Capsaicin-induced impairment of tactile spatial discrimination ability in man: indirect evidence for increased receptive fields in human nervous system

The effects of capsaicin was investigated on vibration detection thresholds, touch detection thresholds, mechanically-evoked pain thresholds, two-point discrimination ability, and ability to detect roughness of different stimulation surfaces in the left hands of human volunteers in a double-blind controlled study. Capsaicin cream induced allodynia to mechanical stimulation in both primary and secondary area of hyperalgesia. Capsaicin impaired two-point discrimination ability, and reduced the ability to detect differences of the roughness of various stimulation surfaces only within the capsaicin treated area (area of primary hyperalgesia). These changes were not seen after placebo cream. We conclude that experimental inflammation and related pain impairs spatial discrimination ability which could be due to increases in the receptive fields of neurons in the peripheral and central nervous system (CNS). (C) 1998 Elsevier Science B.V. All rights reserved.