Friauf E, Aragón C, Löhrke S, Westenfelder B, Zafra F
Zentrum der Physiologie, University Frankfurt, Med Sch, Theodor-Stern-Kai 7, D-60596 Frankfurt, Germany.
J Comp Neurol. 1999 Sep 13;412(1):17-37.
The synaptic action of many neurotransmitters is terminated by specific transporters that remove the molecules from the synaptic cleft and help to replenish the transmitter supply. Here, we have investigated the spatiotemporal distribution of the glycine transporter GLYT2 in the central auditory system of rats, where glycinergic synapses are abundant. In adult rats, GLYT2 immunoreactivity was found at all relay stations, except the auditory cortex. Many immunoreactive puncta surrounded the neuronal somata in the cochlear nuclear complex, the superior olivary complex, and the nuclei of the lateral lemniscus. In contrast, diffuse neuropil labeling was seen in the inferior colliculus and the medial geniculate body. The punctate perisomatic labeling and the diffuse neuropil labeling were very similar to the staining pattern described previously with glycine antibodies in the auditory system, suggesting that GLYT2 is a reliable marker for glycinergic synapses. However, there was a discrepancy between cytoplasmic GLYT2 and glycine labeling, as not all neuron types previously identified with glycine antibodies displayed somatic GLYT2 immunoreactivity. During development, GLYT2 immunoreactivity appeared between embryonic days 18 and 20, i.e., shortly after the time when the earliest functional synapses have been established in the auditory system. Labeling turned from a diffuse pattern to a clustered, punctate appearance. The development was also characterized by an increase of the signal intensity, which generally lasted until about postnatal day 10. Thereafter, a decrease occurred until about postnatal day 21, when the mature pattern was established in most nuclei. Because of the perinatal onset of GLYT2 immunoreactivity, we speculate that the transporter molecules participate in the process of early synapse maturation.
许多神经递质的突触作用是由特定的转运体终止的，这些转运体将分子从突触间隙中移除，并有助于补充递质供应。在此，我们研究了甘氨酸转运体GLYT2在大鼠中枢听觉系统中的时空分布，该系统中甘氨酸能突触丰富。在成年大鼠中，除听觉皮层外，在所有中继站均发现了GLYT2免疫反应性。在耳蜗核复合体、上橄榄复合体和外侧丘系核中，许多免疫反应性小点围绕着神经元胞体。相比之下，在下丘和内侧膝状体中可见弥漫性神经毡标记。点状的胞体周围标记和弥漫性神经毡标记与先前在听觉系统中用甘氨酸抗体描述的染色模式非常相似，表明GLYT2是甘氨酸能突触的可靠标记。然而，细胞质GLYT2和甘氨酸标记之间存在差异，因为并非所有先前用甘氨酸抗体鉴定的神经元类型都显示出体细胞GLYT2免疫反应性。在发育过程中，GLYT2免疫反应性出现在胚胎第18至20天之间，即在听觉系统中最早的功能性突触建立后不久。标记从弥漫性模式转变为聚集的点状外观。发育过程的特征还包括信号强度增加，这通常持续到出生后第10天左右。此后，信号强度下降，直到出生后第21天左右，此时大多数核中建立了成熟模式。由于GLYT2免疫反应性在围产期开始出现，我们推测转运体分子参与了早期突触成熟过程。
