Background
Cutaneous autonomic function can be quantified by the assessment of sudomotor and vasomotor responses. Although piloerector muscles are innervated by the sympathetic nervous system, there are at present no methods to quantify pilomotor function.
Objective
To quantify piloerection using phenylephrine hydrochloride in humans.
Design
Pilot study.
Setting
Hospital-based study.
Participants
Twenty-two healthy volunteers (18 males, 4 females) aged 24 to 48 years participated in 6 studies.
Interventions
Piloerection was stimulated by iontophoresis of 1% phenylephrine. Silicone impressions of piloerection were quantified by number and area. The direct and indirect responses to phenylephrine iontophoresis were compared on both forearms after pretreatment to topical and subcutaneous lidocaine and iontophoresis of normal saline.
Results
Iontophoresis of phenylephrine induced piloerection in both the direct and axon reflex–mediated regions, with similar responses in both arms. Topical lidocaine blocked axon reflex–mediated piloerection post-iontophoresis (mean [SD], 66.6 [19.2] for control impressions vs 7.2 [4.3] for lidocaine impressions; P < .001). Subcutaneous lidocaine completely blocked piloerection. The area of axon reflex–mediated piloerection was also attenuated in the lidocaine-treated region postiontophoresis (mean [SD], 46.2 [16.1] cm2 vs 7.2 [3.9] cm2; P < .001). Piloerection was delayed in the axon reflex region compared with the direct region. Normal saline did not cause piloerection.
Conclusions
Phenylephrine provoked piloerection directly and indirectly through an axon reflex–mediated response that is attenuated by lidocaine. Piloerection is not stimulated by iontophoresis of normal saline alone. The quantitative pilomotor axon reflex test (QPART) may complement other measures of cutaneous autonomic nerve fiber function.