Effects of Intramuscular Oxytocin on Sensory Function in Healthy Volunteers With Ultraviolet Burn Injury to the Skin

Effects of Intramuscular Oxytocin on Sensory Function in Healthy Volunteers With Ultraviolet Burn Injury to the Skin

Effects of Intramuscular Oxytocin on Sensory Function in Healthy Volunteers With Ultraviolet Burn Injury to the Skin

This study proposes to evaluate the effects that a dose of oxytocin given by intramuscular (IM) injection (into the muscle) will have on an area of skin that has been exposed to ultraviolet (UV) light. The area of skin exposed to UV light will have a mild sun burn feeling. Sensory testing will be performed on the area of UV burn. The area will be evaluated for sensitivity in 3 methods: touch, vibratory

This protocol aims to provide an estimate of effect size of intramuscular oxytocin on a test of Aβ and of Aδ fiber sensitivity in injured skin following ultraviolet B (UVB) burned skin. For the primary goal - to examine the effects of oxytocin peripheral nerves after tissue injury - the investigators chose the controlled ultraviolet sunburn model. The investigators propose a randomized, blinded, cross over design with treatment with oxytocin one day and placebo on another. Following baseline measures on each of the two study days, participants will receive an intramuscular injection of oxytocin (Pitocin®) in its indicated dose of 10 IU (17 μg) or an equivalent volume of saline. In order to determine the highest frequency that Aβ nerve fibers can respond to, the investigators will use a device that produces an oscillatory / vibratory stimulus which can be used on the hand. Pain threshold to punctate stimulation within the area of irradiation will be determined using calibrated von Frey filaments and an up-down sequential method which efficiently estimates median thresholds. Thermal heat testing will also be performed by the surface of the skin of the forearm or leg is heated to 45°C using a computer controlled thermode for a period of 5 minutes.

Participant, Investigator and outcomes assessor will be blinded. Research Pharmacist will prepare the study medication administration and hold the randomization.

Intramuscular injection of oxytocin (Pitocin®), 10 IU on the first study day and of 1 ml saline placebo on the second study day

Intramuscular injection of 1 ml saline placebo on the second study day and of oxytocin (Pitocin®), 10 IU on the second study day

Vibration frequency detection threshold in the burned area after IM Oxytocin or placebo injection will be obtained by the subject placing the forearm area that was exposed to the UV burn on the oscillatory device and informing the investigators when the first perception of vibration is felt. A recording of the frequency (1 kilo Hertz to 1 Hertz) will be documented.

Change in Pain Threshold (the Point Where Pain is First Perceived) to a Punctate Mechanical Stimulus After IM Injection.

Verbal pain punctate stimulus detection threshold (the point where pain is first perceived) in the burned area after IM Oxytocin or Placebo injection will be obtained by using von Frey filaments (small filaments that are similar to a paint brush bristle). The skin will be touched with the filaments and the participant will state when pain is perceived and the size of the filament will be documented.

Hypersensitivity in the burned area after IM Oxytocin or placebo injection will be obtained by using a von Frey filament (small filament that is similar to a paint brush bristle). The skin will be touched with the filament and the participant will state when sensitivity is perceived and the area marked and measured in centimeters squared.

Change in Vibration Frequency Detection of Fixed Frequency (When Vibration is First Felt) After IM Injection

Vibration frequency detection of a fixed frequency (256 Hertz) in the burned area after IM Oxytocin or placebo injection will be obtained. The subject will place the wrist area that was exposed to the UV burn on the oscillatory device, the fixed vibratory frequency will begin and will be increased in intensity and the subject will inform the investigators when the first perception of vibration is felt. A recording of the intensity level will be documented in Hertz.

Verbal pain scores (0 to 10; 0 is equivalent to no pain and 10 is equivalent to the worst pain imaginable) to 45 degree Celsius temperature after IM Oxytocin or placebo injection.

Verbal pain scores (0 to 10; 0 is equivalent to no pain and 10 is equivalent to the worst pain imaginable) to 40 degree Celsius temperature applied to the site of the UV burn after IM Oxytocin or placebo injection.

Verbal pain scores (0 to 10; 0 is equivalent to no pain and 10 is equivalent to the worst pain imaginable) to 45 degree Celsius temperature applied to the calf (lower leg) after IM Oxytocin or placebo injection.

Inclusion Criteria: Male or female > 18 and < 60 years of age, Body Mass Index (BMI) <40 Generally in good health as determined by the Principal Investigator based on prior medical history Normal blood pressure and resting heart rate without medication Exclusion Criteria: Hypersensitivity, allergy, or significant reaction to any ingredient of Pitocin® Any disease, diagnosis, or condition (medical or surgical) that, in the opinion of the Principal Investigator, would place the subject at increased risk Women who are pregnant (positive result for serum pregnancy test at screening visit), women who are currently nursing or lactating, women that have been pregnant within 2 years. Neuropathy, chronic pain, diabetes mellitus, or taking benzodiazepines or pain medications on a daily basis.