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The development of neuropeptidergic phenotypes in autonomic neurons in vivo: Evidence that distinct mechanisms may regulate neuropeptide expression

by Tyrrell, Sophia

Abstract (Summary)
The mechanisms by which peptidergic phenotypes of autonomic neurons are determined and regulated are incompletely understood. I have examined the development of four neuropeptides in two sympathetic ganglia, the superior cervical ganglion (SCG) and the stellate ganglion. Using immunocytochemistry, radioimmunoassays and in situ hybridization histochemistry, I have shown that neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), enkephalin (Enk) and calcitonin gene related peptide (CGRP) have distinct developmental patterns of expression. Two peptides were expressed in embryonic ganglia; NPY-IR appeared in almost every embryonic sympathetic cell while VIP-IR was present in a subset of stellate cells. The proportion cells possessing immunoreactivity for these peptides decreased during development. In contrast, Enk- and CGRP-IR first appeared postnatally in a small number of neurons. Enk-IR was predominately found in caudal SCG neurons and CGRP-IR was present in stellate neurons. The proportion of neurons expressing Enk and CGRP increased until after P21 when the number of Enk-IR neurons decreased and the proportion of neurons with CGRP-IR no longer changed. Following treatment of neonatal rats with a single dose of 6-hydroxydopamine (6-OHDA), contact between sympathetic neurons and their targets was transiently interrupted and expression of each neuropeptide was affected in a distinct manner: the proportion of neurons with NPY-IR did not change, VIP-IR was increased in the SCG, but not in the stellate ganglion and the proportion of neurons with either Enk- or CGRP-IR was reduced. In separate studies, I have shown that sympathetic neurons can influence the expression of NPY in parasympathetic neurons. Following sympathectomy, the percentage of ciliary neurons with NPY-IR was significantly increased. My data provide evidence that each neuropeptide may be regulated separately. Furthermore, I found that the relationships between peptide-IR and mRNA levels for some neuropeptides change during development, suggesting that the regulation of individual peptides is altered during development. It is possible that the mechanisms regulating neuropeptide expression are as diverse as the phenotypes they generate
Bibliographical Information:

Advisor:

School:Case Western Reserve University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:neuropeptidergic phenotypes neuropeptides

ISBN:

Date of Publication:01/01/1993

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