Induction of NADPH diaphorase nitric oxide synthase in the spinal cord motor neurons of rats following a single and multiple non-penetrative blasts

The present study has demonstrated the induction of nicotinamide adenine di nucleotide phosphate-diaphorase (NADPH-d) reactivity and nitric oxide synth ase-like immunoreactivity (NOS-LI) in the ventral horn motoneurons of the s pinal cord in rats subjected to a single or multiple underground, or a sing le surface blast. Both enzyme activities were first detected in some motone urons in laminae VIII and IX of Rexed, 3 hours after the blast. Some NADPH- d and NOS-LI positive neurons were also distributed in Laminae VI and VII. The number and intensity of the labelled cells appeared to increase progres sively, peaking at 2-3 days after the blast but were drastically reduced th ereafter, so that at 7 days after the blast only a few positive neurons wer e observed. In rats killed at 2 weeks and in longer surviving intervals, i. e. up to 1 month, NADPH-d/NOS reactivity in the ventral horn motor neurons had diminished. The functional significance of the transient expression of neuronal NADPH-d/NOS after the blasts remains uncertain, although from a sp eculative point of view, the induction of these enzymes probably would refl ect an increased production of nitric oxide (NO). In view of the lack of at rophic changes in most, if not all, of motor neurons, it is suggested that the increased levels of NO production after the blast injury may be involve d in a neuroprotective function.