DEVELOPMENTAL-CHANGES IN THE LOCALIZATION OF THE TRANSPLASMA MEMBRANE NADH-DEHYDROGENASES IN THE RAT-BRAIN

The function of transplasma membrane oxidoreductases (PMO's) has been further studied by means of investigating the postnatal (PN) developmental changes in the tissue localization of six isoenzymes previously characterized (see accompanying paper). The changes were followed in the midbrain for PMO-I, -II, and -V and in the brainstem for PMO-III, -IV and -VI. PMO-I is not observed before PN5 and develops as long vertical fibers located mainly in the pontine nucleus and in the dorsal raphe nucleus until it merges all over the midbrain except for the aqueduct and the superior colliculus after PN10. At that stage it is highly expressed in the trigeminal nucleus and the dorsal raphe, but its expression then strongly decreases and PMO-I disapears almost completely later on. Similarly PMO-II only develops around PN5, first in the dorsal and caudal linear raphe and later on (at PN7) also in the pontine nucleus and in the median raphe; at PN PMO-II gradually had vanished from these areas and strongly developed in the dorsal raphe and in the mesencephalic trigeminal nucleus. Later on PMO-II alos decreases from these areas. PMO-III slowly develops within the gigantocellular reticular nucleus from PN1 to PN5 and later on reaches the facial nucleus (after PN5), the density of PMO-III in these regions at PN10 being much higher than in the adult. PMO-IV follows a similar developmental pattern in the midbrain, with an optimal density around PN10 also. PMO-V appears only at about PN5, first within the dorsal raphe in parallel fibers and in multipolar neurons. It disappears from the fibers around PN10 and remains present in neurons up to adulthood. PMO-VI appears at early stages within the gigantocellular reticular nucleus and after PN5 within the central gray in vertical fibers. At later stages PMO-VI is found in the spinal trigeminal nucleus, at first within the neuropil then in multipolar neurons that remain present up to adulthood. These datas suggested that the different isoenzymes are expressed at various stages in specific areas. The role of PMO's in neuronal development is discussed.