄食行为中起关键作用。在这里，我们研究了第二信使环磷酸腺苷（cAMP）在记忆痕迹形成中的作用。我们将cAMP注入CGC，并监测由CGC激活的B3运动神经元的电位。B3活动用作从N3t细胞到N1M细胞的突触输入的指标。我们发现B3电位短暂增大。因此，当通过味觉厌恶训练使CGC中的cAMP浓度增加时，cAMP诱导的变化可能在N3t细胞中记忆痕迹的形成中起关键作用。
