Changing distribution patterns of synaptophysin-immunoreactive structures in the human dorsal striatum of the fetal brain

Within the striatum two compartments, matrix and patches, can be distinguis hed by differences in the expression of neuroactive substances, afferent an d efferent connections and time of neurogenesis. The present study was done to demonstrate the pattern of synaptophysin (SYN) expression which is indi cative of synaptogenesis in the human fetal striatum (15th-32nd weeks of ge station) with special reference to developmental changes. From the 15th to the 22nd gestational weeks an intense diffuse SYN immunolabelling of striat al patches is observed. In the matrix SYN-immunoreactive fiber bundles are seen until the 20th week. Thereafter, the matrix is nearly devoid of SUN-im munoreactive structures. From the 28th week of gestation the matrix contain s diffuse SYN immunoreactive which gradually becomes as intense as that of the patches. The latter, thus, can no longer be delineated in the 30th week . The results show that fibrous SYN immunolabelling most probably indicatin g intra-axonal transport of synaptic vesicles can only be observed during t he first half of gestation. Moreover, it becomes obvious that the patch com partment can selectively be visualized by anti-SYN until the 28th week. Thi s pattern may correspond to the, early dopaminergic innervation from the su bstantia nigra which is known to roach the developing patches. From the 28t h week a transition from patchy to diffuse immunolabelling is seen. The inc rease in matrix labelling may be due to the occurrence of new neuronal cont acts. The changeover from patchy to homogeneous SYN immunolabelling takes p lace distinctly earlier than changes in the distribution of other neuroacti ve substances described before. Anat Rec 258:198-209, 2000. (C) 2000 Wiley- Liss, Inc.