NADPH-DIAPHORASE HISTOCHEMISTRY REVEALS OLIGODENDROCYTES IN THE RAINBOW-TROUT (TELEOSTS)

We studied the distribution of NADPH-diaphorase (NADPHd) in the brain of the rainbow trout. Not only neurons but also tanycytes and oligoden drocytes showed NADPHd positivity. Interestingly, staining of oligoden drocytes was delicate and revealed fine characteristics of these cells , comparable to those revealed by classical 'oligodendrocyte methods' in mammals (such as the rich branching of processes and their associat ion with myelin sheaths). NADPHd histochemistry indicated that trout o ligodendrocytes are heterogeneous as regards cell size, shape and numb er of processes, and that there is a positive correlation between the size of axons and that of the associated oligodendrocytes. NADPHd hist ochemistry thus appears to be a useful method for the study of oligode ndrocyte populations in bony fishes. Furthermore, this is the first re port of NATADPHd activity in oligodendrocytes of any vertebrate.