NCT07409753·Phase 2·INTERVENTIONAL

Effects Of Intravenous Oxytocin On Peripheral Sensory Afferents Using Microneurography

Oxytocin Pain Recruiting

Status

Recruiting

Phase

Phase 2

Enrollment

Locations

Results

Not posted

Publications

Study summary

What the protocol is testing.

The goal of this clinical trial is to learn if oxytocin reduces pain in a small area of skin after pulses of non-burning heat by changing how nerves in the heated area react to pressing a thin, bendable plastic bristle and a thick, non-bending plastic bristle in adult, healthy participants. The man questions it aims to answer are: Does oxytocin increase the number of times a fiber which normally responds only to the thin bristle fires (sends a signal) after the heat pulses. Does oxytocin raise the number of times a fiber which normally responds only to the thick bristle fires (sends a signal) after the heat pulses. Researchers will compare oxytocin to a placebo (a look-alike substance that contains no drug) to see if oxytocin ABC works to change how nerves react to light touch and painful pressing in an area of sensitized skin. Participants will: Receive an intravenous injection of oxytocin or placebo on one occasion On the same day, a needle will be put near nerve fibers to record their firing before and after a few cycles of short heating of the skin.

Full detailed description

This protocol will utilize a randomized, triple-masked study design to compare intravenous (IV) oxytocin to placebo on peripheral nerve response to acute pain sensitization in healthy volunteers. Equal numbers of adult men and women; ages 18-65 will be recruited. Participants, recruited from the regional community will report to the Linköping University Neurophysiologic Research Laboratory (Linköping, Sweden) for a 2-hour visit to complete eligibility screening, informed consent, pregnancy and drug use laboratory tests, and questionnaires regarding drug and alcohol use, and receive training in the tests to be used on the study day. On a subsequent study day, participants will come initially to the Linköping University Medical Center where an IV catheter will be inserted and they will receive either IV oxytocin (20 IU) or an equal volume of placebo. Study drug will be randomized and administered in two 30-minute infusions separated by the minutes. Rapid rates of oxytocin infusion can cause acute adverse events in the first minutes of infusion. Although these adverse events rapidly resolve despite continuing the infusion, one event (facial flushing) could negate the blind of study personnel. For that reason, the first infusion will be given at 2 rates, a very slow rate for the first 5 minutes and a greater rate for the remaining 25 minutes. This has been demonstrated to reduce the incidence of facial flushing with oxytocin to a rate similar to placebo. Participants will be continuously monitored for vital signs and intermittently queried for any subjective sensations or adverse events during infusion. After study drug infusion is complete, the IV catheter will be removed and the participant accompanied to the Linköping University Neurophysiologic Research Laboratory, adjacent to the Medical Center, where they will complete psychologic questionnaires and cognitive tests and undergo sensory testing of the skin on the arm of brushing using a computer controlled, robotic system. Then, a 200 micrometer tungsten electrode will be inserted in the radial or peroneal nerve under real-time ultrasound guidance and manipulated until a single nerve fiber and its area of skin innervation (receptive field) are identified. The nerve fiber will be categorized by its speed of conduction and firing pattern to a variety of non-noxious and noxious sensory stimuli to the receptive field. A temperature controlled thermode will be placed on the skin adjacent to and overlapping with the receptive field and acute inflammation induced by 10-second cycles of heating the probe to 50°C with 10 seconds at a non-noxious temperature (30°C) between each heat pulse for a total of 2 minutes. The response of the nerve fiber to noxious and non-noxious stimuli will be repeated. The primary analysis will compare fiber firing in response to a fixed intensity punctate stimulus in the fiber's receptive field between oxytocin and placebo and will be performed separately on touch-sensitive fibers (fast conducting, low threshold mechanoreceptors (A-LTMRs)) and pain-sensitive fibers (fast conducting, low threshold mechanoreceptors (A-HTMRs)). Based on numerous studies performed in rodents at Wake Forest University School of Medicine, we hypothesize that acute heat-induced inflammation will render A-LTMRs less responsive to a touch punctate stimulus and A-HTMRs more responsive to a noxious punctate stimulus and that both of these effects will be reduced by at least 50% in participants who receive IV oxytocin. If such results are obtained, they will challenge the existing paradigm that reduction in pain threshold (allodynia) after sensitization from peripheral injury is driven by increased A-LTMR input and support further exploration for the mechanisms by which oxytocin returns changes in touch and pain fibers towards normal to treat pain.

Interventions

Treatment arms and agents.

DRUG

Intravenous Oxytocin

Intravenous oxytocin, 20 IU will be administered via two 30-minute infusions separated by 30 minutes

DRUG

Intravenous Placebo

Intravenous placebo will be infused in the same volume and timing as the intravenous oxytocin intervention

Timeline

From registration to results.

First posted
Feb 13, 2026
Study start
Oct 22, 2025
Primary completion
Jun 1, 2027
Study completion
Jun 8, 2027
Results posted
Not reported
Registry updated
Feb 13, 2026

Outcomes