Intestinal mechanosensory neurons ensure relatively constant movement of content from one end of the gut to the other. There are at least three populations of mechanosensory neurons: mechanosensory intrinsic primary afferent neurons that form the afferent limb of intrinsic reflexes; mechanosensory intestinofugal neurons (IFNs) that project their axons outside the intestinal wall to prevertebral ganglia where they make synaptic contact with sympathetic neurons; and mechanosensory colon spinal afferent neurons (SANs) with axon collaterals to prevertebral ganglion neurons. The work proposed in this grant focuses on the latter two populations. The basis for mechanosensitivity in IFNs and colon SANs is not understood. We focus the first part of our work on determining whether the degenerin/epithelial Na+-channel (DEG/ENaC) is a component part of the mechanotransducer in these nerves. We will determine by RT-PCR, immunohistochemistry and confocal 3D imaging if DEG/ENaC subunits are expressed in these nerves and by intracellular and patch clamp recording the role of DEG/ENaC in IFN function. In the second part of our work, we will test our hypothesis that mechanosensory colon SANs with axon collaterals are acid sensitive. DRASIC and the vanilloid receptor (VR1) can be directly activated by protons. We will determine by RT-PCR if DRASIC is present in colon SANs with axon collaterals and by immunohistochemistry whether DRASIC and VR1 are colocalized in these nerves. Next, we will examine the effect of acidic solutions placed in the colon on synaptic input to the release of substance P in prevertebral ganglia, and determine the role DRASIC and VR1 play in acid-evoked responses. The significance of our work is two fold. Firstly, it wil provide data to support the notion that DEG/ENaC cation ion channel bridges the gap between colonic motility and mechanosensitivity in intestinal afferent nerves. Secondly, it will provide data to support the hypothesis that DRASIC and VR1 mediate acid sensitivity in mechanosensitive colon SANs with axon collaterals and that these mechanosensory nerves may be sensitized during inflammation. The basic knowledge derived from our studies is expected to improve the understanding of the functional significance of the molecular components of mechanosensitivity and chemosensitivity of intestinal afferent nerves.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK017632-31
Application #
6912563
Study Section
General Medicine A Subcommittee 2 (GMA)
Program Officer
Hamilton, Frank A
Project Start
1977-07-01
Project End
2007-06-30
Budget Start
2005-07-01
Budget End
2007-06-30
Support Year
31
Fiscal Year
2005
Total Cost
$257,186
Indirect Cost
Name
Mayo Clinic, Rochester
Department
Type
DUNS #
006471700
City
Rochester
State
MN
Country
United States
Zip Code
55905
Matsuda, Nilce Mitiko; Miller, Steven M; Szurszewski, Joseph H (2010) Heme-oxygenase-2 immunolabelling in pig jejunum. Acta Histochem 112:402-6
Vernino, Steven; Ermilov, Leonid G; Sha, Lei et al. (2004) Passive transfer of autoimmune autonomic neuropathy to mice. J Neurosci 24:7037-42
Sha, Lei; Miller, Steven M; Szurszewski, Joseph H (2004) Morphology and electrophysiology of neurons in dog paraventricular nucleus: in vitro study. Brain Res 1010:95-107
Ermilov, Leonid G; Schmalz, Philip F; Miller, Steven M et al. (2004) PACAP modulation of the colon-inferior mesenteric ganglion reflex in the guinea pig. J Physiol 560:231-47
Miller, Steven M; Szurszewski, J H (2003) Circumferential, not longitudinal, colonic stretch increases synaptic input to mouse prevertebral ganglion neurons. Am J Physiol Gastrointest Liver Physiol 285:G1129-38
Ermilov, L G; Miller, S M; Schmalz, P F et al. (2003) Morphological characteristics and immunohistochemical detection of nicotinic acetylcholine receptors on intestinofugal afferent neurones in guinea-pig colon. Neurogastroenterol Motil 15:289-98
Miller, S M; Szurszewski, J H (2002) Relationship between colonic motility and cholinergic mechanosensory afferent synaptic input to mouse superior mesenteric ganglion. Neurogastroenterol Motil 14:339-48
Sha, L; Westerlund, J; Szurszewski, J H et al. (2001) Amplitude modulation of pulsatile insulin secretion by intrapancreatic ganglion neurons. Diabetes 50:51-5
Ermilov, L G; Miller, S M; Schmalz, P F et al. (2000) The three-dimensional structure of neurons in the guinea pig inferior mesenteric and pelvic hypogastric ganglia. Auton Neurosci 83:116-26
Miller, S M (2000) Control of peripheral sympathetic prevertebral ganglion neurones by colonic mechanosensory afferents. Gut 47 Suppl 4:iv28-9; discussion iv36

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