Ding S L, Elberger A J
Department of Anatomy and Neurobiology, University of Tennessee, Memphis.
Anat Embryol (Berl). 1994 Jul;190(1):55-63. doi: 10.1007/BF00185846.
Many immunocytochemical studies have identified different types of neurotransmitters localized in the corpus callosum (CC) axons in the adult mammal. Few studies have looked at the development of different neurochemically identified CC systems. Previous studies on the development of cat CC axons have indicated that a large number of transitory CC axons project to the cortex during early postnatal development. The present study focuses on the development of one neurochemically identified group of CC axons in the cat, labeled with an antibody against neuropeptide Y (NPY), to determine if this group participates in transitory CC axonal growth. Cats at specified ages from birth to adulthood were studied with a routine method of immunocytochemistry for antiserum to NPY. NPY-immunoreactive (ir) CC axons were detected at all stages examined, from newborn to adult; the peak density occurred during postnatal weeks (PNW) 3-4. During PNW 1-2, the density of NPY-ir CC axons increased gradually; some NPY-ir axons at this age had growth cones located within the CC bundle between the cerebral hemispheres. The density of the NPY-ir CC axons decreased gradually during PNW 5-7, and from PNW 8 to maturity only a few NPY-ir CC axons were observed. These results indicate that at least two types of NPY-ir CC axons (i.e., transitory and permanent) exist during development, and that most of these axons are eliminated or only express NPY-ir for a short period during development. The results also indicate that neurochemical subsets of CC axons participate in the extensive transitory growth observed by means of the membrane tracer DiI but they may follow unique developmental timetables.
许多免疫细胞化学研究已经确定，成年哺乳动物胼胝体（CC）轴突中存在不同类型的神经递质。很少有研究关注不同神经化学鉴定的CC系统的发育。先前关于猫CC轴突发育的研究表明，在出生后早期发育过程中，大量短暂性CC轴突投射到皮层。本研究聚焦于猫中一组经神经化学鉴定的CC轴突的发育，用抗神经肽Y（NPY）抗体标记，以确定该组轴突是否参与短暂性CC轴突生长。采用针对NPY抗血清的常规免疫细胞化学方法，对从出生到成年的特定年龄段的猫进行研究。在从新生到成年的所有检查阶段都检测到了NPY免疫反应性（ir）CC轴突；峰值密度出现在出生后第3 - 4周。在出生后第1 - 2周，NPY - ir CC轴突的密度逐渐增加；这个年龄段的一些NPY - ir轴突在大脑半球之间的CC束内有生长锥。在出生后第5 - 7周，NPY - ir CC轴突的密度逐渐降低，从出生后第8周直到成熟，仅观察到少数NPY - ir CC轴突。这些结果表明，在发育过程中至少存在两种类型的NPY - ir CC轴突（即短暂性和永久性），并且这些轴突中的大多数在发育过程中被消除或仅在短时间内表达NPY - ir。结果还表明，CC轴突的神经化学亚群参与了通过膜示踪剂DiI观察到的广泛的短暂性生长，但它们可能遵循独特的发育时间表。
