Abstract: Crayfish A6 ganglion responses to 520nm monochrome illumination with an increase in discharging frequency, which shows an obvious adaptation after 2min. During the adaptation period the responses to test-illuminations decline. This characteristic response can not be suppressed by extracellular high [Mg²⁺], but be accelerated by it alternatively. Extracellular high [Ca²⁺] can accelerate the adaptation. It seems there is no chemical synapses involved in the adaptation. Extracellular low [Na⁺] can delay the time course of adaptation, and the effect of low [Na⁺] can be diminished by the extracellular high [Ca²⁺]. Also, we did not observe transportation of the characteristic response across hypopharyngeal ganglion. This suggested a central reflex model that was initiated by the photosensitive neuron in crayfish CNS perhaps. Statistics from 239 samples imply a possibility during development course of crayfish: the neuron reserves photosensitive potential to response to illumination; or gradualy eliminates its function in adult stage.

Key words: Procamburus clarkii, A6 ganglion, CPR, photosensitive neuron, adaptation, centrally initiated reflex model, potential of neuron, elimination of function of neuron

摘要： 520nm光照诱发克氏原螯虾尾神经节光敏神经元反应，发现2min后出现明显适应现象。适应期间，用550nm检测光刺激引起的效应随适应发展逐渐减弱。胞外高［Mg²⁺]不抑制此光敏反应；高［Mg²⁺］、高［Ca²⁺］均显著增加适应速率；低［Na⁺］显著降低适应速率，但能被胞外高［Ca²⁺］所拮抗。检测光敏神经元的上行传入通路，未见通过下咽神经节，提示可能有中枢启动运动反射环路。统计239例成体螯虾光敏神经元反应检出率，提示在发育过程中存在作为光感受器的光敏及适应潜能的保留或消亡机制。

关键词: 克氏原螯虾, 腹六节, 光敏神经元, 适应, 中枢启动反射环路, 神经元潜能, 神经元机能消亡