Localization of NADPHd-exhibiting neurons in the spinal cord of the rabbit

Segmental and laminar distributions of nicotinamide adenine dinucleotide ph osphate diaphorase (NADPHd)-exhibiting neurons were examined in the rabbit spinal cord by using horizontal, sagittal, and transverse sections. A large number of NADPHd-positive neurons in the spinal cord of rabbit appeared to fall into six categories (N1-N6), but others could not be classified. Majo r cell groups of NADPHd-exhibiting neurons were identified in the superfici al dorsal horn and around the central canal at all spinal levels and in the intermediolateral cell column at thoracic and upper lumbar levels. NADPHd- exhibiting neurons of the pericentral region were divided into a thin subep endymal cell column containing longitudinally arranged, small bipolar neuro ns with processes penetrating deeply into the intermediolateral cell column and/or running rostrocaudally in the subependymal layer. The second perice ntral cell column located more laterally in lamina X contains large, intens ely stained NADPHd-exhibiting neurons with long dendrites radiating in the transverse plane. In the pericentral region (lamina X), close association o f NADPHd-exhibiting somata and fibers and mostly longitudinally oriented bl ood vessels were detected. Neurons of the sacral parasympathetic nucleus, s een in segments S1-S3, exhibited prominent NADPHd cellular staining accompa nied by heavily stained fibers extending from Lissauer's tract through lami na I along the lateral edge of the dorsal horn to lamina V. A massive dol s al gray commissure, highly positive in NADPHd staining, was found in segmen ts S1-S3. Scattered positive cells were also found in the deeper dorsal hor n, ventral horn, and white matter. Fiberlike NADPHd staining was found in t he superficial dorsal horn and pericentral region in all the segments studi ed. Dense, punctate, nonsomatic NADPHd staining was detected in the superfi cial dorsal horn, in the pericentral region all along the rostrocaudal axis , and in the nucleus phrenicus (segments C4-C5), nucleus dorsalis (segments Th2-L2), Onuf's nucleus (segments S1-S3), and the dorsal part of the dorsa l gray commissure (S1-S3). J. Comp. Neurol. 406:263-284, 1999. (C) 1999 Wil ey-Liss, Inc.