Lowndes M, Stewart M G
Biology Department, Open University, Milton Keynes, UK.
Brain Res. 1994 Aug 15;654(1):129-36. doi: 10.1016/0006-8993(94)91578-4.
One to three day old chicks spontaneously peck at small objects. When presented with a chrome bead coated with the bitter tasting substance methyl anthranilate (MeA), chicks peck once, display a characteristic disgust response and subsequently avoid a similar bead. Chicks that are trained on a water coated bead continue to peck a similar bead on retrial. Twenty four hours after training on this one-trial passive avoidance paradigm, chicks were tested for retention. The brains of chicks displaying the correct behavioural response (> 90%) were removed and the lobus parolfactorius from each hemisphere was dissected from the brain and impregnated using a rapid Golgi technique. Analysis of large multipolar neurones by centrifugal dendritic branch order showed that there were significantly more spines on all orders examined in the left hemispheres of MeA-trained chicks compared to water-trained control chicks. Significantly higher spine densities were also found on 4th and 5th order branches of neurones in the right lobus parolfactorius of MeA-trained chicks compared to water-trained chicks. No significant difference in dendritic length was observed. These results suggest that substantial plasticity occurs in post-synaptic structures in the lobus parolfactorius following passive avoidance training. It is suggested that this plasticity is related to processes involved in long term information storage.
1至3日龄的雏鸡会自发地啄食小物体。当给它们呈现一颗涂有苦味物质邻氨基苯甲酸甲酯（MeA）的镀铬珠子时，雏鸡啄一下，表现出一种典型的厌恶反应，随后会避开类似的珠子。在涂有水的珠子上接受训练的雏鸡在再次试验时会继续啄类似的珠子。在这种单次被动回避范式训练24小时后，对雏鸡进行记忆测试。将表现出正确行为反应（>90%）的雏鸡的大脑取出，从每个半球的脑内分离出副嗅叶，并使用快速高尔基技术进行浸染。通过离心树突分支顺序对大型多极神经元进行分析表明，与接受水训练的对照雏鸡相比，接受MeA训练的雏鸡左半球所有检查顺序的树突棘明显更多。与接受水训练的雏鸡相比，接受MeA训练的雏鸡右副嗅叶中神经元的第4和第5级分支上也发现了明显更高的树突棘密度。未观察到树突长度有显著差异。这些结果表明，被动回避训练后，副嗅叶的突触后结构会发生显著的可塑性变化。有人认为这种可塑性与长期信息存储所涉及的过程有关。
