Subcellular localization of nitric oxide synthase in the cerebral ventricular system, subfornical organ, area postrema, and blood vessels of the rat brain

Abstract

The distribution of neuronal nitric oxide synthase (nNOS) has been studied in the more rostral portion of the lateral ventricle, subfornical organ, area postrema and blood vessels of the rat central nervous system. nNOS was located by means of a specific polyclonal antibody, by using light and electron microscopy. Light microscopy showed immunoreactive varicose nerve fibers and terminal boutons-like structures in the lateral ventricle, positioned in supra- and subependimal areas. The spatial relationships between immunoreactive neuronal processes and the wall of the intracerebral blood vessels were studied. Electron microscopy showed numerous nerve fibers in the wall of the lateral ventricle; many were nNos-immunoreactive and established very close contact with ependymal cells. Immunoreactive neurons and processes were found in the subependymal plate of the ventricular wall, the subfornical organ, the area postrema, and the circularis nucleus of the hypothalamus. In these last three areas, the immunoreactive neurons were found close to the perivascular space of fenestrated and nonfenestrated blood vessels. The nNOS immunoreactivity was localized to the endoplasmic reticulum, cisterns, ribosomes, neurotubules, and in the inner part of the external membrane. In the terminal boutons, the reaction product was found surrounding the vesicle membranes. This distribution showed nNOS as a predominantly membrane-bound protein. The nitrergic nerve fibers present in the wall of the ventricular system might regulate metabolic functions as well as neurotransmission in the subfornical organ, area postrema and circularis nucleus of the hypothalamus.

Ultrastructural localization of NADPH diaphorase and nitric oxide synthase in the neuropils of the snail CNS

“…On the other hand, due to the intensive DAB reaction distributed in the entire axoplasm, the association of NOS to vesicle membranes in presynaptic profiles was not excluded either by the authors describing the cytoplasmic location of NOS (Aoki et al, 1993;Atkinson et al, 2003). Others have emphasized that in preparations of high quality the cytoplasmic NOS-IR material was clearly located around synaptic vesicles (Rodrigo et al, 1997;Sancesario et al, 2000). In accordance with the aforementioned literature data our findings with those from the literature would suggest the association of NOS with the vesicle membranes,.In addition, according to their location and the ultrastructural appearance of the labeled vesicles, the NADPH-d reactive and NOS-IR vesicles seem to represent identical types.…”

“…From this point of view it is rather strange why only a single study has dealt until now with fine details of the localization of NOS (Johansson et al, 1996), in contrast to vertebrates (Rodrigo et al, 1997;Aoki et al, 1998;Rothe et al, 1998;Sancesario et al, 2000;Seress et al, 2005). At light microscopic level NOS was found mainly in sensory-and interneurons, and less in motor neurons of invertebrates, and it seemed that NO mainly acts in an anterograde way (Park et al, 1998;Wildemann and Bicker, 1999;Serfőző et al, 2008).…”

Distribution of NADPH-Diaphorase-Positive Neurons in the Mouse Brain: Differences from Previous Findings in the Rat Brain and Comparison with the Distribution of Serotonergic Neurons.

“…Using immunohistochemical methods to detect the localization of nitric oxide, however, Rodrigo et al [48] demonstrated the presence of positively stained cell bodies and fibers in several areas in the rat brain; i.e. the globus pallidus, the red nucleus, the principal sensory trigeminal nucleus and the locus coeruleus.…”

“…Although a great deal of attention has been paid to the distribution of the 5-HT neurons in the circumventricular organs [58], and recently also to that of NOS [48], there have been few studies concerning the relationship between NOS and 5-HT neurons in the circumventricular organs. The possibility that the nitergic fibers regulate metabolic function in the wall of the ventricular system, and that 5-HT-positive fibers do the same in the subfornical organ, has been discussed [48]. The functions of the circumventricular organs have not yet been elucidated.…”

“…The functions of the circumventricular organs have not yet been elucidated. Indeed, in the ventricular system, NO might mediate regulation of the composition of the cerebrospinal fluid and blood pressure and also modulate the release of hormone and neuropeptides known to participate in the general regulation of fluid balance and blood pressure in the subfornical organ [32,48]. One of the cooperative functions of 5-HT and NO may occur in the pedunculopontine tegmental nucleus.…”