title: Stimulation of cardiac sympathetic afferents activates glutamatergic neurons in the parabrachial nucleus: relation to neurons containing nNOS.
abstract: Our previous studies have demonstrated that stimulation of cardiac sympathetic afferents activates neurons in the parabrachial nucleus (PBN), a region known to play a role in central integration of cardiovascular autonomic reflexes. However, phenotypes of these activated neurons have not been well identified. Glutamate, an important excitatory neurotransmitter in the brain, is involved in PBN-mediated cardiovascular responses. Recent identification of vesicular glutamate transporter 3 (VGLUT3) has provided a novel and unique marker to locate distinctive perikarya of neurons that use glutamate as a neurotransmitter. The action of glutamate in the brain is influenced by nitric oxide. Thus, using triple immunofluorescent labeling, the present study examined expression of c-Fos, an immediate early gene, in the neurons containing VGLUT3 and neuronal nitric oxide synthase (nNOS) in the PBN following stimulation of cardiac sympathetic afferents. In anesthetized cats with bilateral barodenervation and cervical vagotomy, topical application of bradykinin (BK, 1-10 microg/ml, 50 microl, n = 6) on the left ventricle was performed six times, every 20 min. Repeated administration of BK elicited consistent increases in blood pressure over a 100 min period while no changes were noted in the animals treated with the vehicle for BK (0.9% saline, n=5). Compared to control cats, c-Fos expression was increased significantly in the cell bodies containing VGLUT3 as well as both VGLUT3 and nNOS in the external lateral PBN (elPBN) in BK-treated animals (all P < 0.01). In addition, using similar triple-staining method, we noted that fibers of activated neurons containing nNOS in the elPBN co-localized with vesicular glutamate transporter 2 following BK stimulation. These data suggest that glutamatergic neurons represent a cell type in the PBN that is activated by stimulation of cardiac sympathetic afferents. Nitric oxide has the potential to influence the action of glutamatergic neurons in regulation of excitatory cardiovascular responses induced by activation of cardiac sympathetic afferents.
authors.affiliation: Department of Medicine, C240 Medical Science 1, University of California, Irvine, Irvine, CA 92697-4075, USA. zguo@uci.edu
authors.forename: Zhi-Ling
authors.initials: ZL
authors.lastname: Guo
authors.forename: Ali R
authors.initials: AR
authors.lastname: Moazzami
authors.forename: John C
authors.initials: JC
authors.lastname: Longhurst
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D026922:Amino Acid Transport Systems, Acidic / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001920:Bradykinin / Q000008:administration & dosage; D001931:Brain Mapping; D002415:Cats; D002452:Cell Count / Q000379:methods; D004334:Drug Administration Schedule; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D018698:Glutamic Acid / Q000378:metabolism*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D011149:Pons / Q000166:cytology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D014628:Vagotomy / Q000379:methods
chemical_list: D026922:Amino Acid Transport Systems, Acidic; D009419:Nerve Tissue Proteins; D016760:Proto-Oncogene Proteins c-fos; D018698:Glutamic Acid; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D001920:Bradykinin