title: Immunohistochemical localization of nitric oxide synthase and soluble guanylyl cyclase in the ventral cochlear nucleus of the rat.
abstract: The diffusible messenger nitric oxide (NO) is implicated in auditory processing. It acts in the brain largely through activation of soluble guanylyl cyclase (sGC), a heterodimer comprised of alpha and beta subunits. The authors used immunohistochemistry to study the NO/guanosine 3',5'-cyclic monophosphate (cGMP) pathway in the cochlear nucleus of Sprague-Dawley rats. Central fibers of the cochlear nerve were stained for neuronal nitric oxide synthase (NOS-I) but not for sGCbeta. Within the ventral cochlear nucleus, a large fraction of principal cells were immunopositive for both NOS-I and sGCbeta; these cells could be seen at times receiving contacts from NOS-I-positive fibers. sGC staining of somatic cytoplasm extended into the distal dendritic tree. At variance with this pattern, NOS-I was concentrated mainly in somata. Double-labeling experiments showed that most of the principal neurons expressed both antigens. By contrast, in the granule cell domain, small cells that were immunopositive for NOS-I rarely corresponded to those that were immunopositive for sGC. To assess whether NOS-I and sGC immunoreactivities colocalize with their respective catalytic activities, the authors performed multiple labeling with L-citrulline (a by-product of the formation of NO from L-arginine) and cGMP, respectively. L-citrulline was restricted to NOS-I-positive elements, and the large majority of NOS-expressing neurons were positive for citrulline. Multiple labeling revealed that almost all sGC-positive neurons also accumulated cGMP both in the ventral cochlear nucleus and in the granule cell domain. These data suggest that NO is a signaling molecule in the cochlear nucleus, perhaps functioning in both a paracrine manner and an autocrine manner.
authors.affiliation: Department of Cell Biology and Anatomy, University of North Carolina, CB 7090, Chapel Hill, NC 27599, USA. alain.burrette@med.unc.edu
authors.forename: A
authors.initials: A
authors.lastname: Burette
authors.forename: P
authors.initials: P
authors.lastname: Petrusz
authors.forename: H H
authors.initials: HH
authors.lastname: Schmidt
authors.forename: R J
authors.initials: RJ
authors.lastname: Weinberg
mesh_terms: D000818:Animals; D002956:Citrulline / Q000378:metabolism; D017626:Cochlear Nucleus / Q000166:cytology / Q000201:enzymology*; D006152:Cyclic GMP / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology
chemical_list: D002956:Citrulline; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase; D006152:Cyclic GMP