[Topography of the catecholamine neurons in the brain stem of the human fetus: an immunohistochemical study using antibodies to tyrosine hydroxylase].

Immunohistochemistry using antibodies to tyrosine hydroxylase (TH), a rate-limiting enzyme which catalyzes the initial step in the catecholamine synthesizing pathway, has been widely accepted as one of the methods for identification of catecholamine neurons in the nervous system. In the present study, we performed immunohistochemical examination to elucidate the distribution of catecholamine neurons in brain stem of human fetuses. The brain stems were obtained from 8 human fetuses (CRL: 120-275 mm, GA: 15-27 wks) 1-3 h after death following therapeutic or spontaneous abortion. They were immediately fixed with 4% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4, dehydrated with graded ethanol, and embedded in paraffin. Serial 6 microns sections were cut from 7 different levels of the brain stem of each fetus. These sections were stained by peroxidase-antiperoxidase (PAP) technique using TH antisera. The TH antisera used were raised in rabbits by injecting purified TH from bovine adrenal medulla. The preparation and the specificity of TH antisera were described in detail elsewhere (Nakashima et al, 1983). Catecholamine neurons were clearly demonstrated in the brain stem of all fetuses. They could be recognized as catecholamine cell groups in the same manner as is done in experimental mammals. Among these cell groups, the catecholamine neurons showed distinct cytological features in shape and size. The distribution of catecholamine positive neurons in the brain stem was almost the same in the 8 human fetuses, and an atlas was given with anatomical explanation under the terminology of Olszewski and Baxter (1982) for the human brain stem. In the mesencephalon, a large number of catecholamine neurons lay in the nucleus substantiae nigrae, pars compacta, the nucleus paranigralis, the middle of the ventral tegmentum and the tractus tegmentalis centralis, and fewer catecholamine neurons were scattered in the other tegmental area. In addition, a group of small catecholamine neurons was located in the griseum centrale mesencephali near the aqueduct. In the pons, catecholamine neurons occurred mainly in the nucleus locus coeruleus and the nucleus subcoeruleus. A band of TH-positive neurons extended from the nucleus locus coeruleus to the dorsolateral tegmentum, and further to the roof of the fourth ventricle. Occasional catecholamine neurons were present in the area medial to the upper portion of the nucleus locus coeruleus. More caudally, a small number of catecholamine neurons were scattered in the area medial to the nervus facialis and adjacent to the nucleus facialis and the nucleus olivaris superior.(ABSTRACT TRUNCATED AT 400 WORDS)