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Trial registered on ANZCTR


Registration number
ACTRN12611000820909
Ethics application status
Not yet submitted
Date submitted
3/08/2011
Date registered
4/08/2011
Date last updated
31/08/2011
Type of registration
Prospectively registered

Titles & IDs
Public title
The acute effects of Yohimbine on fear conditioning and the neural processing of emotional images, and on delayed extinction learning and memory for the images.
Scientific title
An Analysis of Sex Differences in the Effects of Yohimbine on Fear Conditioning and on the Encoding of Emotional Memory in Healthy Participants: A Randomised Placebo-Controlled Trial
Secondary ID [1] 262765 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Healthy subjects, investigating the mechanisms underpinning Post Traumatic Stress Disorder 270475 0
Condition category
Condition code
Mental Health 270632 270632 0 0
Studies of normal psychology, cognitive function and behaviour

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Healthy male and female participants are either given Yohimbine (20mg) or placebo pill via oral administration. Participants then undergo a fear acquisition paradigm in which they will be shown images of blue and red circles. In a counter-balanced order, one set of coloured circles will be paired with a mild electrical stimulus applied to participants' fingertips at an intensity selected by the participant to be "uncomfortable but not painful". Skin conductance will be used as a measure of conditioned response to the stimuli. Participants will then
undergo a functional magnetic resonance imaging scan (fMRI) where they will view emotional and neutral images. They return two days later to complete surprise recall and recognition memory tasks for the images. At this second session, participants will also undergo a fear extinction paradigm in which they will be presented with the blue and red circles without aversive reinforcement. Skin conductance will again be recorded during this procedure.
Intervention code [1] 267108 0
Treatment: Drugs
Comparator / control treatment
Participants are given one placebo pill and undergo the same fear conditioning procedure and fMRI paradigm in which they view emotional and neutral images. These control participants also return two days after the scan for the delayed memory tests and fear extinction procedure. The placebo pill will be identical in appearace and taste to the Yohimbine pill. They will be made of Vitamin E, and thus do not contain any active ingredients.
Control group
Placebo

Outcomes
Primary outcome [1] 269359 0
After drug adminstration via oral pills, we will compare the neural activation across the whole brain (with particular focus on the amygdala, hippocampus and medial prefrontal regions) between participants' processing of emotional and neutral images. Neural activation will be assessed through blood oxygenated level dependent (BOLD) contrasts obtained from functional magnetic resonance imaging (fMRI).
Timepoint [1] 269359 0
Functional magnetic resonance imaging scanning will take place approximately one hour after the administration of the drug(s) or placebo. During the scanning, participants will view blocks of five images at a time (each image will be presented for five seconds). In total 25 negative and 25 neutral images will be presented for a total scanning duration of approximately six minutes (allowing for fixation or baseline measures of BOLD activity).
Primary outcome [2] 269360 0
We will assess participants' delayed memory for the emotional and neutral images, and relate memory performance to neural activation recorded during the processing of the images.
Memory will firstly be assessed through a recall task, in which participants are given 15 minutes to recall and write as many details about the images as they can. An independent rater will then total the number of accurate responses for emotional and neutral images for an overall indication of free recall performance.
Recognition memory will then be assessed via a computer task in which participants will be shown a set of familiar images (i.e. viewed during the scan two days prior) and novel images. The participants must respond 'Yes' or 'No' to whether they recognise the image. Again, a total score will be calculated for the number of emotional and neutral images correctly recognised for each participant.
Timepoint [2] 269360 0
Exactly two days after the drug administration and fMRI procedure.
Primary outcome [3] 279540 0
We will assess participants' rate of fear conditioning across trials. More specifically, five red and five blue circles will be presented for 8 seconds each in a habituation phase. Following this, in the conditioning phase of the experiment, five red and five blue circles will be presented for 8 seconds each and either the red or the blue circles (randomly selected) will be followed immediately by a 500ms mild electrical stimulus. Skin conductance in response to the presentation of each coloured circle will be recorded across trials as a measure of conditioning.
Timepoint [3] 279540 0
The fear conditioning paradigm will occur approximately 45 minutes after ingestion of Yohimbine (20mg) or placebo pill, and will occur immediately before the fMRI paradigm detailed above in Primary outcome 1.
Secondary outcome [1] 279449 0
Whether there are individual difference variables that are related to memory performance. Individual difference variables of interest include the capacity to vividly visualise images in the mind (measured through administration of the Vividness of Visual Imagery Questionnaire); the tendency to suppress thoughts (measured via the White Bear Suppression Inventory), and; level of Depressive symptoms (measured via the Depression and Anxiety Scale, version 21).
Timepoint [1] 279449 0
Individual difference measures will be completed immediately prior to drug administration.
Secondary outcome [2] 287869 0
Extinction learning during testing session 2 will also be assessed. Participants will undergo an extinction paradigm in which they will presented with ten blue and ten red circles without any accomanying mild electrical stimulus. Skin conductance response across trials will be compared for the coloured circles that were previously paired with the electrical stimulus (the CS+) and the coloured circles that were not (the CS-).
Timepoint [2] 287869 0
The extinction learning procedure will occur immediately after the delayed memory tests during testing session 2.

