Document Detail

A genetic approach for investigating vagal sensory roles in regulation of gastrointestinal function and food intake.
MedLine Citation:
PMID:  16677865     Owner:  NLM     Status:  MEDLINE    
Sensory innervation of the gastrointestinal (GI) tract by the vagus nerve plays important roles in regulation of GI function and feeding behavior. This innervation is composed of a large number of sensory pathways, each arising from a different population of sensory receptors. Progress in understanding the functions of these pathways has been impeded by their close association with vagal efferent, sympathetic, and enteric systems, which makes it difficult to selectively label or manipulate them. We suggest that a genetic approach may overcome these barriers. To illustrate the potential value of this strategy, as well as to gain insights into its application, investigations of CNS pathways and peripheral tissues involved in energy balance that benefited from the use of gene manipulations are reviewed. Next, our studies examining the feasibility of using mutations of developmental genes for manipulating individual vagal afferent pathways are reviewed. These experiments characterized mechanoreceptor morphology, density and distribution, and feeding patterns in four viable mutant mouse strains. In each strain a single population of vagal mechanoreceptors innervating the muscle wall of the GI tract was altered, and was associated with selective effects on feeding patterns, thus supporting the feasibility of this strategy. However, two limitations of this approach must be addressed for it to achieve its full potential. First, mutation effects in tissues outside the GI tract can contribute to changes in GI function or feeding. Additionally, knockouts of developmental genes are often lethal, preventing analysis of mature innervation and ingestive behavior. To address these issues, we propose to develop conditional gene knockouts restricted to specific GI tract tissues. Two genes of interest are brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), which are essential for vagal afferent development. Creating conditional knockouts of these genes requires knowledge of their GI tract expression during development, which little is known about. Preliminary investigation revealed that during development BDNF and NT-3 are each expressed in several GI tract regions, and that their expression patterns overlap in some tissues, but are distinct in others. Importantly, GI tissues that express BDNF or NT-3 are innervated by vagal afferents, and expression of these neurotrophins occurs during the periods of axon invasion and receptor formation, consistent with roles for BDNF or NT-3 in these processes and in receptor survival. These results provide a basis for targeting BDNF or NT-3 knockouts to specific GI tract tissues, and potentially altering vagal afferent innervation only in that tissue (e.g., smooth muscle vs. mucosa). Conditional BDNF or NT-3 knockouts that are successful in selectively altering a vagal GI afferent pathway will be valuable for developing an understanding of that pathway's roles in GI function and food intake.
Edward Alan Fox
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Review     Date:  2006-05-04
Journal Detail:
Title:  Autonomic neuroscience : basic & clinical     Volume:  126-127     ISSN:  1566-0702     ISO Abbreviation:  Auton Neurosci     Publication Date:  2006 Jun 
Date Detail:
Created Date:  2006-06-08     Completed Date:  2006-09-25     Revised Date:  2009-08-12    
Medline Journal Info:
Nlm Unique ID:  100909359     Medline TA:  Auton Neurosci     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  9-29     Citation Subset:  IM    
Purdue University, Department of Psychological Sciences, 703 Third Street, West Lafayette, Indiana 47907, USA.
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MeSH Terms
Afferent Pathways / cytology,  physiology*
Animals, Newborn
Brain-Derived Neurotrophic Factor / genetics,  metabolism
Digestive System / metabolism
Digestive System Physiological Phenomena*
Eating / genetics*
Embryo, Mammalian
Gene Expression Regulation, Developmental / genetics
Genetic Techniques*
Mice, Transgenic
Neurons, Afferent / physiology
Neurotrophin 3 / genetics,  metabolism
Vagus Nerve / cytology,  physiology*
Grant Support
Reg. No./Substance:
0/Brain-Derived Neurotrophic Factor; 0/Neurotrophin 3

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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