title: Intracallosal neuronal nitric oxide synthase neurons colocalize with neurokinin 1 substance P receptor in the rat.
abstract: The corpus callosum (cc) contains nitric oxide (NO)-producing neurons. Because NO is a potent vasodilator, these neurons could translate neuronal signals into vascular responses that can be detected by functional brain imaging. Substance P (SP), one of the most widely expressed peptides in the CNS, also produces vasomotor responses by inducing calcium release from intracellular stores through its preferred neurokinin 1 (NK1) receptor, thus inducing NO production via activation of neuronal NO synthase (nNOS). Single- and double-labeling experiments were performed to establish whether NK1-immunopositive neurons (NK1IP -n) are found in the rat cc and the extent of NK1 colocalization with nNOS. NK1IP -n were seen to constitute a large neuronal population in the cc and had a distribution similar to that of nNOSIP neurons (nNOSIP -n). NK1IP -n were numerous in the lateral cc and gradually decreased in the more medial portions, where they were few or absent. Intracallosal NK1IP -n and their dendritic trees were intensely labeled, allowing classification into four morphological types: bipolar, round, polygonal, and pyramidal. Confocal microscopic examination demonstrated that nearly all NK1IP -n contained nNOS (96.43%) and that 84.59% of nNOSIP -n co-expressed NK1. These data suggest that the majority of intracallosal neurons can release NO as a result of the action of SP. A small proportion of nNOSIP -n does not contain NK1 and is not activated by SP; these neurons may release NO via alternative mechanisms. The possible mechanisms by which intracallosal neurons release NO are also reviewed.
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020, Ancona, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Barbaresi
authors.forename: Emanuela
authors.initials: E
authors.lastname: Mensà
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lariccia
authors.forename: Genni
authors.initials: G
authors.lastname: Desiato
authors.forename: Mara
authors.initials: M
authors.lastname: Fabri
authors.forename: Santo
authors.initials: S
authors.lastname: Gratteri
mesh_terms: D000818:Animals; D002452:Cell Count; D003337:Corpus Callosum / Q000166:cytology* / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008297:Male; D018613:Microscopy, Confocal; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D010784:Photomicrography; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism*
chemical_list: D018040:Receptors, Neurokinin-1; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat
keywords: NK1; colocalization; corpus callosum; immunocytochemistry; immunofluorescence; nitric oxide