The Effect of an α2-Adrenoceptor Antagonist (Yohimbine) on Dynamic Autoregulation in the Human Middle Cerebral Artery and Ophthalmic Artery

This study has been completed.
Sponsor:
Information provided by:
Medical University of Vienna
ClinicalTrials.gov Identifier:
NCT00814047
First received: December 22, 2008
Last updated: NA
Last verified: December 2008
History: No changes posted
  Purpose

Blood flow autoregulation is defined as the ability of a tissue to maintain a relatively constant flow, despite moderate alterations in perfusion pressure. Similar to the cerebral, renal, coronary and skeletal muscle circulations, the ocular vascular bed shows the property of flow autoregulation. This homeostatic mechanism allows blood supply to the eye to match metabolic demand during daily activities, such as changes in posture, or in more critical conditions.

Autoregulation has been found to be a complex phenomenon, showing heterogeneity in its site and time course of action. Since metabolic, myogenic, neurogenic and possibly endothelium-related mechanisms may be involved, several factors may vary depending on the challenging stimulus, the vessel tone, or the degree of impairment of autoregulation.

To study the dynamics of ocular autoregulation, it is necessary to introduce a step disturbance (stimulus) in ocular perfusion pressure and to record the responses of ocular blood flow continuously before and after this step disturbance. The investigators have employed a mechanical noninvasive technique to induce an ocular perfusion pressure step disturbance without drugs or changes in the concentration of vasoactive substances in the blood by using the thigh cuff technique inducing a small step decrease in ocular perfusion pressure.

With this technique the investigators could show significant differences in the time response of blood velocities in the ophthalmic and middle cerebral artery. This clearly indicates different mechanisms to be responsible for autoregulatory mechanisms distal to the vessels.

Interestingly our results indicate that in the ophthalmic artery a late vasoconstriction occurs. Many previous investigations have demonstrated that sympathetic nerve stimulation causes vasoconstriction in the ocular circulation. Accordingly, the present study tests the hypothesis that α2-adrenoceptors are involved in the dynamic regulation of blood flow in the ophthalmic and middle cerebral artery after a step decrease in perfusion pressure.


Condition Intervention Phase
Blood Flow Velocity
Autoregulation
Ocular Physiology
Drug: Yohimbine hydrochloride
Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Crossover Assignment
Masking: Double-Blind
Primary Purpose: Treatment
Official Title: The Effect of an α2-Adrenoceptor Antagonist (Yohimbine) on Dynamic Autoregulation in the Human Middle Cerebral Artery and Ophthalmic Artery

Resource links provided by NLM:


Further study details as provided by Medical University of Vienna:

Primary Outcome Measures:
  • Relation between blood pressure and local perfusion parameters.

Estimated Enrollment: 18
  Eligibility

Ages Eligible for Study:   18 Years to 35 Years
Genders Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Men aged between 18 and 35 years
  • Non-smokers
  • Normal findings in medical history and pre-study screening unless the investigator considers an abnormality to be clinically irrelevant
  • Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
  • Normal ophthalmic findings, ametropia < 3 Dpt.

Exclusion Criteria:

  • Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
  • Treatment in the previous 3 weeks with any drug
  • Symptoms of a clinically relevant illness in the 3 weeks before the first study day
  • History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
  • History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with, distribution, metabolism or excretion of study drugs
  • Blood donation during the previous 3 weeks
  Contacts and Locations
Please refer to this study by its ClinicalTrials.gov identifier: NCT00814047

Locations
Austria
Department of Clinical Pharmacology, Medical University of Vienna
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
Investigators
Principal Investigator: Gabriele Fuchsjäger-Mayrl, MD Department of Clinical Pharmacology, Medical University of Vienna
  More Information

No publications provided

Responsible Party: Gabriele Fuchsjaeger-Mayrl, MD, Department of Clinical Pharmacology, Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00814047     History of Changes
Other Study ID Numbers: OPHT-280604
Study First Received: December 22, 2008
Last Updated: December 22, 2008
Health Authority: Austria: Agency for Health and Food Safety

Keywords provided by Medical University of Vienna:
ultrasonography

Additional relevant MeSH terms:
Yohimbine
Adrenergic alpha-2 Receptor Antagonists
Adrenergic alpha-Antagonists
Adrenergic Antagonists
Adrenergic Agents
Neurotransmitter Agents
Molecular Mechanisms of Pharmacological Action
Pharmacologic Actions
Physiological Effects of Drugs
Mydriatics
Autonomic Agents
Peripheral Nervous System Agents

ClinicalTrials.gov processed this record on April 20, 2014