Histochemical studies on the distribution of some enzymes concerned with carbohydrate metabolism in the locus ceruleus, nucleus tractus mesencephalicus n. trigemini, nucleus dorsalis n. vagi and nucleus n. hypoglossi of the rat.

Detailed histochemical studies have been conducted on the distribution of hexokinase, amylophosphorylase, aldolase, lactic dehydrogenase, succinic dehydrogenase and glucose-6-phosphate dehydrogenase in every component of the locus ceruleus, nucleus tractus mesencephalicus n. trigemini, nucleus dorsalis n. vagi and nucleus n. hypoglossi of the wistar strain rats. The locus ceruleus and nucleus dorsalis n. vagi which are considered to be belong to "exceptional nuclei" showed mild activity in the nerve cell bodies and strong activity in the surrounding glia cell for the hexokinase reaction. But, the nucleus tractus mesencephalicus n. trigemini and nucleus n. hypoglossi considered to be "usual nuclei" revealed strong activity in the nerve cell bodies and glia cells for the hexokinase reaction, however, glia cells did not show the tendency to surround the nerve cells in these nuclei. On the basis of the present findings, the glia cells may get their energy source from glucose in the circulating blood, and they may be energy donators to the nerve cells in the "exceptional nuclei" whereas the nerve cells may get their energy source directly from glucose in the circulating blood in the "usual nuclei". The former 2 nuclei showed low level activity of succinic dehydrogenase. These findings may indicate that the locus ceruleus and nucleus dorsalis n. vagi belong to the conception "exceptional nuclei" in this respect. However, the Embden-Meyerhof-Parnas (EMP) pathway was dominant in the locus ceruleus, while the WARBURG-DICKENS pathway (hexose monophosphate shunt = HMP shunt) was dominant in the nucleus dorsalis n. vagi in the present study. This descrepancy may strongly suggest that the locus ceruleus is distinctly different from the nucleus dorsalis n. vagi concerning the carbohydrate metabolism, though both nuclei are involved on the same conception "exceptional nuclei". The latter 2 nuclei (the nucleus tractus mesencephalicus n. trigemini and the nucleus n. hypoglossi) considered to be "usual nuclei" in 3 ways as that nerve cells get energy source directly from glucose in the circulating blood, that the 2 nuclei are equipped with enzymes involved in the EMP pathway and the HMP shunt to the same degree, and that they are rich in the tricarboxylic acid (TCA) cycle. The nucleus tractus mesencephalicus n. trigemini revealed considerably variable reactions for the hexokinase, aldolase, glucose-6-phosphate dehydrogenase and lactic dehydrogenase in the present study.