NADPH-DIAPHORASE, NITRIC OXIDE SYNTHASE, AND TYROSINE HYDROXYLASE
IN THE DIENCEPHALON OF THE RHODEUS SERICEUS (CYPRYNIDAE: TELEOSTEI)
E. V. Pushchina,1 D. K. Obukhov 2
1 Institute of Marine Biology, Far East Branch of RAS, Vladivostok,
and 2 Department of Cytology and Histology, St. Petersburg State University;
e-mail: puschina@mail.ru, dkobukhov@yandex.ru
The presence and distribution of nitric oxide synthase (NOS)-like neurons as well as tyrosine hydroxylase-
immunoreactive (TH) neurons was studied in the diencephalon of the cypriniform teleost Rhodeus sericeus.
The anatomical relationships between tyrosine hydroxylase (TH)- and nitric oxide synthase (NOS)-containing
cells were visualized both by NOS-immunohistochemistry and NADPH-histochemistry. Immunohistochemical
labeling and morphological studies were performed on the same sections. The results reported in this paper
show that both a NOS and TH activity are present in the preoptic region, posterior tuberculum, paraventricular
organ and hypothalamus of R. sericeus. Putative nitrergic neurons were identified in all major hypophysiotrophic
nuclei of the R. sericeus brain using both NADPH-d histochemistry and nNOS immunohistochemistry. In
the preoptic region, nitrergic neurons were found in both the parvocellular and the magnocellular nuclei. Within
these nuclei, the distribution of NADPH-d reactivity was similar to that of nNOS immunoreactivity. However,
we found no evidence of colocalization of NADPH-d and nNOS in consecutive sections. NOS- and TH-containing
neurons were observed in all the nuclei under study (hypothalamus, posterior tuberculum, ventral thalamus)
and telencephalon (preoptic region), although most neurons showing the coexistence of both substances
were mainly located in the preoptic nucleus and hypothalamus, some labelled neurons were found in the posterior
tuberculum. Most of the cerebrospinalliquor-contacting cells (LCNs) in diencephalic periventricular area of
R. sericeus were TH-immunoreactive. Also, a large number of nitrergic small LCNs distributed throughout the
third ventricle were observed in these regions. The data obtained supports the existence of a nitrergic cirmventricular
system in teleost. LCNs in R. sericeus are thought to be involved in osmoregulatory functions as osmosensitive
neurons. Due to their chemical properties, NO produced by these cells might play an important role in the
maintenance and regulation of CSF homeostasis through the modulation of cerebral blood flow.
Key words: tyrosine hydroxylase, neuronal nitric oxide synthase, NADPH-diaphorase, Cyprynidae, diencephalic
hypophysiotrophic nuclei, cerebral blood flow regulation
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