title: Expression of nitric oxide synthase in the preoptic-hypothalamo-hypophyseal system of the teleost Oreochromis niloticus.
abstract: In the present study, we have analyzed the expression of nitric oxide synthase (NOS) in the preoptic-hypothalamo-hypophyseal system of the teleost Oreochromis niloticus. The assay for enzyme activity demonstrated that a constitutive NOS activity is present both in soluble and particulate fractions of the homogenates of diencephalons. Western blot analysis using an antibody against the N-terminus of human nNOS revealed two bands both in the supernatant and in the pellet. One band co-migrates at approximately 150 kDa with that detected in the rat cerebellum homogenates and presumably corresponds to neuronal NOS (nNOS) of mammals. The additional band, which migrates at approximately 180 kDa, might be attributed to an alternatively spliced nNOS isoform. Using NADPH diaphorase (NADPHd) histochemistry in combination with NOS immunohistochemistry, nNOS expression has been detected in preoptic nuclei, hypophysiotrophic nuclei of the ventral hypothalamus, and the pituitary gland. Various degrees of dissociation of NADPHd activity and nNOS immunoreactivity have been detected that could be attributed to the expression of different subtypes of nNOS in the preoptic/hypothalamo/hypophysial system of tilapia. In this paper, we also investigated the colocalization of nNOS with arginine-vasotocin (AVT) by means of immunolabeling of consecutive sections. Results suggest that NO may be colocalized with AVT in a subpopulation of neurosecretory neurons. Present findings suggest that nitric oxide (NO) is implicated in the modulation of hormone release in teleosts in a similar way to mammals.
authors.affiliation: Department of Animal and Human Biology, La Sapienza University, Rome, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Bordieri
authors.forename: Tiziana
authors.initials: T
authors.lastname: Persichini
authors.forename: Giorgio
authors.initials: G
authors.lastname: Venturini
authors.forename: Carla
authors.initials: C
authors.lastname: Cioni
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002531:Cerebellum / Q000378:metabolism; D004555:Electric Fish; D005404:Fixatives / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000166:cytology / Q000201:enzymology*; D007150:Immunohistochemistry / Q000379:methods; D007700:Kinetics; D009252:NADPH Dehydrogenase / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D010913:Pituitary-Adrenal System / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D011301:Preoptic Area / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014668:Vasotocin / Q000378:metabolism
chemical_list: D005404:Fixatives; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D009252:NADPH Dehydrogenase; D014668:Vasotocin