Eligibility
Key inclusion criteria
Healthy University Students.
Right handed.
Minimum age
18 Years
Maximum age
40 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Current course of medication (including hormonal contraceptive for female participants), pregnancy or breasfeeding, substance abuse / dependence, current or recent history of psychiatric conditions, current or recent medical conditions, suicidal thoughts, known sensitivity to Hydrocortisone or Yohimbine, post-menopausal (for female participants), any participants with metal implants in the body. Participants are instructed not to drink alcohol or take any illegal drugs on the day of drug administration, and to abstain from fluids and food for two hours prior to drug administration.

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation concealment will be conducted by labelling drug containers from 1 - 100.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation will be done by using a randomization table created by a computer software (i.e. computerised sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?



Intervention assignment
Parallel
Other design features
All subjects, medical personnel and site investigators are blind to the drug condition.
Phase
Phase 4
Type of endpoint/s
Safety/efficacy
Statistical methods / analysis

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
1/02/2012
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
120
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
Recruitment postcode(s) [1] 4334 0
2052

Funding & Sponsors
Funding source category [1] 269590 0
University
Name [1] 269590 0
University of New South Wales
Country [1] 269590 0
Australia
Primary sponsor type
University
Name
University of New South Wales
Address
University of New South Wales
Kensington
NSW 2052
Country
Australia
Secondary sponsor category [1] 266621 0
None
Name [1] 266621 0
Address [1] 266621 0
Country [1] 266621 0
Other collaborator category [1] 252167 0
Hospital
Name [1] 252167 0
Royal North Shore Hospital
Address [1] 252167 0
Royal North Shore Hospital
Reserve Road
ST LEONARDS NSW 2065
Country [1] 252167 0
Australia

Ethics approval
Ethics application status
Not yet submitted
Ethics committee name [1] 269542 0
Northern Sydney Central Coast HREC (Hawkesbury)
Ethics committee address [1] 269542 0
Ethics committee country [1] 269542 0
Date submitted for ethics approval [1] 269542 0
12/09/2011
Approval date [1] 269542 0
Ethics approval number [1] 269542 0

Summary
Brief summary
This study aims to examine sex differences in the effects of Yohimbine on the neural processing of, and delayed memory for, emotional images. Sex differences will also be explored in the effects of Yohimbine on fear conditioning, and whether this impacts the rate of extinction learning after a delay. Participants will be randomly assigned to recieve either Yohimbine or Placebo. Participants will first undergo a fear conditioning procedure in which they will be presented with coloured circles and a particular colour will be paired with a mild electrical stimulus. Rate of conditioning (or associative fear learning) will be measured via skin conductance responses across trials. Subsequently, in an fMRI scanning machine, all participants will view a series of emotional and neutral images.
Two days later, participants will return and undergo a surprise memory test for the images. Following the memory tests, participants will undergo an extinction learning procedure in which skin conductance will be recorded across trials in which the same circles will be presented without any reinforcement (electrical stimulus).
The hypothesis is that Yohimbine will enhance amydgala activation during the processing of emotional images, and be associated with superior memory for the emotional images. It is predicted that Yohimbine will enhance the rate of fear conditioning, particularly in women. It is also predicted that the administration of Yohimbine will result in strong amygdala activation during the processing of emotional images as well as the deactivation of prefrontal regions of the brain in participants with higher levels of endogenous cortisol. Finally, it is believed that participants in the Yohimbine group will experience a slower rate of extinction learning after the delay (and particularly in women). All participants and research staff will be blind to the drug contition of the subject until after the study is completed.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 32969 0
Address 32969 0
Country 32969 0
Phone 32969 0
Fax 32969 0
Email 32969 0
Contact person for public queries
Name 16216 0
Ms Jacinta Wassell
Address 16216 0
School of Psychology,
University of New South Wales
Kensington, NSW 2052
Country 16216 0
Australia
Phone 16216 0
+61 405 265 886
Fax 16216 0
Email 16216 0
[email protected]
Contact person for scientific queries
Name 7144 0
Ms Jacinta Wassell
Address 7144 0
School of Psychology,
University of New South Wales
Kensington, NSW 2052
Country 7144 0
Australia
Phone 7144 0
+61 405 265 886
Fax 7144 0
Email 7144 0
[email protected]

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No Supporting Document Provided



Results publications and other study-related documents

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