Search

Nitric oxide synthase (NOS) has been reported to be involved with both bone healing and bone metabolism. The aim of this study was to test the null hypothesis that there is no correlation between new bone formation during mandibular distraction osteogenesis and NOS expression in the trigeminal ganglion of rats. Newly formed tissue during distraction osteogenesis and trigeminal NOS expression measured by the NADPH-diaphorase (NADPH-d) reaction were evaluated in 72 male Wistar rats by histomorphometric and histochemical methods. In animals submitted to 0.5 mm/day distraction osteogenesis, the percentage of bone tissue was higher in the basal area of the mandibles compared with the center and significantly increased through the experimental periods (P < 0.05). At the sixth postoperative week, the difference in bone formation between the continuous and acute distraction osteogenesis groups was the highest. Significant correlation between new bone formation by distraction osteogenesis and NADPH-d-reactive neurons was found, varying according to neuronal cell size (r = -0.6, P = 0.005, small cells strongly stained; r = 0.5, P = 0.018, large cells moderately stained). The results suggest that NOS may play a role in the bone healing process via neurogenic pathways, and the phenomenon seems to be neuronal cell morphotype-dependent. Further studies are now warranted to investigate the mechanistic link between the expression of trigeminal NOS and mandibular new bone formation by distraction osteogenesis.

Nitric oxide (NO) is a free radical gas with important roles in the host's immune response against viral infections. In this study, we examined the kinetics and distribution of nitric oxide synthase (NOS) expression during the early steps of infection of the porcine nervous system by the alphaherpesvirus pseudorabies virus (PRV). To this end, we examined changes in the expression of the three major NOS isoforms, neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS), by immunohistochemistry in the trigeminal ganglia and brain of pigs inoculated intranasally with a virulent PRV strain. The results obtained show that infection of the porcine nervous system by PRV induced a rapid and progressive increment in NOS expression that coincided in timing, location, and magnitude with those of virus propagation in the nervous tissue. A major finding of this study was that PRV caused not only nNOS and iNOS induction in a variety of cell types, but also eNOS up-regulation in endothelial cells and neurons; therefore, all possible sources of NO are activated and probably contribute to the overproduction of NO during infection with the neurotropic alphaherpesvirus PRV in its natural host.

The expression of neuronal nitric oxide synthase (nNOS) in the trigeminal ganglia (TG) of the infrared-sensitive crotaline snake Trimeresurus flavoviridis was studied immunohistochemically. The percentage of nNOS-positive (+) neurons in the TG was significantly higher (about 3.5-fold, P<0.001) in the mandibular division than in the infrared-sensory processing area (the maxillary division and ophthalmic ganglion). nNOS was found in varying sizes of TG neurons. However, nNOS (+) neurons were more abundant in small and large neurons than in medium-sized neurons, which include most of the infrared-sensitive neurons of the TG. These findings suggest that nNOS may be involved in normal physiological functions, such as the transmission of tactile, vibrotactile, and nociceptive sensations in the TG, rather than in infrared sensory processing in this species.

It is generally considered that parasympathetic postganglionic nerve fibers innervating the lacrimal gland (LG) arise from the pterygopalatine ganglion (PPG), while sympathetic and sensory innervations arise from the superior cervical ganglion (SCG) and trigeminal ganglion (TG), respectively. Recently, we reported for the first time that the parasympathetic innervation of the cat LG was also provided by the otic ganglion (OG) and ciliary ganglion (CG), and that the sensory innervation was also provided by the superior vagal ganglion (SVG) and superior glossopharyngeal ganglion (SGG). To determine if nitric oxide (NO) is a neurotransmitter of the autonomic and sensory neurons innervating the LG, we injected the cholera toxin B subunit (CTB) as a retrograde tracer into the cat LG, and used double-labeling fluorescent immunohistochemistry for CTB and nitric oxide synthase (NOS). We found that NOS-/CTB-immunofluorescent double-labeled perikarya were localized in the PPG, OG, TG, SVG and SGG, but not in the CG and SCG. The highest numbers of NOS-/CTB-immunofluorescent double-labeled neurons were found in the PPG and TG. In addition, we examined the presence of nitrergic nerve fibers in the LG using NADPH-d histochemistry and found that a large amount of NADPH-d-stained nerve fibers were distributed around the glandular acini and in the walls of glandular ducts and blood vessels. This study provides the first direct evidence showing that NO may act as a neurotransmitter or modulator involved in the parasympathetic and sensory regulation of lacrimal secretion and blood circulation, but may not be implicated in the sympathetic control of LG activities, and that nitrergic nerve fibers in the LG arise mainly from parasympathetic postganglionic neurons in the PPG and sensory neurons in the TG. The present results suggest that NO plays an important role in the regulation of LG activities.

