The Journal of Neuroscience, April 1, 1999, 19(7):2755-2764
Immediate-Early Gene Expression in the Inferior Mesenteric
Ganglion and Colonic Myenteric Plexus of the Guinea Pig
Keith A.
Sharkey,
Edward J.
Parr, and
Catherine M.
Keenan
Neuroscience Research Group, Department of Physiology and
Biophysics, University of Calgary, Calgary, Alberta, Canada, T2N
4N1
Activation of neurons in the inferior mesenteric ganglion (IMG) was
assessed using c-fos, JunB, and c-Jun expression in the guinea pig IMG
and colonic myenteric plexus during mechanosensory stimulation and
acute colitis in normal and capsaicin-treated animals. Intracolonic
saline or 2% acetic acid was administered, and mechanosensory
stimulation was performed by passage of a small (0.5 cm) balloon either
4 or 24 hr later. Lower doses of capsaicin or vehicle were used to
activate primary afferent fibers during balloon passage. c-Jun did not
respond to any of the stimuli in the study. c-fos and JunB were absent
from the IMG and myenteric plexus of untreated and saline-treated
animals. Acetic acid induced acute colitis by 4 hr, which persisted for
24 hr, but c-fos was found only in enteric glia in the myenteric plexus
and was absent from the IMG. Balloon passage induced c-fos and JunB in
only a small subset of IMG neurons and no myenteric neurons. However, balloon passage induced c-fos and JunB in IMG neurons (notably those
containing somatostatin) and the myenteric plexus of acetic acid-treated animals. After capsaicin treatment, c-fos and JunB induction by balloon passage was inhibited in the IMG, but there was
enhanced c-fos expression in the myenteric plexus. c-fos and JunB
induction by balloon stimulation was also mimicked by acute activation
of capsaicin-sensitive nerves. These data suggest that colitis enhances
reflex activity of the IMG by a mechanism that involves activation of
both primary afferent fibers and the myenteric plexus.
Key words:
neuropeptide Y; somatostatin; prevertebral ganglia; capsaicin; immediate-early genes; enteric glia
Copyright © 1999 Society for Neuroscience 0270-6474/99/1972755-10$05.00/0