Modulation of Pain

Introduction

• Equally important as pain pathway.
• Related to the spinothalamic tract and anterolateral system.
• Focuses on endogenous systems, meaning the body's internal processes to inhibit pain.

Types of Pain Modulation

1. Gate Control Theory
2. Descending Analgesic System

Gate Control Theory

• An analogy: Bumping head = pain activation via A-delta and C-fibers.
• Rubbing affected area activates touch receptors, reducing pain perception.
• Pathway of C-fibers:
  • Painful stimulus activates peripheral and central processes.
  • C-fibers go to Rexed Lamina II (substantia gelatinosa of Rolando).
  • C-fibers release Substance P, modulating slow pain.
  • A-delta fibers release glutamate for fast pain modulation.

Mechanism

• Activation of touch receptors by rubbing leads to:
  • Stimulation of dorsal column fibers.
  • Collaterals stimulate inhibitory neurons releasing GABA.
  • GABA inhibits pain pathway at the spinal cord, reducing pain perception.

Descending Analgesic System

• Involves multiple brain structures like:
  • Periaqueductal Gray Matter (PAG)
  • Periventricular Gray Matter (PVG)
  • Locus Coeruleus
  • Reticular Formation
  • Raphe Nucleus Magnus

Mechanism

• Structures send descending fibers to spinal cord, controlling pain.
• Neurotransmitters involved:
  • Locus Coeruleus: Norepinephrine
  • Raphe Nucleus Magnus and Reticular Formation: Serotonin
• These transmitters act on inhibitory neurons which release natural opioids (e.g., enkephalins, endorphins, dynorphins) reducing pain perception.

Activation

• Spino-mesencephalic fibers from the anterolateral system stimulate structures during pain.
• Higher brain structures (limbic nuclei, sensory cortex) influence activation.

Conclusion

• Understanding pain modulation helps in managing and reducing pain perception.
• The body's natural systems use neurotransmitters and endogenous opioids to regulate pain.

• Note: Check related videos and resources for deeper understanding of specific pathways and structures.