Response of human oral mucosa and skin to histamine provocation: laser Doppler perfusion imaging discloses differences in the nociceptive nervous system

Abstract

Objective. To investigate the existence of histamine-excitable nerve fibers in the oral mucosa and to compare the response to histamine provocation in healthy volunteers with that in a small group of patients with chronic oral pain. Material and methods. Thirteen healthy volunteers and six patients suffering from chronic oral pain took part in the study. Blood perfusion was monitored in the hard palate, the tongue, and the skin of the cheek using laser Doppler perfusion imaging (Perimed; Sweden). Baseline scannings were performed, followed by 15 scannings after iontophoresis of histamine (1%). A free description of the sensations was then obtained from the participants after finishing the measurements. Results. Compared to pre-histamine scanning, histamine application resulted in a considerable increase in blood perfusion in all regions (p<0.001) that was significantly higher in skin than in oral mucosa (p<0.001). There were no significant differences between the healthy volunteers and the patients regarding baseline blood flow, increased blood perfusion, or flare size after histamine provocation. The sensory impression was reported to be more persistent and intense in the skin than in the oral mucosa. No effect on mucosa could be detected by visual inspection. Conclusions. Intra-oral flare could be induced by activating histamine-excitable nerve fibers. Both duration and intensity of the flare were considerably less pronounced than in the control skin site. Histamine application was not clearly associated with itch.

• Axon reflex
• histamine-excitable nerve fibers
• laser-Doppler perfusion imaging
• nociceptors
• oral pain