PRENATAL DIFFERENTIATION OF MONOAMINE-CONTAINING NEURONS IN THE LOCUS COERULEUS OF THE RABBIT: A HISTOFLUORESCENCE STUDY

Abstract

The time of appearance and increase of catecholamine fluorescence in the locus coeruleus (LC) of the rabbit fetus (from the 12th to 27th day of gestation) were studied by using the Falck-Hillarp method. No catecholamine fluorescence was detected in the brain of the 12th and 13th days on gestation. On the 15th day, catecholamine fluorescence could be found in the LC neurons. Thereafter the number of these neurons and the intensity of fluorescence in each was increasing gradually. On the 19th day, fluorescent fibers could be discerned in the neuropil extending rostrally from this nucleus. On the 27th day, the most intense fluorescence was observed in the neurons of all present specimens and many fluorescent fibers with varicosities were found in the neuropil.
It is concluded that histofluorescence becomes recognizable in the LC one day later than in both the substantia nigra and cell groups of A1-A3, that catecholamine synthesis in LC neurons may have started in the early fetal life such as on the 15th day of gestation, and that these neurons may store a significant amount of catecholamine before birth.