DEVELOPMENTAL-CHANGES IN THE LOCALIZATION OF THE TRANSPLASMA MEMBRANENADH-DEHYDROGENASES IN THE RAT-BRAIN

The function of transplasma membrane oxidoreductases (PMO's) has been further studied by means of investigating the postnatal (PN) developme ntal changes in the tissue localization of six isoenzymes previously c haracterized (see accompanying paper). The changes were followed in th e midbrain for PMO-I, -II, and -V and in the brainstem for PMO-III, -I V and -VI. PMO-I is not observed before PN5 and develops as long verti cal fibers located mainly in the pontine nucleus and in the dorsal rap he nucleus until it merges all over the midbrain except for the aquedu ct and the superior colliculus after PN10. At that stage it is highly expressed in the trigeminal nucleus and the dorsal raphe, but its expr ession then strongly decreases and PMO-I disapears almost completely l ater on. Similarly PMO-II only develops around PN5, first in the dorsa l and caudal linear raphe and later on (at PN7) also in the pontine nu cleus and in the median raphe; at PN PMO-II gradually had vanished fro m these areas and strongly developed in the dorsal raphe and in the me sencephalic trigeminal nucleus. Later on PMO-II alos decreases from th ese areas. PMO-III slowly develops within the gigantocellular reticula r nucleus from PN1 to PN5 and later on reaches the facial nucleus (aft er PN5), the density of PMO-III in these regions at PN10 being much hi gher than in the adult. PMO-IV follows a similar developmental pattern in the midbrain, with an optimal density around PN10 also. PMO-V appe ars only at about PN5, first within the dorsal raphe in parallel fiber s and in multipolar neurons. It disappears from the fibers around PN10 and remains present in neurons up to adulthood. PMO-VI appears at ear ly stages within the gigantocellular reticular nucleus and after PN5 w ithin the central gray in vertical fibers. At later stages PMO-VI is f ound in the spinal trigeminal nucleus, at first within the neuropil th en in multipolar neurons that remain present up to adulthood. These da tas suggested that the different isoenzymes are expressed at various s tages in specific areas. The role of PMO's in neuronal development is discussed.