Specific uptake and retrograde flow of antibody to dopamine-β-hydroxylase by central nervous system noradrenergic neurons in vivo

Abstract

This study sought to determine whether the administration in vivo of antibody to dopamine-β-hydroxylase (ADβH) is taken up by central noradrenergic neurons and transported by retrograde flow to the cell bodies of origin. ADβH serum or pre-immune serum (control) in volumes of 1–20 μl were stereotaxically injected into the lateral ventricle. Rats were sacrificed at times ranging from 1 h to 8 days. Cryostat sections were stained with fluorescein conjugated IgG. After 24 h, a bilateral granular fluorescence was seen only in neuronal cell bodies corresponding to noradrenergic cell groups A 1–A 7 with the most intense fluorescence localized within perikarya and processes of the locus coeruleus (A 6) and subcoeruleus. This technique also permitted the visualization of the ascending dorsal and ventral noradrenergic bundles as well as varicose fibers and terminals in a pattern identical to that reported with hitofluorescence, autoradiographic, biochemical and classical immunofluorescence techniques for the identification of noradrenergic fiber distributions. At 3 and 6 h, the first detectable fluorescence was observed in forebrain noradrenergic terminals and in fibers of the dorsal and ventral noradrenergic bundles. At 10 h fluorescent varicosities were first visualized within the caudal dorsal bundle and some cytoplasmic fluorescent particles were seen within locus coeruleus cell bodies. After 18 h locus coeruleus and subcoeruleus cell bodies were heavily stained, whereas medullary noradrenergic cell groups and nerve fibers were not labeled until after 24 h. An intense locus coeruleus fluorescence remained for 3 days and was completely absent after 6 days. Bilateral transection of the dorsal noradrenergic bundle in the rostral mesencephalon, at the time of injection, effectively blocked the retrograde transport of fluorescing material to the locus coeruleus. The overall staining pattern suggests that, in vivo, central noradrenergic fibers are capable of taking up antibody to dopamine-β-hydroxylase. The ability of a dorsal bundle transection to abolish locus coeruleus staining, as well as the time course of ADβH staining in noradrenergic neurons, suggests that AD/gbH is transported via a rapid retrograde flow process. This technique combines retrograde transport of a marker protein with the sensitivity and specificity of immunocytochemical procedures to provide a new tool for the neuroanatomical study of neurotransmitter systems.