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Vagal preganglionic axons arborize in the myenteric plexus into two types: nitrergic and non-nitrergic postganglionic motor pools?

Authors :
Jaffey, D. M.
McAdams, J. L.
Baronowsky, E. A.
Black, D.
Powley, T. L.
Source :
American Journal of Physiology: Regulatory, Integrative & Comparative Physiology; Mar2023, Vol. 324 Issue 3, pR305-R316, 12p
Publication Year :
2023

Abstract

Vagal preganglionic neurons innervate myenteric ganglia. These autonomic efferents are distributed so densely within the ganglia that it has been impractical to track individual vagal axons through the myenteric plexus with tracer labeling. To evaluate whether vagal efferent axons evidence selectivity, particularly for nitrergic or non-nitrergic myenteric neurons within the plexus, we limited the numbers and volumes of brainstem dextran biotin tracer injections per animal. Reduced labeling and the use of immunohistochemistry generated cases in which some individual axons could be distinguished and traced in three dimensions (Neurolucida) within and among successive (up to 46) myenteric ganglia. In the myenteric plexus of all stomach regions, the majority (~86%) of vagal efferents were organized into two distinct subtypes. One subtype (~24% of dextran-labeled efferents, designated "primarily nitrergic") selectively contacted and linked--both within and between ganglia--nitric oxide synthase positive (nNOS+) neurons into presumptive motor modules. A second subtype (~62% of efferents, designated "primarily non-nitrergic") appeared to selectively contact and link--both within and between ganglia--non-nitrergic enteric neurons into a second type of effector ensemble. A third candidate type (~14% of labeled preganglionics), appeared to lack "nitrergic selectivity" and to contact both nNOS+ and nNOS-enteric neurons. In addition to the quantitative assessment of the efferent axons in stomach, qualitative observations of the proximal duodenum indicated similar selective vagal efferent projections, in proportions comparable with those evaluated in the stomach. Limited injections of tracer, three-dimensional (3-D) tracing of individual axons, and histochemistry of myenteric neurons might distinguish additional efferent phenotypes. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
03636119
Volume :
324
Issue :
3
Database :
Complementary Index
Journal :
American Journal of Physiology: Regulatory, Integrative & Comparative Physiology
Publication Type :
Academic Journal
Accession number :
161956071
Full Text :
https://doi.org/10.1152/ajpregu.00260.2022