采用放射自显影技术测定脑切片胆碱能Ｍ型受体，观察大鼠在老年早期和老年晚期不同脑区Ｍ型受体密度的变化。结果：所得脑切片自显影像灰度层次清晰，主要分布在皮质、海马、纹状体等部位，非特异结合灰度很低。图像分析仪分别给出不同脑区的平均灰度值，老年鼠皮质、海马、纹状体的灰度显著低于青年鼠，老年早期大鼠３个脑区分别降低２４８７％，１４１２％，１２７６％（Ｐ＜００５）；老年晚期分别降低２９４５％，２４３３％，１５３１％（Ｐ＜００５）。结论：老年大鼠大脑皮质、海马、纹状体部位胆碱能Ｍ型受体密度显著降低，老年晚期比老年早期降低的幅度更大 The cholinergic M-type receptors in brain sections were determined by autoradiography. The changes of M-type receptor density in different brain regions in early and old aged rats were observed. Results: The self-developed images of brain slices were clearly grayscale, mainly distributed in the cortex, hippocampus and striatum. The non-specific binding gray was low. The gray values ​​of cortex, hippocampus and striatum of aged rats were significantly lower than those of young mice, respectively. The brain regions of the aged rats were reduced by 2487% and 14 respectively 12% and 1276%, respectively (P <005). The late elderly patients decreased by 2945%, 2433% and 1531% respectively (P <005). CONCLUSION: The density of cholinergic M-type receptors in cerebral cortex, hippocampus and striatum of senile rats is significantly lower than that in the early part of the elderly