What is the sudomotor axon reflex?
Sudomotor axon reflex employs the same mechanism as the skin axon-reflex flare, but the neural pathway consists of an axon reflex mediated by the postganglionic sympathetic axon (C fibers) that innervates sweat glands.
The axon terminals of these fibers are activated by the local injection of ACh: the generated impulse travels to a branch point where it is deflected and then travels orthodromically to activate a different sweat gland, releasing ACh, which binds to M3 muscarinic receptors.
In other words, in the sudomotor axon reflex, the activation of sweat glands results in the reflex activation of another population of nearby glands, the sweat output of which can be quantitatively measured.
The QSART is, therefore, a sensitive and reproducible test of the integrity of the postganglionic sympathetic sudomotor axon.
