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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...

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Autores principales: Tatsui, Sonoko, Ishikawa, Hitoshi, Shimizu, Kimiya, Mashimo, Kimiyo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Dove Medical Press 2016
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.
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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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