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Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles
PURPOSE: Brimonidine is an imidazoline compound used for the treatment of glaucoma, but having very little effect on pupil diameter. Like para-aminoclonidine, most imidazoline compounds interact with postsynaptic α-adrenoceptors and cause pupil dilatation. Therefore, as part of an investigation of t...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Dove Medical Press
2016
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4869645/ https://www.ncbi.nlm.nih.gov/pubmed/27274189 http://dx.doi.org/10.2147/OPTH.S100755 |
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author | Tatsui, Sonoko Ishikawa, Hitoshi Shimizu, Kimiya Mashimo, Kimiyo |
author_facet | Tatsui, Sonoko Ishikawa, Hitoshi Shimizu, Kimiya Mashimo, Kimiyo |
author_sort | Tatsui, Sonoko |
collection | PubMed |
description | PURPOSE: Brimonidine is an imidazoline compound used for the treatment of glaucoma, but having very little effect on pupil diameter. Like para-aminoclonidine, most imidazoline compounds interact with postsynaptic α-adrenoceptors and cause pupil dilatation. Therefore, as part of an investigation of the mechanism of action of brimonidine on pupil diameter, the present study was initiated to measure, in vitro, the relative potency of brimonidine on the pre- and postsynaptic α-adrenoceptors of rabbit iris dilator muscle. METHODS: The contractile activity of brimonidine and its effect on twitch contraction evoked by electrical field stimulation were studied in isolated rabbit iris dilator muscles by isometric tension recording. RESULTS: Brimonidine significantly inhibited the twitch contraction of the dilator muscle caused by field stimulation, without affecting the response to exogenously applied phenylephrine. Compared to phenylephrine, brimonidine caused only a small contractile response with % maximum contraction values of <10%. CONCLUSION: These results suggest that brimonidine may act on nerve endings to inhibit adrenergic neurotransmission with very little effect on postsynaptic α-adrenoceptors. This may indicate that brimonidine reduced the pupil diameter just a little, thus improving night vision. |
format | Online Article Text |
id | pubmed-4869645 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2016 |
publisher | Dove Medical Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-48696452016-06-07 Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles Tatsui, Sonoko Ishikawa, Hitoshi Shimizu, Kimiya Mashimo, Kimiyo Clin Ophthalmol Original Research PURPOSE: Brimonidine is an imidazoline compound used for the treatment of glaucoma, but having very little effect on pupil diameter. Like para-aminoclonidine, most imidazoline compounds interact with postsynaptic α-adrenoceptors and cause pupil dilatation. Therefore, as part of an investigation of the mechanism of action of brimonidine on pupil diameter, the present study was initiated to measure, in vitro, the relative potency of brimonidine on the pre- and postsynaptic α-adrenoceptors of rabbit iris dilator muscle. METHODS: The contractile activity of brimonidine and its effect on twitch contraction evoked by electrical field stimulation were studied in isolated rabbit iris dilator muscles by isometric tension recording. RESULTS: Brimonidine significantly inhibited the twitch contraction of the dilator muscle caused by field stimulation, without affecting the response to exogenously applied phenylephrine. Compared to phenylephrine, brimonidine caused only a small contractile response with % maximum contraction values of <10%. CONCLUSION: These results suggest that brimonidine may act on nerve endings to inhibit adrenergic neurotransmission with very little effect on postsynaptic α-adrenoceptors. This may indicate that brimonidine reduced the pupil diameter just a little, thus improving night vision. Dove Medical Press 2016-05-11 /pmc/articles/PMC4869645/ /pubmed/27274189 http://dx.doi.org/10.2147/OPTH.S100755 Text en © 2016 Tatsui et al. This work is published and licensed by Dove Medical Press Limited The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. |
spellingShingle | Original Research Tatsui, Sonoko Ishikawa, Hitoshi Shimizu, Kimiya Mashimo, Kimiyo Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title | Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title_full | Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title_fullStr | Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title_full_unstemmed | Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title_short | Pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
title_sort | pre- and postsynaptic effects of brimonidine on isolated rabbit iris dilator muscles |
topic | Original Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4869645/ https://www.ncbi.nlm.nih.gov/pubmed/27274189 http://dx.doi.org/10.2147/OPTH.S100755 |
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