Histochemical observation of nitric oxide synthase in trigeminal ganglion of rats with experimental pulpitis

In order to understand the roles of nitric oxide (NO) in pulpalgia and pulpitis, the histochemistry of nitric oxide synthase (NOS) in the neurons of trigeminal ganglion in experimental pulpitis rat and human inflammatory dental pulp tissues were histochemically studied by NADPH-diaphorase (NADPH-D) techniques. Results showed that NADPH-D positive neurons were scattered in rat trigeminal ganglions, but the sizes of positive neurons were not changed. None of NOS-positive fibers was found in human normal and inflammatory dental pulp tissues. The results suggested that NOS in trigeminal ganglion might play an important role in sensory transmission and regulation of pulpalgia. The absence of NOS-positive nerves in human pulp suggested that NO may not be related to inflammatory stimulation and transmission in dental pulp tissues.