Nitric oxide synthase/nicotinamide adenine dinucleotide phosphate-diaphorase in the brainstem trigeminal nuclei after transection of the masseteric nerve in rats

In this study, the responses of nicotinamide adenine dinucleotide phosphate -diaphorase (NADPH-d) and neuronal nitric oxide synthase (nNOS) activities were quantitatively analyzed at different times in both ipsilateral and con tralateral sides of trigeminal nuclei, after unilateral trigeminal muscle n erve transection, in Sprague Dawley rats. In the control animals, both NADP H-d- and nNOS-positive neurons were constitutively distributed in the rostr olateral solitary tract nucleus, dorsomedial part of trigeminal nucleus ora lis (Vo/Sn), and superficial layers (Vcl/ll) of the trigeminal nucleus caud alis (Vc). NADPH-d-positive neurons appeared in the trigeminal mesencephali c nucleus ipsilaterally at 5 days (mean SEM: 30.5 +/- 5.6) and were maintai ned until 8 weeks (33 +/- 10.6) after the denervation. In the trigeminal mo tor nucleus, NADPH-d-positive neurons appeared transiently and bilaterally, peaking at 1 week (663.5 +/- 156.2, ipsilateral side; 687.5 +/- 118.6, con tralateral side) after unilateral denervation of the masseteric nerve. In b oth Vo/Sn and Vc, the number of NADPH-d-positive neurons in the control ani mals showed a decrease at 3 days but significantly increased from 5 days to 1 week and gradually fell to the control values by 8 weeks after the dener vation. There were no significant differences observed between the two side s in either Vo/Sn or Vc. nNOS-positive neurons were similarly distributed a nd the numbers of labeled neurons were similar to those of NADPH-d-positive neurons after the denervation, although the changes were delayed by approx imately 1 week. In conclusion, after unilateral nerve transection, the peak NADPH-d activity occurs 1 week prior to nNOS activity. (C) 2001 Wiley-Liss , Inc.