OLFACTORY BULB DEVELOPMENT IN HUMAN FETUSES (AN IMMUNOHISTOCHEMICAL STUDY)

Olfactory bulbs (OB) were studied in human fetuses using immunohistochemistry. Immunohistochemical markers of S-100 and SNAP-25 protein complexes specific to the nervous system, were used in the study. At 20-22 weeks of development, the number of the cells expressing S-100 was greater in the OB than in the neocortical areas studied (gyrus rectus and gyrus orbitalis longitudinalis internus). The quantitative differences detected suggest the heterochronism of the glial differentiation in OB and the cerebral cortex. Immunopositive reaction for SNAP-25 was first detected in the OB peripheral layers and glomeruli in 2022-week human fetuses. On the basis of immunohistochemical reaction of OB with the antibodies against SNAP-25 it may be suggested that the functioning of human olfactory system before developmental weeks 20-22 was impossible. In 28-29 week fetuses, the intensity of immunostaining was different in various topographic areas. The reaction with the antibodies against SNAP-25 in OB of term fetuses was similar to that one in OB of adults. The results of the immunohistochemical study using the reaction that detected SNAP-25 complex in OB of human fetuses suggest that the functioning of human primary olfactory center does not start before the 30 week of prenatal development.

S-100, SNAP-25, olfactory bulbs, immunohistochemistry, S-100, SNAP-25, development