title: Appearance of the noradrenergic markers tyrosine hydroxylase and neuropeptide Y in cholinergic nerves of the iris following sympathectomy.
abstract: Selective autonomic denervations of the iris have been used to study the possible redistribution of adrenergic markers within adult nerve fiber systems and to reveal the cellular origin of a nonsympathetic fiber plexus induced to express such markers. The presence and distribution of fibers showing neuropeptide Y (NPY)- and tyrosine hydroxylase (TH)-like immunoreactivity was studied in the rat iris using stretch-prepared whole mounts. Normal irides contained a dense regular network of NPY-positive varicose fibers. Such fibers were regularly seen innervating blood vessels. The choroid membrane had a high number of fluorescent fibers. A similar, although slightly denser TH-positive fiber system was visualized in the iris. One or 2 days after surgical removal of the superior cervical ganglion, almost all NPY- and TH-positive fibers had disappeared, suggesting that most, if not all, NPY-positive fibers in the iris originate in the superior cervical ganglion. In irides from long-term sympathectomized animals, a high number of TH- and NPY-immunoreactive fibers had reappeared, while such irides were devoid of catecholamine-containing fibers, as evidenced by Falck-Hillarp histochemistry. The appearance of TH- and NPY-positive fibers in sympathetically denervated irides was clearly time dependent. The distribution of fluorescent fibers in irides from intact and sympathectomized animals showed obvious dissimilarities such as a lower fluorescence intensity and fewer varicose fibers in denervated irides. Furthermore, in irides from sympathectomized rats, TH- and NPY-positive fibers were not associated with blood vessels. Unilateral removal of the parasympathetic ciliary ganglion, which supplies the iris with cholinergic fibers, 3 days prior to sacrifice in animals bilaterally sympathectomized 1 month earlier, led to a drastic reduction in numbers of TH- and NPY-positive iris fibers on the ciliarectomized/sympathectomized side as compared to the sympathectomized-alone side. The present experiments thus suggest that adult cholinergic neurons in vivo are capable of expressing adrenergic characteristics under experimental conditions.
authors.forename: H
authors.initials: H
authors.lastname: Björklund
authors.forename: T
authors.initials: T
authors.lastname: Hökfelt
authors.forename: M
authors.initials: M
authors.lastname: Goldstein
authors.forename: L
authors.initials: L
authors.lastname: Terenius
authors.forename: L
authors.initials: L
authors.lastname: Olson
mesh_terms: D000320:Adrenergic Fibers / Q000032:analysis / Q000648:ultrastructure*; D000818:Animals; D002462:Cell Membrane / Q000032:analysis; D002799:Cholinergic Fibers / Q000032:analysis / Q000648:ultrastructure*; D002829:Choroid / Q000032:analysis; D002924:Ciliary Body / Q000032:analysis; D003714:Denervation; D005260:Female; D005455:Fluorescent Antibody Technique; D007498:Iris / Q000032:analysis* / Q000294:innervation; D008297:Male; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009478:Neuropeptide Y; D051381:Rats; D013562:Sympathectomy; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis*
chemical_list: D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D014446:Tyrosine 3-Monooxygenase