Immunocytochemical characterization of rat brainstem neurons with vagal afferent input from the stomach challenged by acid or ammonia.
Exposure of the gastric mucosa to backdiffusing acid is signalled to the brainstem via vagal afferents. This study examined whether exposure of the Sprague-Dawley rat stomach to hydrochloric acid (HCl) or ammonium hydroxide (NH4OH), a noxious chemical produced by Helicobacter pylori, activates different vagal afferent pathways as reflected by different circuitries in the medullary brainstem. Two hours after intragastric treatment with HCl or NH4OH the activation of neurons in the nucleus tractus solitarii at the rostrocaudal extension of the area postrema (NTSAP) was visualized by c-Fos immunohistochemistry and their chemical coding characterized by double-labelling immunohistochemistry. Exposure of the rat gastric mucosa to HCl (0.15-0.5 M) or NH4OH (0.1-0.3 M) led to a concentration-dependent expression of c-Fos in the NTSAP. The number and distribution of NTSAP neurons activated by 0.35 M HCl and 0.3 M NH4OH were similar; the highest number of activated neurons occurring in the medial part of the NTSAP. Some 60% of the NTSAP neurons activated by intragastric HCl and NH4OH stained for the high affinity glutamate transporter EAAC1, while some 30% contained calbindin or neuropeptide Y. Glutamate receptors of the N-methyl-D-aspartate type were found on approximately 50% of the c-Fos-positive cells in the NTSAP, whereas tachykinin NK1, NK2 and NK3 receptors were present on 5-10% of the activated neurons. The similar number and distribution of c-Fos-expressing neurons within the NTSAP and their identical chemical coding indicate that exposure of the rat stomach to backdiffusing concentrations of HCl and NH4OH activates the same vagal afferent-NTSAP pathway.
Danzer
Marion
M
Department of Experimental and Clinical Pharmacology, University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
Samberger
Claudia
C
Schicho
Rudolf
R
Lippe
Irmgard Th
IT
Holzer
Peter
P
D027322:Amino Acid Transport System X-AG / Q000187:drug effects / Q000378:metabolism; D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D031608:Area Postrema / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D064026:Calbindins; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D050580:Excitatory Amino Acid Transporter 3; D005260:Female; D005753:Gastric Mucosa / Q000187:drug effects / Q000294:innervation*; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D009478:Neuropeptide Y / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D018039:Receptors, Tachykinin / Q000187:drug effects / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D027981:Symporters / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*; D017833:Visceral Afferents / Q000187:drug effects / Q000502:physiology*
D027322:Amino Acid Transport System X-AG; D064026:Calbindins; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; D009478:Neuropeptide Y; D016760:Proto-Oncogene Proteins c-fos; D016194:Receptors, N-Methyl-D-Aspartate; D018039:Receptors, Tachykinin; D064030:S100 Calcium Binding Protein G; C493398:Slc1a1 protein, rat; D027981:Symporters; D018698:Glutamic Acid; D000641:Ammonia; D006851:Hydrochloric Acid