Anatomical survey of paravertebral sympathetic chain in adult mice Open Access

Choi, Mi Hyun (Fall 2017)

Permanent URL: https://etd.library.emory.edu/concern/etds/pk02c973d?locale=en
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Abstract

The predominant purpose of thoracic paravertebral sympathetic ganglia (tPSG) is innervation of vasculature for control of vasomotor function. Despite this important function, anatomical and physiological properties of sympathetic postganglionic neuron (SPN) populations in the tPSG are not well-understood. Consequently, their role in vascular changes observed after injury or disease is barely known. Here, the numbers and diameters of two major SPN chemical phenotypes – cholinergic and noradrenergic – were determined along the rostrocaudal tPSG axis comprising segments T1-T13. I used immunohistochemistry to amplify GFP detection in choline acetyltransferase (ChAT) GFP-expressing cholinergic neurons and to detect tyrosine hydroxylase (TH) noradrenergic neurons. Mice averaged 13,107.5 neurons (n=2) but inter-animal variability in number was enormous (6,494 vs.19,721). Of these, 97.2% were noradrenergic and 2.8% were cholinergic. Examination of additional counts from 6 mice in select ganglia (T3, T5 and T9) supported a remarkable inter-animal variability in numbers counted that were not overtly sex related. The number of noradrenergic SPNs peaked at T7 and T8. The number of cholinergic SPNs was greater in rostral (T1-T6) compared to caudal segments (T7-T13; p<0.001), presumably due to preferential innervation for forepaw footpad sweat glands. Noradrenergic SPN diameter (17.5µm) was slightly but significantly larger than the average cholinergic SPN diameter (16.7µm; p<0.0001). Both noradrenergic mean cell diameter and cholinergic mean cell diameter differed significantly between segments (p<0.0001 for each). Overall, this study compared the numbers, diameters and segmental distribution of noradrenergic and cholinergic neurons in the sympathetic paravertebral thoracic chain of mice. Most notable observations were the expected dominance of adrenergic neurons and the remarkable variability on neurons numbers between animals.

Table of Contents

Introduction - 1

Methods - 15

Results - 18

Discussion - 29

References - 36

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