Assessment of Peripheral GABA Receptors for Local Pain Relief

Study Overview
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Brief Summary
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The effect of peripheral GABAA receptor activation on pain and sensitivity in healthy human subjects has never been investigated. However, as earlier studies suggest that activation of peripheral GABAA receptors is anti-nociceptive in rats, it is important to determine if these findings can be translated into human subjects to determine if peripheral GABAA receptors are a viable target for future analgesic drug development.

Detailed Description
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Subproject I This study will test if oral administration of GABA containing solutions will reduce the pain and sensitivity induced by application of capsaicin to the tongue of healthy human subjects. Thirty, pain-free men (n=15) and women (n=15) for the oral cavity study. Subproject II This study will test the hypothesis that intramuscular injection of GABA alone will not be painful, but will reduce muscle pain sensitivity in healthy human subjects. Thirty, pain-free men (n=15) and women (n=15) will be recruited for the intramuscular GABA injection studies Subproject III This study will test the hypothesis that intramuscular injection of GABA with glutamate will decrease the intensity of glutamate-evoked muscle pain in healthy human subjects. Thirty, pain-free men (n=15) and women (n=15) will be recruited for the intramuscular glutamate and GABA injection studies.

Official Title
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Vurdering af Perifere GABAA-receptorer Med Henblik på Lokal Smertelindring

Conditions
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Pain

Intervention / Treatment
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* Drug: GABA oral solution
* Drug: Intramuscular GABA
* Drug: Pain modulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged 20-40 years Free from ongoing or chronic pain Adequate conversational English Exclusion Criteria: Pregnancy or intent to become pregnant, breast feeding Signs or symptoms of any serious systemic diseases Current malignancies High blood pressure Requirement for chronic administration of psychiatric, analgesic or other medications that might influence their response to pain Frequent recreational drug or alcohol use Previous neurologic, musculoskeletal or mental illnesses Lack of ability to cooperate

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: GABA oral solution<br>This study will test if oral administration of GABA containing solutions will reduce the pain and sensitivity induced by application of capsaicin to the tongue of healthy human subjects. | Drug: GABA oral solution<br>* Oral mouth wash containing either GABA, lidocaine or distilled water will be used to decrease burning tongue pain produced by capsaicin<br>* Other names: capsaicin;|
| Experimental: Intramuscular GABA<br>This study will test the hypothesis that intramuscular injection of GABA alone will not be painful, but will reduce muscle pain sensitivity in healthy human subjects. | Drug: Intramuscular GABA<br>* The effect of intramuscular injection of GABA or lorazepam will be compared with buffered isotonic saline<br>* Other names: buffered isotonic saline;|
| Experimental: Pain modulation<br>This study will test the hypothesis that intramuscular injection of GABA with glutamate will decrease the intensity of glutamate-evoked muscle pain in healthy human subjects. | Drug: Pain modulation<br>* The effect of GABA alone or in combination with lorazepam on muscle pain produced by intramuscular injection of glutamate will be assessed.<br>* Other names: lorazepam;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain Intensity Rating | visual analogue scale | continuously for 95 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Jaw Function Tests | maximal jaw opening, maximal bite force | every 5 min for 50 minutes | 
| Quantitative Sensory testing | Pressure detection and pain threshold, thermal detection and pain threshold | every 10 min for 90 min | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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craniofacial pain, masticatory muscle, burning mouth syndrome, temporomandibular disorders