Araki M, Nagayama T
Division of Biological Sciences, Graduate School of Science, Hokkaido University, 060 Sapporo, Japan.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2003 Oct;189(10):731-9. doi: 10.1007/s00359-003-0456-5. Epub 2003 Sep 9.
The neural mechanism of habituation of the crayfish lateral giant-mediated escape reaction was analyzed electrophysiologically and pharmacologically. Upon repeated stimulation of tailfan afferents (at 0.2-1 Hz) lateral giant showed rapid habituation and failed to spike. Upon low-intensity sensory stimulation, the lateral giant responded with two subthreshold excitatory post-synaptic potentials, the alpha and beta components. A third component, the alpha' component, was discriminated at the boundary of excitatory post-synaptic potentials between the late alpha and early beta components with stimulation just subthreshold or suprathreshold to evoke lateral giant spikes. This alpha' component increased in amplitude with hyperpolarizing current injected into the lateral giants, although the amplitude of both the alpha and beta components remained constant. Furthermore, bath application of the nicotinic antagonist, d-tubocurarine caused a rapid reduction in the amplitude of the alpha' component while the amplitude of the beta component was reduced gradually and that of the alpha component remained unchanged. Single-hair stimulation indicated that some sensory afferents made direct connections with the lateral giants mediated by chemical synapses and form the potential of alpha' component of the lateral giants. Since lateral giant inactivation was associated with a reduction of excitatory post-synaptic potential amplitude of the alpha' component, connection from these afferents could contribute, at least in part, to lateral giant habituation.
通过电生理学和药理学方法分析了小龙虾外侧巨神经元介导的逃避反应的习惯化神经机制。在反复刺激尾扇传入神经（频率为0.2 - 1赫兹）时，外侧巨神经元表现出快速习惯化且不再产生动作电位。在低强度感觉刺激下，外侧巨神经元会产生两个阈下兴奋性突触后电位，即α和β成分。第三个成分，α'成分，是在刚好低于阈刺激或阈上刺激以诱发外侧巨神经元动作电位时，在晚期α成分和早期β成分的兴奋性突触后电位边界处区分出来的。尽管α和β成分的幅度保持不变，但当向外侧巨神经元注入超极化电流时，α'成分的幅度会增加。此外，浴槽中应用烟碱拮抗剂d - 筒箭毒碱会使α'成分的幅度迅速降低，而β成分的幅度逐渐降低，α成分的幅度保持不变。单根刚毛刺激表明，一些感觉传入神经通过化学突触与外侧巨神经元直接相连，并形成外侧巨神经元α'成分的电位。由于外侧巨神经元失活与α'成分兴奋性突触后电位幅度的降低有关，这些传入神经的连接至少在一定程度上可能导致外侧巨神经元的习惯化。
