Nussbaumer J C, Wall P D
Brain Res. 1985 Dec 23;360(1-2):1-9. doi: 10.1016/0006-8993(85)91213-2.
A possible role fore peripheral unmyelinated fibres on the establishment and maintenance of stable receptive fields mediated by myelinated afferents has been studied in the mouse cortical barrelfield. The barrels are cytoarchitectonic units consituting a visible and particularly precise somatotopic map of the facial vibrissae. Barrelfields were mapped electrophysiologically in adults using two experimental setups: (i) after destruction of unmyelinated peripheral fibres by systemic administration of capsaicin neonatally; and (ii) after inactivation of these fibres by local application of capsaicin to the nerve subserving the vibrissae in the adult. The latter procedure is known not to destroy fibres. Control animals received the vehicle used to dissolve capsaicin. The effectiveness of capsaicin on the peripheral fibres was assessed histochemically on their terminals in the substantia gelatinosa. Both methods of application of capsaicin resulted in a large expansion of cortical receptive fields: units within a particular barrel were driven by a statistically significant, larger number of vibrissae than in controls. No morphological alterations of the barrels were found in cortical tangential sections. We concluded that capsaicin treatment 'defocusses' the normal physiological precision without destroying the general plan of representation and without alteration of the barrel pattern.
在小鼠大脑皮层桶状区，研究了外周无髓鞘纤维在由有髓鞘传入纤维介导的稳定感受野的建立和维持中可能发挥的作用。桶状区是细胞构筑单位，构成了面部触须可见且特别精确的躯体感觉定位图。使用两种实验装置对成年小鼠的桶状区进行电生理图谱绘制：（i）在新生小鼠通过全身注射辣椒素破坏无髓鞘外周纤维后；（ii）在成年小鼠通过向支配触须的神经局部应用辣椒素使这些纤维失活后。已知后一种方法不会破坏纤维。对照动物接受用于溶解辣椒素的赋形剂。通过对其在脊髓胶状质中的终末进行组织化学评估辣椒素对外周纤维的作用效果。两种应用辣椒素的方法均导致皮层感受野大幅扩大：与对照相比，特定桶状区内的神经元由数量显著更多的触须驱动。在皮层切线切片中未发现桶状区有形态学改变。我们得出结论，辣椒素处理使正常生理精度“失焦”，但不破坏表征的总体布局，也不改变桶状区模式。
