Parasympathetic varicosity proliferation and synaptogenesis in rat eyelid smooth muscle after sympathectomy

Brain Research
P G Smith, F Marzban

Abstract

Parasympathetic innervation to eyelid smooth muscle inhibits sympathetic neurotransmission pre-junctionally without appreciable direct post-junctional effects. However, 5 weeks after sympathectomy, parasympathetic stimulation elicits substantial cholinergically mediated contractions. This study examined ultrastructural changes accompanying the conversion to parasympathetic excitation. In intact muscles, 64+/-9 nerve varicosities were encountered per 104 micron2. Most were close to muscle cells and not fully enclosed by supporting cells. Axo-axonal synapses were observed occasionally. Two days following sympathectomy, varicosity numbers were reduced by 97% and, relative to controls, remaining varicosities were farther from muscle cells and more frequently fully enclosed by supporting cells, but contained greater numbers of small spherical and large dense vesicles. By 6 weeks post-sympathectomy, numbers of varicosities per unit muscle volume increased to 14% of controls. These varicosities differed from those at 2 days in being closer to smooth muscle cells, less frequently enclosed, and having fewer small vesicles. These findings indicate that intact eyelid smooth muscle varicosities are predominantly sympathetic, but a small nu...Continue Reading

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Citations

Dec 9, 2000·Autonomic Neuroscience : Basic & Clinical·E V Zoubina, P G Smith
Mar 26, 2002·Autonomic Neuroscience : Basic & Clinical·Peter G SmithWohaib Hasan
Dec 21, 2000·The European Journal of Neuroscience·W Hasan, P G Smith
May 23, 2002·The Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society·Analía RicheriM Mónica Brauer

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