Fluorescence histochemical and ultrastructural studies of locus coeruleus of human fetal brain

Catecholamine (CA) containing neurons and processes of the putative locus coeruleus (LC) of human fetal brain have been identified by the use of a modified Falck-Hillarp fluorescence histochemical technique and have been examined by light and electron microscopy. Fetuses were received as surgical specimens following abortion by hysterotomy. Estimated gestational ages varied between 11 and 18 weeks. Small granular vesicles (SGV) ranging from 450 to 650 A and large granular vesicles (LGV) ranging from 700 to 1050 A were identified in variable numbers along with agranular vesicles in the cell bodies and processes of neurons in the LC of all fetal specimens examined by electron microscopy. The occurrence of SGV in association with green fluorescence within the LC of a 12-week-old human fetus suggests a relatively early ontogenetic development of a storage mechanism for CA within this nucleus.