Chemical anatomy of pain pathways 2.1 Flashcards
Q: What is the primary function of the dorsal horn (DH) of the spinal cord?
A: The DH serves as an important hub for the integration of nociceptive (pain) and innocuous peripheral stimuli and modulates incoming stimuli from descending pathways.
Q: What theory describes the balance between large and small diameter primary afferent fibers in pain signaling?
A: The Gate Control Theory of Pain (GCT) proposed by Melzack and Wall.
Q: What happens when large diameter afferent fibers are activated according to the GCT?
A: They can excite projection cells while also exerting feedforward inhibition, leading to the closure of the gate and blocking transmission of pain signals to the brain.
Q: What is the role of small-diameter nociceptors in the GCT?
A: They activate transmission cells and inhibit the activity of inhibitory interneurons, resulting in the opening of the gate and transmission of pain signals.
Q: What percentage of spinal cord neurons are interneurons?
A: About 99% of spinal cord neurons are interneurons.
Q: What distinguishes excitatory and inhibitory interneurons in the dorsal horn?
A: All excitatory interneurons are glutamatergic, while inhibitory interneurons express GABA, with some being functionally glycinergic.
Q: What is the estimated percentage of inhibitory interneurons in laminae I-II of the mouse spinal cord?
A: Inhibitory interneurons represent about 25% of lamina I-II neurons.
Q: Who conducted a morphological classification of lamina II interneurons?
A: Grudt and Perl.
Q: What are the four main classes of lamina II interneurons identified by Grudt and Perl?
A: Islet cells, central cells, radial cells, and vertical cells.
Q: What neurochemical markers are used to classify inhibitory interneurons in the rat spinal cord?
A: Neuropeptide Y (NPY), galanin (Gal), neuronal nitric oxide synthase (nNOS), and parvalbumin (PV).
Q: Which population of inhibitory interneurons in laminae I-II has been shown to receive monosynaptic input from Aβ fibers?
A: Parvalbumin (PV) neurons.
Q: What neuropeptides are expressed among excitatory interneurons in laminae I-II?
A: Neurokinin B (NKB), neurotensin (NT), gastrin-releasing peptide (GRP), and substance P (SP).
Q: What is the significance of somatostatin (SST) among excitatory neurons in the spinal cord?
A: SST is widely expressed among excitatory neurons, being present in 60% to 90% of cells that express other neuropeptides.
Q: How can interneurons contribute to pain modulation in the dorsal horn?
A: Interneurons can form complex circuits that integrate and process incoming nociceptive and non-nociceptive signals, thus influencing pain perception.
Q: What is a potential therapeutic target for pain control based on the functions of the dorsal horn?
A: The dorsal horn itself, due to its role in integrating nociceptive and innocuous stimuli and modulating pain pathways.
