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Presynaptic inhibition of primary afferents by depolarization: observations supporting nontraditional mechanisms
Author(s) -
Hochman Shawn,
Shreckengost Jacob,
Kimura Hiroshi,
Quevedo Jorge
Publication year - 2010
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.2010.05436.x
Subject(s) - neuroscience , depolarization , inhibitory postsynaptic potential , afferent , postsynaptic potential , neurotransmission , gabaergic , chemistry , cholinergic , biology , receptor , biophysics , biochemistry
Primary afferent neurotransmission is the fundamental first step in the central processing of sensory stimuli and is controlled by pre‐ and postsynaptic inhibitory mechanisms. Presynaptic inhibition (PSI) is probably the more powerful form of inhibitory control in all primary afferent fibers. A major mechanism producing afferent PSI is via a channel‐mediated depolarization of their intraspinal terminals, which can be recorded extracellularly as a dorsal root potential (DRP). Based on measures of DRP latency it has been inferred that this primary afferent depolarization (PAD) of low‐threshold afferents is mediated by minimally trisynaptic pathways with pharmacologically identified GABAergic interneurons forming last‐order axo‐axonic synapses onto afferent terminals. There is still no “squeaky clean” evidence of this organization. This paper describes recent and historical work that supports the existence of PAD occurring by more direct pathways and with a complex pharmacology that questions the proprietary role of GABA and GABA A receptors in this process. Cholinergic transmission in particular may contribute significantly to PAD, including via direct release from primary afferents.