猫下丘中央核GABA能神经元年龄相关变化

AGE-RELATED CHANGES OF GABA-ERGIC NEURONS IN THE CENTRAL NUCLEUS OF CAT INFERIOR COLLICULUS

目的比较研究猫下丘中央核(CIC)GABA能神经元年龄相关变化,探索老年个体听力下降的神经机制。方法Nissl染色显示下丘神经元,免疫组织化学ABC法显示γ-氨基丁酸(GABA)免疫阳性神经元。光镜下观察、拍照,对神经元和GABA能神经元分别计数并换算成密度,测量GABA能神经元直径取平均值。结果GABA阳性反应神经元、阳性纤维及其终末在青年猫及老年猫下丘中央核均有分布。与青年猫相比,老年猫下丘中央核神经元及GABA能神经元密度均显著下降(P<0.01),GABA能神经元下降幅度较大;GABA能神经元胞体直径明显减小(P<0.01),阳性反应明显减弱。结论在衰老过程中猫下丘神经元尤其是GABA能神经元有显著丢失现象,提示GABA能神经元显著减少导致下丘兴奋性和抑制性神经递质之间的平衡失调,可能是引起老年个体听觉功能衰退的重要原因。

Objective To camparatively investgate age-related changes of GABAergic neurons in the inferior colliculus of young adult and old cats, and to discuss the neural mechanism of auditory degeneration during senescence underlying these changes. Methods Nissl staining was used to display all the inferior colliculus neurons, and immunohistochemical method was introduced to exhibit the GABAergic neurons. Under the microscope, the number of the GABAergic neurons was counted and their diameter measured. Results The GABA immunoreactive cells, the fibers and their teminals were distributed widely in central neuclei of inferior colliculus in young and old cats. The density of the total neurons, especially of the GABAergic neurons, declined significantly in the old cats when compared with that of the young adults. The GABAergic neurons in old cats decreased in body size （P〈0. 01）, with shortened positive fibres and decreased immunoreaction of GABA. The diameter, density, and number of GABAergic neurons in old cats declined significantly in comparison with those of the young adults （P〈0. 01）. Conclusion An evident loss of neurons, especially GABAergic neurons, in old inferior colliculus may result in an imbalance of excitement and inhibition, which might be an important reason for the auditory degeneration in senescence.