Coexistence and plasticity of neurotransmitters and neuropeptides in the rat iris.
The presence, distribution and origin of substance P (SP), neuropeptide Y (NPY), and CGRP-immunoreactive axons in rat iris were investigated in whole mount preparations, with special respect to the localization of the "classical" adrenergic and cholinergic ground plexuses. SP-IR fibres are distributed parallel to the pupillary margin in the sphincter muscle, and in an irregular plexus in the dilator muscle. The distribution of CGRP-IR fibres was similar to this. Both SP- and CGRP-IR elements originated from the Gasserian ganglion. Following electrocoagulation of the ophthalmic nerve, both SP- and CGRP-IR nerves completely disappeared, while in the caudal nucleus of the trigeminal nerve a substantial decrease of the immunoreactivity was found. NPY-IR fibres have also been demonstrated in the anterior uvea, displaying a pattern similar to that of the adrenergic nerves. In the sympathectomized iris, there was a marked decreased in the density of NPY-IR fibres indicating that NPY most likely coexists with the classical sympathetic neurotransmitter, noradrenalin in the sympathetic nerve supply deriving from the superior cervical ganglion. 1 month after sympathectomy, there was an increase in the density (and possibly also in the number) of both SP- and CGRP-IR fibres in the denervated iris. Subsequent immuno-electron microscopic analysis has demonstrated that both SP- and CGRP-IR fibres are unmyelinated axons, embedded in a common Schwann cell cytoplasm together with a number of axons devoid of immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Vereczkey
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Department of Anatomy, Albert Szent-Györgyi Medical University, Szeged, Hungary.
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis; D005260:Female; D007498:Iris / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D009412:Nerve Fibers / Q000502:physiology / Q000648:ultrastructure; D009478:Neuropeptide Y / Q000032:analysis; D009479:Neuropeptides / Q000032:analysis*; D018377:Neurotransmitter Agents / Q000032:analysis*; D009900:Optic Nerve / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000032:analysis
D009478:Neuropeptide Y; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide