Pain threshold changes by skin vibratory stimulation in healthy subjects

Abstract

The purpose of this research is to evaluate the changes of cutaneous pain threshold induced by vibratory stimuli applied to the skin. The pain threshold was tested by means of electrical stimuli using the method of limits. Both vibratory stimuli (conditioning stimuli) and electrical stimuli (test stimuli) were driven by a computer. The experiments were carried out on the dorsal surface of the second phalanx of the index finger in the dominant hand of 34 healthy subjects (18 males and 16 females). The conditioning stimuli were sinusoidal waves (250 microm peak to peak) at a rate of 30 and 300 Hz. During the experiment (6 min of vibration and 9 min after) the cutaneous temperature of the stimulated area was recorded. Both vibratory rates induced significant increases of the pain threshold but the 30 Hz vibrations were the more effective. After stimulation the pain threshold lowered to a steady value which was higher than before the start of vibrations. Such threshold changes showed no correlation throughout the experiment with changes in skin temperature. We therefore advance the hypothesis that the main factors which modulate the pain threshold are neuronal connections between tactile and pain pathways.

Syringe micro vibrator (SMV) a new device being introduced in dentistry to alleviate pain and anxiety of intraoral injections, and a comparative study with a similar device

“…Blair [32] recommended the use of VibraJect ® for painless injection. In contrast, Yoshikawa et al [33] found no significant pain reduction when VibraJect ® was applied with a conventional dental syringe.…”

An inhibitory interaction of human cortical responses to stimuli preferentially exciting Aδ or C fibers

“…Electrophysiological investigations reveal both inhibitory and excitatory postsynaptic responses of nociresponsive dorsal horn neurons, including inhibitory interactions mediated through the activation of Aδ and C fibers (Christensen and Perl, 1970;Chung et al, 1984a;Chung et al, 1984b;Traub and Mendell, 1988;Yoshimura and Jessell, 1989;Tsuruoka et al, 1990;Schneider and Perl, 1994;Shimizu et al, 1995;Sandkuhler et al, 1997;Liu et al, 1998). Subsequent human neurophysiological and psychophysical studies revealed the well-known suppressive effect of tactile and vibrotactile stimulation on various forms of pain and pain-related evoked responses (Melzack and Wall, 1965;Zoppi et al, 1991;Marchand et al, 1991;Kakigi and Shibasaki, 1992;Akyuz et al, 1995;Svensson et al, 1999;Watanabe et al, 1999;Hoshiyama and Kakigi, 2000;Nahra and Plaghki, 2003) but the opposite interaction has been demonstrated also (Apkarian et al, 1992;Apkarian et al, 1994;Tran et al, 2003). Earlier human neurophysiological studies provided evidence that the activation of Aδ-fibers suppresses the cortical response mediated by C-fibers (Bromm and Treede, 1987a;Bromm and Treede, 1987b).…”

In-phase Chest Wall Vibration Decreases Dyspnea During Arm Elevation in Chronic Obstructive Pulmonary Disease Patients.

“…It has been shown that skin vibration increases pain threshold (15). However, if sensory system sensitivity reduction was the principal reason for the decrease in AEdyspnea, a similar effect could have occurred for AEmuscle fatigue.…”