Variation in the localization of NADPH-d positive neurons in the gray matter of the spinal cord in different species

The presence of NADPH-diaphorase (NADPH-d) activity was investigated in the thoracic part of rat, rabbit and pheasant spinal cords. Histochemical method for visualization of NADPH-d was used in this study. The comparison between all spinal cord regions (laminae) in three experimental species revealed marked differences. Especially in the ventral horn, the presence of NADPH-d activity was different. While the pheasant ventral horn possessed number of scattered intensively stained neurons, the rat and rabbit showed no NADPH-d activity in this region. Pericentral area (lamina X), intermediate zone (lamina VII) and dorsal horn revealed the presence of NADPH-d positive neurons in all examinated species although they differed in the distribution of NADPH-d activity. In summary, it can be suggested that the observed differences in the presence and distribution of NADPH-d activity among species may reflect their different phylogenetic development. As a consequence, different NO function in spinal cord of various species can be presumed. (Fig. 10, Ref. 28.)