The influence of sensory stimulation (acupuncture) on the release of neuropeptides in the saliva of healthy subjects

In recent studies we have shown that xerostomia (dry mouth) can be treated successfully with sensory stimulation (acupuncture). The increase of saliva secretion lasted often for at least one year. Some neuropeptides have been found to influence the secretion of saliva. The aim of this study was to investigate the mechanisms behind the effect of acupuncture on salivary secretion by measuring the release of neuropeptides in saliva under the influence of sensory stimulation. VIP-like immunoreactivity (VIP-LI), NPY-LI, SP-LI, CGRP-LI and NKA-LI were analysed in the saliva of eight healthy subjects. Manual acupuncture and acupuncture with low-frequency electrical stimulation (2 Hz) were used. The saliva was collected during 20 minutes before the start of acupuncture stimulation, then during 20 minutes while the needles were in situ and then for another 20 minutes after the needles were removed. Four different saliva sampling techniques were used: whole resting saliva, whole saliva stimulated by paraffin-chewing, whole saliva stimulated by citric acid (1%), and parotid saliva, also stimulated with citric acid (1%). The results showed significant increases in the release of CGRP, NPY and VIP both during and after acupuncture stimulation, especially in connection with electro-acupuncture. SP showed only few increases, mainly in connection with electro-acupuncture, whereas NKA generally was unaffected by the acupuncture stimulation. The sensory stimulation-induced increase in the release of CGRP, NPY and VIP in the saliva could be an indication of their role in the improvement of salivary flow rates in xerostomic patients who had been treated with acupuncture.