乙酰胆碱对家鸽(Columba livia)顶盖脑片中Ⅲ层神经元电活动的影响

The Effects of ACh upon the Layer Ⅲ Neurons in Pigeon (Columba livia) Optic Tectum Slices

实验在２２只家鸽的离体顶盖脑片上，用玻璃微电极胞外记录到顶盖Ⅲ层神经元自发放电单位５０个，观察了乙酰胆碱（ａｃｅｔｙｌｃｈｏｌｉｎｅ，ＡＣｈ）及其拮抗剂以及电刺激Ⅱａ－ｆ亚层对Ⅲ层神经元电活动的作用。结果显示，脑片灌流ＡＣｈ（１０－６ｍｏｌ／Ｌ，３ｍｉｎ）后，２４／３７个单位（６４．９％）放电频率增加。４／３７个单位（１０．８％）放电频率降低，７／３７个单位（１８．９％）无明显变化，另２／３７个单位表现为先增频后减频反应。２４个被ＡＣｈ增频的单位，其中１５个单位（占６２．５％）的增频作用可被１０－６ｍｏｌ／Ｌ阿托品（ａｔｒｏｐｉｎｅ，ＡＴＲ）部分或完全阻断，其余９个单位（占３７．５％）的增频作用则不受影响。１３个被Ⅱａ－ｆ亚层刺激传入增频的Ⅲ层神经元，其中１０个单位（占７６．９％）的增频效应可被ＡＴＲ逆转，另３个单位的阻断效果则不明显。上述药物的作用具有可逆性和重复性。实验表明：家鸽顶盖Ⅲ层中可能有胆碱能纤维的到达，Ⅲ层内存在ＡＣｈ敏感神经元。顶盖Ⅱａ－ｆ亚层与Ⅲ层神经元间的兴奋性突触传递递质可能为ＡＣｈ，且在兴奋性传递过程中有Ｍ型受体参与。

spontaneous discharging units were recorded extracellularly in the layer Ⅲ of 22 pigeons optic tectum slices by glass micropitettes.The effects of putative transmitter,acetylcholine(ACh),and its antagonist perfused and electric stimulating sublayer Ⅱ a f on the layer Ⅲ neurons were investigated.The results were as follows:Most of layer Ⅲ neurons(24/37,64.9%) were excited by ACh(10 -6 mol/L,3 min),only a small portion of cells showed inhibition or were unaffected,and the other two cells showed inhibition after excitation,15 out of 24 units excited by ACh could be blocked partly or completely by atropine (ATR,10 -6 mol/L).The increasing effects of the remaining 9 units couldnt be affected by ATR.The increasing effects of 10 out of the 13 layer Ⅲ units (76.9%) increased by stimulating sublayer Ⅱ a f could be blocked by ATR,but the increasing effects of the other 3 units were not blocked. These results show that there are cholinergic fibres afferenting to pigeon optic tectum layer Ⅲ.There are ACh sensitive neurons in layer Ⅲ.ACh may act as the excitatory transmitter through muscarine receptor action between sublayer Ⅱ a f and layer Ⅲ neurons.