Pain Perception and the Autonomic Nervous System

Influences of the Autonomic Nervous System on Experimental Pain Sensitization

In this study, we want to investigate how pain processing and sensation are related to a certain part of the nervous system, the so-called autonomic nervous system.

For this purpose, we apply heat and pressure stimuli to the skin and test pain processing by means of ratings scales and sensory tests. Breathing, heart rate and sweat response are also measured. To assess the spinal cord level, we measure muscle response (measured by electromyography, EMG) to electrical stimulation. Additionally, sensory nerves will be stimulated at the ear and participants will also be given various questionnaires to complete.

This study investigates the effects of autonomic regulation on pain perception and experimentally induced pain sensitivity. Participants come for one or two study visits, that will last approximately 3 hours. The study is divided into two phases: the pilot phase and the main experimental phase.

During the pilot phase, the perception of pressure and heat stimuli, as well as spinal excitability, will be assessed before and during different types of electrical stimulation of sensory nerves at the outer ear.

During the main experimental phase, skin sensitivity and spinal excitability will be assessed before and after repetitive heat stimulation and stimulation of sensory nerves at the outer ear.

In both study phases, the activity of the autonomic nervous system will be assessed throughout the experiment, and questionnaires will be completed.

Inclusion Criteria:

1. Over 18 and below 40 years of age
2. Good general health
3. Able to give informed consent

Exclusion Criteria:

1. Any major medical or psychiatric condition (e.g. heart disease, diabetes, autoimmune disorders, infectious diseases, major depressive disorder), any chronic pain condition, any respiratory problems, any acute pain at time of study
2. Inability to follow study instructions, e.g. due to language problems
3. Pregnancy (female participants will be asked if pregnancy could be possible)
4. Increased alcohol (>2 (for women)/4 (for men) standard glasses per day or >5 (for women)/4 (for men) glasses at least once a month within a few hours) or caffeine consumption (≥ 400mg per day)
5. Consumption of alcohol, drugs, analgesics within the last 24 h
6. Consumption of more than 100 mg of caffeine within the last 8 h
7. Scar tissue or generally reduced sensitivity in the designated testing site areas
8. Shoe size < 38 (if experiment is conducted at the feet)
9. History of cardiovascular disease or carotid artery disease
10. Medication or Substances inferring with the autonomic nervous system or with pain sensitivity (e.g. Benzodiazepines, Nicotine)