Substance P-like immunoreactivity and analgesic effects of vibratory stimulation on patients suffering from chronic pain.

By applying vibratory stimulation to patients suffering from pain, it is possible to set up an inhibitory control on the pain pathways which is based on the activation of large-sized afferent fibres. The exact mechanisms responsible for these analgesic effects still remain to be determined, however. For this purpose, we investigated in the present study whether or not the analgesic effects were accompanied by a decrease in the CSF substance P-like immunoreactivity levels (SPLI) of seven patients suffering from chronic pain, who were fitted with a ventriculo-peritoneal drain. The SPLI levels were determined before and after 30-min vibratory stimulation sessions. The results show that the SPLI levels decreased as the result of the vibration, but this decrease seems to be too slight to account for the pain relief obtained.