Chemical anatomy of pain pathways 1.1 Flashcards
What is the function of DRG neurons?
DRG neurons provide sensory innervation to the body (excluding the head) and are responsible for transmitting information from peripheral tissues to the central nervous system (CNS).
What are nociceptors and how are they classified?
Nociceptors detect noxious (potentially harmful) stimuli. They are classified into two main subtypes: Adelta (thinly myelinated) fibers, which respond to mechanical/thermal stimuli, and unmyelinated C-fibers, which respond to chemical, thermal, or polymodal stimuli.
What are the four modalities of nociceptors?
A-delta thermal nociceptors
C-fiber thermal nociceptors
Chemically sensitive nociceptors
Polymodal nociceptors
What is the significance of neurochemical markers in DRG neurons?
Neurochemical markers allow the identification of specific subpopulations of DRG neurons, helping to understand their roles in different types of pain pathways (e.g., peptidergic vs non-peptidergic neurons).
What are peptidergic and non-peptidergic C-fibers?
Peptidergic C-fibers express neuropeptides such as CGRP and substance P, while non-peptidergic fibers bind to isolectin B4 (IB4). Both subtypes are involved in nociception, but they mediate different aspects of pain.
What percentage of C-fibers are peptidergic and non-peptidergic?
Approximately 50% of C-fibers are peptidergic (CGRP+), and 50% are non-peptidergic (IB4+).
Why is it important to classify DRG neurons into subtypes?
Understanding the subtypes of DRG neurons helps target specific populations for pain management. It allows for more precise treatment strategies in chronic pain, especially when considering different roles in peripheral and central mechanisms.
How do peripheral nociceptors contribute to pain despite ‘pain being in the mind’?
Peripheral nociceptors initiate the pain signal, and blocking their activity (e.g., through nerve blocks) can reduce or abolish pain in chronic conditions like phantom limb pain, highlighting their essential role in pain pathways.
What challenges exist in current DRG neuron classification systems?
Current classifications fail to accurately distinguish between subpopulations with distinct morphology, biochemistry, and functions, though new approaches (like RNA sequencing) are providing better insights.
What did Clifford Woolf’s 2014 study reveal about DRG neuron subsets?
Woolf’s study showed that different DRG neuron subsets have heterogeneous expression of voltage-gated and TRP channels, indicating functional diversity even within seemingly similar groups.
What were the key findings of Usoskin et al.’s 2014 study on DRG neurons?
Usoskin et al. identified 11 distinct clusters of DRG neurons, including five subgroups of nociceptors. This study provided more precise classification, especially distinguishing peptidergic and non-peptidergic neurons into further subtypes.
Why are recent advances in DRG neuron classification significant for pain management?
New classification methods, such as RNA sequencing, can help identify more specific subpopulations of nociceptors, which may lead to targeted therapies for chronic pain conditions that are more effective and have fewer side effects.
