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      Bilateral Superior Cervical Ganglionectomy Increases Choroidal Blood Flow in the Rabbit

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          Abstract

          In this study, we evaluate the effect of bilateral superior cervical ganglionectomy on albino rabbit choroidal blood flow (CBF) in changes of perfusion pressure (PP). Twenty albino rabbits of either sex weighing between 2.0 and 3.0 kg were randomly divided into two groups. The experimental group (group S) included 10 rabbits (20 eyes) that received bilateral superior cervical ganglionectomy one week prior to the study. The other 10 rabbits (20 eyes) served as a control (group N): each received the same procedure as group S except that the superior cervical ganglion was preserved. By means of a laser Doppler flowmeter (Perimed PF4001), blood cell flux (PF), velocity (V), and concentration of moving blood cells (CMBC) were recorded simultaneously while intraocular pressure was increased linearly by a syringe pump. Blood pressure and intraocular pressure were continuously monitored. The laser beam focused on the posterior pole away from major retinal vessels. When PP decreased from 75 to 0 mm Hg, in group N, PF, V and CMBC decreased from 100% to 6.94 ± 0.91%, 8.41 ± 0.87%, and 19.38 ± 1.11%; in group S, it was 17.75 ± 2.58%, 16.78 ± 1.48%, and 34.58 ± 4.42%, respectively. Group S poses higher PF, V, and CMBC than group N while PP decreased gradually. These results indicate that the superior cervical ganglion plays a role in CBF regulation. Bilateral sympathectomy led to a higher PF in the group S rabbits, indicating increased CBF. PF, V, and CMBC remained constant until PP <55 mm Hg demonstrated the existence of CBF autoregulation within a limited perfusion range in both groups. This autoregulation did not change after sympathectomy.

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          Choroidal myogenic autoregulation and intraocular pressure.

          J Kiel (1994)
          This study tests the hypothesis that choroidal myogenic autoregulation participates in the intraocular pressure (IOP) response to mean arterial pressure (MAP) by minimizing arterial-pressure-dependent changes in choroidal blood volume. To test this hypothesis, the IOP response to MAP was quantified before and after impairing choroidal autoregulation. In a previous study, the efficacy of choroidal myogenic autoregulation was inversely related to IOP. Therefore, in one series of experiments (n = 6), the relationship between MAP and IOP was determined at normal and elevated baseline IOP (i.e., 15 and 25 mmHg, respectively). In a second series of experiments (n = 6), the relationship between MAP and IOP was determined at the normal IOP (15 mmHg) before and after administering hydralazine, an arterial vasodilator. In both series, the MAP manipulations were kept brief to avoid the confounding effects of aqueous compensation. The experiments were performed in pentobarbital anesthetized rabbits with hydraulic occluders placed on the thoracic descending aorta and inferior vena cava to raise and lower MAP, respectively. MAP was measured via a central ear artery catheter. The right eye was cannulated with two 23 gauge needles; one cannula was used to set the IOP by varying the ocular volume and the other was used to measure the IOP. The protocol consisted of inflating the occluders to cause brief (1-1.5 min) ramp increases and decreases in MAP over a wide pressure range. Baseline IOP was set prior to each occlusion, but was otherwise uncontrolled. In the first series, the MAP range was 30 to 95 mmHg and IOP changed by 6 mmHg at the normal baseline IOP and by 18 mmHg at the elevated baseline IOP. The corresponding volume shifts were 7.7 and 14.5 microliters, respectively. In the second series, the MAP range was 25 to 95 mmHg and IOP changed by 6 mmHg during control and by 14 mmHg after hydralazine. The corresponding volume shifts were 6.7 and 13.8 microliters, respectively. In both series, the prompt return of IOP to baseline upon restoration of normal MAP indicated that the volume changes were due to changes in ocular blood volume. Additional experiments confirmed that elevating the baseline IOP and administering hydralazine impaired choroidal autoregulation but did not alter the cranial venous pressure response to varying MAP.(ABSTRACT TRUNCATED AT 400 WORDS)
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            Author and article information

            Journal
            OPH
            Ophthalmologica
            10.1159/issn.0030-3755
            Ophthalmologica
            S. Karger AG
            0030-3755
            1423-0267
            2000
            December 2000
            18 October 2000
            : 214
            : 6
            : 421-425
            Affiliations
            Department of Ophthalmology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China
            Article
            27536 Ophthalmologica 2000;214:421–425
            10.1159/000027536
            11054003
            fcae49ec-7b6a-4476-9387-1abf6bc1f766
            © 2000 S. Karger AG, Basel

            Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

            History
            Page count
            Figures: 3, References: 16, Pages: 5
            Categories
            Original Paper · Travail original · Originalarbeit

            Vision sciences,Ophthalmology & Optometry,Pathology
            Autoregulation,Laser Doppler flowmetry,Superior cervical ganglion,Choroidal blood flow

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