Effects of Intramuscular (IM) Oxytocin on Pupil Diameter and Heart Rate Variability (HRV)

Phase 4

Completed

Conditions: Chronic Pain Due to Injury

Interventions: Drug: Oxytocin
Drug: Placebo

Registration Number: NCT04105998

Lead Sponsor: Wake Forest University Health Sciences

Brief Summary: The goal of this study is to test the effects of oxytocin on heart rate variability and pupil diameter, both of which have subtle effects on the activity rate of the autonomic nervous system.

Detailed Description: This protocol focuses on two measures of autonomic control to quantify central actions of oxytocin. First, the study team proposes to examine the influence of oxytocin on heart rate variability with focus on its effect on high frequency variability, most commonly ascribed to parasympathetic nervous system activity acting to brake sympathetic tone. Intranasal oxytocin has been demonstrated to have a large effect size on this measure which can be repeated at frequent intervals. As a secondary assessment of parasympathetic activity, the study team will measure low frequency fluctuation in pupil diameter, termed hippus, which also reflects parasympathetic nervous system activity. This outcome measure can be assessed in 3 seconds using equipment currently being used under Institutional Review Board (IRB) approved protocols.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 22

Inclusion Criteria

Male or female > 18 and < 66 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.
Previous eye surgery, eye medications, cataracts

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Placebo, Then Oxytocin	Placebo	Subjects in this arm will receive intramuscular injection of (1 milliliter) saline at the first visit. Then at the next visit, they will receive Intramuscular injection of Oxytocin (Pitocin®), 10 International Units (IU).
Oxytocin First, then Placebo	Placebo	Subjects in this arm will receive Intramuscular injection of Oxytocin (Pitocin®), 10 International Units (IU) at the first visit. Then at the next visit, they will receive Intramuscular injection of (1 milliliter) saline.
Oxytocin First, then Placebo	Oxytocin	Subjects in this arm will receive Intramuscular injection of Oxytocin (Pitocin®), 10 International Units (IU) at the first visit. Then at the next visit, they will receive Intramuscular injection of (1 milliliter) saline.
Placebo, Then Oxytocin	Oxytocin	Subjects in this arm will receive intramuscular injection of (1 milliliter) saline at the first visit. Then at the next visit, they will receive Intramuscular injection of Oxytocin (Pitocin®), 10 International Units (IU).

Primary Outcome Measures

Name	Time	Method
Fluctuation in Pupil Diameter (Hippus) -Post Drug Administration	For 120 minutes after study drug administration	Magnitude of power at the dominant frequency in the Fourier transform of pupil diameter in the .1-2 Hz range, termed hippus. Pupil measurements will be made for 20 seconds every 5 minutes until 120 minutes after study drug administration. The Fast Fourier Transform (FFT) essentially takes what looks like a random, noisy signal and distills it into a combination of many sine waves, each with different frequencies and different sizes (think ocean waves, which has the big wave we see and the small up and down wavelets on the top of the water). The primary outcome measure is the size of the largest wave in the frequency range above in this FFT analysis. Its dimensions are milliseconds\^2.
Fluctuation in Pupil Diameter (Hippus) -Pre Drug Administration	From 20 minutes before until study drug injection	Magnitude of power at the dominant frequency in the Fourier transform of pupil diameter in the .1-2 Hz range, termed hippus. Pupil measurements will be made for 20 seconds every 5 minutes for 20 minutes. The Fast Fourier Transform (FFT) essentially takes what looks like a random, noisy signal and distills it into a combination of many sine waves, each with different frequencies and different sizes (think ocean waves, which has the big wave we see and the small up and down wavelets on the top of the water). The primary outcome measure is the size of the largest wave in the frequency range above in this FFT analysis. Its dimensions are milliseconds\^2.
Heart Rate Variability in the High Frequency Range	For 120 minutes after study drug administration	Magnitude of peak power in the 0.12-0.40 Hz frequency range of the Fast Fourier Transform of heart rate. The Fast Fourier Transform (FFT) essentially takes what looks like a random, noisy signal and distills it into a combination of many sine waves, each with different frequencies and different sizes (think ocean waves, which has the big wave we see and the small up and down wavelets on the top of the water). The primary outcome measure is the size of the largest wave in the frequency range above in this FFT analysis. Its dimensions are milliseconds\^2.