WESTERN blot analysis using several antibodies showed that rat spinal
cord contained abundant immunostainable heme oxygenase-2 (HO-2) and ba
rely detectable levels of heme oxygenase-1 (HO-1). Anti-HO-2 antibody
stained large anterior horn motoneurones and numerous smaller neurons
throughout spinal cord gray matter including the dorsal root entry zon
e. HO-2(+) astrocytes were not evident in gray matter although their p
resence cannot be ruled out. The distribution of HO-2(+) neurons was c
ompared with the distribution of cells containing NADPH-diaphorase (NA
DPH-d) activity, a marker for nitric oxide synthase. NADPH-d activity
was restricted to far fewer neurons, many of which were close to the c
entral canal and dorsal root entry zone.