Prenatal development of the rat amygdaloid complex: an electron microscopic study

The prenatal development of the rat amygdaloid complex was studied ultrastructurally day by day starting from the 12th embryonic day (ED12) until birth (ED22). In the earlier stages of embryogenesis, the nerve cells were observed to be of small size. A thin cytoplasmic ring rich in free ribosomes surrounded the oval nuclei. The nucleoli were prominent their number being two or more in a nucleus. The intercellular spaces were wide. A significant advance in the development of the nerve cells and the neuropil was detected in the period between ED15 and ED18. This advance was represented by an increase in the cytoplasmic volume, appearance and development Golgi zones, grouping of the free ribosomes into rosettes, appearance of single synaptic contacts, and a ramification of large-calibre nerve processes that continued during the later stages of the embryogenesis (ED19-ED22). By the end of the prenatal period the number of the synaptic contacts increased and well-developed synaptic apparatuses were observed. The development of the organelles in the perikarya was also advanced. Nissl bodies were found in some neurons. The number of enlarged Golgi zones and mitochondria increased.