Related Experiment Video
Updated: Jun 5, 2026
06:04
Intracerebroventricular Treatment with Resiniferatoxin and Pain Tests in Mice
Published on: September 2, 2020
Transient inflammation-induced ongoing pain is driven by TRPV1 sensitive afferents
Alec Okun1, Milena DeFelice, Nathan Eyde
1Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA.
Molecular Pain
|January 12, 2011
Summary
Inflammation causes transient ongoing pain and persistent hypersensitivity, driven by TRPV1-positive fibers. Understanding these early post-injury mechanisms can lead to new pain relief strategies.
Area of Science:
- Neuroscience
- Pain Research
- Pharmacology
Background:
- Tissue injury causes both hypersensitivity to stimuli and ongoing, spontaneous pain.
- Previous work showed pain relief acts as a reward in nerve-injured rats.
- This study investigates inflammation-induced ongoing pain's temporal and mechanistic features.
Purpose of the Study:
- To differentiate the time course and mechanisms of ongoing pain versus evoked hypersensitivity after inflammation.
- To identify the specific nerve fibers and receptors involved in inflammation-induced ongoing pain.
Main Methods:
- Complete Freund's Adjuvant (CFA) induced inflammation in rats.
- Assessed thermal hyperalgesia, guarding behavior, and conditioned place preference (CPP).
- Utilized spinal clonidine, peripheral lidocaine nerve block, resiniferatoxin (RTX), and a TRPV1 antagonist (AMG9810).
Main Results:
- CFA induced thermal hyperalgesia and guarding behavior, persisting for at least 4 days.
- Spinal clonidine produced CPP 1 day post-CFA but not 4 days, while blocking hyperalgesia at both times.
- Peripheral lidocaine blocked ongoing pain, indicating afferent fiber involvement.
- RTX blocked hyperalgesia, ongoing pain, and guarding behavior, implicating TRPV1-positive fibers.
- TRPV1 antagonism (AMG9810) reversed hyperalgesia but not ongoing pain or guarding.
Conclusions:
- Inflammation causes distinct transient ongoing pain and persistent evoked hypersensitivity.
- Ongoing pain is mediated by peripheral input from TRPV1-positive fibers.
- TRPV1 receptor antagonism does not alleviate ongoing pain.
- Investigating afferent fiber excitation mechanisms offers novel pain relief strategies.
Related Concept Videos
01:25Analgesia and Pain Management
Pain is critical to various clinical pathologies, provoking an urgent need for effective management. Pain, whether acute or chronic, is a complex neurochemical process. Its alleviation depends on the type, with nonopioid analgesics effective for mild to moderate pain, such as musculoskeletal or inflammatory pain, while neuropathic pain responds best to anticonvulsants, tricyclic antidepressants, or serotonin/norepinephrine reuptake inhibitors. For severe acute or chronic pain, opioids may be...
01:25Acute Inflammation III: Local and Systemic Effects
Acute inflammation produces a coordinated set of local and systemic changes that limit injury, eliminate pathogens, and initiate repair. These responses arise within minutes of infection, trauma, or chemical insult and are driven by vascular alterations and leukocyte-derived mediators. When the stimulus resolves, the reaction typically abates within days.Local EffectsAt the site of injury, arteriolar vasodilation increases blood flow, resulting in redness and warmth. Simultaneously, increased...
01:44Nociception
Nociception—the ability to feel pain—is essential for an organism’s survival and overall well-being. Noxious stimuli such as piercing pain from a sharp object, heat from an open flame, or contact with corrosive chemicals are first detected by sensory receptors, called nociceptors, located on nerve endings. Nociceptors express ion channels that convert noxious stimuli into electrical signals. When these signals reach the brain via sensory neurons, they are perceived as pain. Thus, pain helps the...
01:43Thermosensation
Peripheral thermosensation is the perception of external temperature. A change in temperature (on the surface of the skin and other tissues) is detected by a family of temperature-sensitive ion channels called Transient Receptor Potential, or TRP, receptors. These receptors are located on free nerve endings. Those detecting cold temperatures are closer to the surface of the skin than the nerve endings detecting warmth. These thermoTRP channels, while temperature selective, have relatively...
01:26Acute Inflammation I: Inflammatory Response
Acute inflammation is a rapid, short-lived physiological response to tissue injury or infection, designed to eliminate harmful agents and initiate repair. This tightly regulated process typically lasts from minutes to several days and is triggered by factors such as microbial invasion, physical trauma, or chemical injury.Recognition and Mediator ReleaseThe inflammatory response begins when resident immune cells—such as mast cells, macrophages, and dendritic cells—detect damage-associated...
01:20Pain
Pain serves as a critical warning signal that alerts the body to potential or actual harm. When mechanical pressure on the skin is intense, such as from a sharp pinch, the sensation transitions from touch to pain. Similarly, extreme temperatures, like a hot pot handle, convert the sensation of heat into pain. Pain can also result from overstimulation of other senses, such as blinding light, loud noise, or the intense heat from habañero peppers. This ability to sense pain is essential for...