Capsaicin-resistant vagal afferent fibers in the rat gastrointestinal tract: anatomical identification and functional integrity.
The presence and distribution of vagal fibers and terminals throughout esophagus and gastrointestinal tract that could be anterogradely labeled by nodose ganglion tracer injections was quantitatively assessed in capsaicin- and vehicle-pretreated adult rats, in order to identify the capsaicin-resistant population. Up to 90% of the intraganglionic laminar endings (IGLEs), in the myenteric plexus of the esophagus, and 70-90% in the stomach, as well as 57% of the intramuscular endings or arrays (IMAs) in the fundic stomach survived the capsaicin treatment, while in the upper small intestine only few and in the lower small intestine, the cecum and colon, virtually no IGLEs survived capsaicin treatment. Intramucosal terminals were not assessed. Furthermore, gastric balloon distension-induced c-Fos expression in the dorsal vagal complex was not significantly decreased in capsaicin-treated rats. It is concluded that among primary vagal afferents there is a capsaicin-resistant population that primarily innervates the esophagus and upper gastrointestinal tract, and a capsaicin-sensitive population that innervates mainly the lower tract. At least vagal gastric tension-sensitive afferents also seems to be functionally intact in that they may be capable of synaptically activating second-order neurons in the brainstem.
Berthoud
H R
HR
Pennington Biomedical Research Center, Louisiana State University, Baton Rouge 70808, USA. berthohr@mhs.pbrc.edu
Patterson
L M
LM
Willing
A E
AE
Mueller
K
K
Neuhuber
W L
WL
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002232:Carbocyanines; D002404:Catheterization; D004947:Esophagus / Q000294:innervation*; D005456:Fluorescent Dyes; D008297:Male; D009412:Nerve Fibers / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D009475:Neurons, Afferent / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D009620:Nodose Ganglion / Q000166:cytology; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D013270:Stomach / Q000294:innervation*; D009435:Synaptic Transmission / Q000502:physiology; D014630:Vagus Nerve / Q000033:anatomy & histology / Q000166:cytology*
C101089:CM-DiI; D002232:Carbocyanines; D005456:Fluorescent Dyes; D016760:Proto-Oncogene Proteins c-fos; D002211:Capsaicin