SPINAL-CORD GRAY-MATTER LAYERS RICH IN NADPH DIAPHORASE-POSITIVE NEURONS ARE REFRACTORY TO ISCHEMIA-REPERFUSION-INDUCED INJURY - A HISTOCHEMICAL AND SILVER IMPREGNATION STUDY IN RABBIT

Silver impregnation analysis of neuronal damage and concurrent histoch emical characterization of NADPH diaphorase-positive neuronal pools in the rabbit lumbosacral segments was performed during and after transi ent spinal cord ischemia. Strongly enhanced staining of NADPH diaphora se-positive neurons and their processes appeared in the superficial do rsal horn (laminae I-III), the pericentral region (lamina X) of lower lumbar segments, the lateral collateral pathway, and mainly in neurons of the sacral parasympathetic nucleus in the S2 segment at the end of 40 min of abdominal aorta ligation or 1 day after reperfusion. Despit e the development of extensive neuronal degeneration in the central gr ay matter (laminae IV-VII) between 1 and 4 days after ischemia, a numb er of nonnecrotizing neurons localized in the areas corresponding with the distribution of NADPH diaphorase-positive neurons was detected, s uggesting a selective resistance of these classes of neurons against t ransient ischemic insult. While the precise mechanism of the observed resistance is not known, it is postulated that region-specific synthes is of nitric oxide and its vasodilatatory effect during the period of incomplete spinal ischemia may account for the observed selective resi stance of these spinal cord neurons to transient ischemia. (C) 1997 Ac ademic Press.