Should Skin Biopsies Be Performed in Patients Suspected of Having Parkinson’s Disease?

Figure 2

Illustration of the vasomotor axon reflex. Iontophoresis of acetylcholine induces vasodilation in the “direct” skin region of application via receptor activation. Consequently, an action potential emerges in the afferent nerve innervating this vessel. This potential travels in an orthodromic fashion to an axonal branch point where it switches to another vasomotor fiber. Upon antidromic conduction, the action potential reaches terminal nerve endings adjacent to a neighboring population of blood vessels. From these terminals, vasoactive substances are released to cause “indirect” vasodilation in a skin region which is surrounding the region of iontophoresis. Consecutive enhancement of blood flow relates to functional integrity of the stimulated vasomotor nerve fiber. Similarly, the axon reflex can be evoked in sympathetic adrenergic pilomotor and sympathetic cholinergic sudomotor fibers. Figure designed by Dr. Siepmann and Dr. Illigens.