Nitric oxide (NO) influences electrophysiological and morphological parameters of the mammalian cochlea. Recently, the isoform of the NO-producing enzyme neuronal NO synthase (nNOS) has been demonstrated in spiral ganglion cells and olivocochlear neurons. The cochlea is also innervated by fibers stemming from the trigeminal ganglion (TG) and superior cervical ganglion (SCG). Whether these ganglion cells contain nNOS is not known yet. We therefore identified TG and SCG cells upon injection of Fluoro-Gold (FG) into the cochlea and retrograde neuronal transport of FG in rat and guinea pig. These ganglion cells were investigated for neuronal NOS immunohistochemically. Perikarya labeled by FG were found in the ipsilateral TG and SCG. In both species investigated, a considerable number of FG-labeled TG cells were also nNOS-immunoreactive whereas SCG cells were not. These data, demonstrating the existence of nNOS-containing TG cells that project to the cochlea, provide evidence that these neurons are further sources of nitric oxide in the cochlea.

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.

The trigeminal ganglion (TrG) and mesencephalic trigeminal nucleus (MTN) neurons are involved in the transmission of orofacial sensory information. The presence of nitric oxide (NO), a putative neurotransmitter substance in the nervous system, was examined in the cat TrG and MTN using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry. In the TrG, where the majority of the trigeminal primary afferent perikarya are located, most of the intensely NADPH-d/ NOS-stained cells were small in size and distributed randomly throughout the ganglion. The medium-sized neurons were moderately stained. A plexus of pericellular varicose arborizations around large unstained ganglion cells and densely stained fibers in-between could also be observed. In the caudal part of the MTN, both NADPH-d activity and NOS immunoreactivity was present in MTN neurons. In addition, a few scattered NADPH-d/NOS-containing neurons were found in the mesencephalic-pontine junction part of the nucleus. In contrast, only nerve fibers and their terminals were present at a more rostral level in the mid- and rostral MTN. MTN neuronal perikarya were enveloped in fine basket-like NADPH-d/ NOS-positive networks. Differential expression patterns of NOS and its marker NADPH-d suggest that trigeminal sensory information processing in the cat MTN is controlled by nitrergic input through different mechanisms. We introduce the concept that NO can act as a neurotransmitter in mediating nociceptive and proprioceptive information from periodontal mechanoreceptors but may also participate in modulating the activity of jaw-closing muscle afferent MTN neurons.

NADPH-diaphorase histochemical technique was applied to demonstrate the catalytic activity of nitric oxide synthase (NOS) in the nerve fibers supplying some porcine cerebral blood vessels, as well as in ganglia thought to be their possible sites of origin. Five sexually mature Large With Polish race sows were used. The following blood vessels and their branches were studied: the basal cerebral artery, medial cerebral artery, arteries of the circle of Wills as well as arteries located in the arachnoidea. The activity of NADPH-d was visualised in whole-mount preparations from the above listed blood vessels. The presence of NADPH-d was additionally studied in the ganglia of trigeminal nerves, the sensory ganglia of vagus nerves, the pterygopalatine and cranial cervical ganglia. NADPH-d activity was found in nerve fibres supplying all the studied arteries. Larger blood vessels, the basal cerebral artery, medial cerebral artery and arteries of the circle of Wills possessed very dense NADPH-d-positive nerve plexuses while arachnoidal arteries were poorly innervated by only single nerves. The vascular nerve fibers formed bundles varying in thickness, from very thick bundles often interchanging nerve fibers to quite thin fascicles. Thick bundles were absent from the walls of medium sized vessels and small meningeal arteries where only smaller fascicles or single fibres occurred. NADPH-d-positive neurons and nerve fibres were found in all the ganglia investigated. However, pronounced differences in the number of the positive nerve structures were observed between the ganglia. In the pterygopalatine, trigeminal and sensory ganglia of the vagal nerve the vast majority of neurons were NADPH-d-positive. Numerous NADPH-d-positive nerve fibers occurred within the pterygopalatine and trigeminal ganglion while sensory ganglia of the vagal nerve comprised smaller number of fibres. Small numbers of the neurons and moderate numbers of the nerve fibres occurred in the cranial cervical ganglion. The intensity of NADPH-d reaction in the endothelium was constant independent of the size of the vessels studied.