NEUROPEPTIDES IN THE SALIVA OF HEALTHY-SUBJECTS

Five neuropeptides: Substance P (SP), Neurokinin A (NKA), Calcitonin G ene-Related Peptide (CGRP), Neuropeptide Y (NPY) and Vasoactive Intest inal Polypeptide (VIP), were measured in the saliva of eight subjects. The saliva was collected using different stimulation techniques: whol e resting saliva, whole paraffin stimulated saliva, whole citric acid stimulated saliva and parotid saliva,of different secretion rates - 0. 25 mL/min, 0.50 mL/min and 1.00 mL/min, also stimulated by citric acid . The neuropeptides were analysed by radioimmunoassay. The results sho wed that the concentration of all neuropeptides decreased significantl y, two- to four-fold (CGRP up to 16-fold) in whole saliva, when the sa livary secretion rates increased six- to eight-fold due to stimulation . However, the amounts of all neuropeptides released over time into th e whole saliva increased two- to five-fold (ten-fold for CGRP) as the volumes of saliva increased due to 'chewing-stimulation as compared to resting saliva or citric acid stimulated saliva. There was also more CGRP in the resting saliva than in the citric acid stimulated saliva. The concentration of CGRP in the parotid saliva decreased three- to te n-fold when the salivary now increased, whereas the concentration of N KA increased three- to four-fold and that of NPY almost two-fold under the same conditions. The concentrations of SP and VIP did not change in the different flows of parotid saliva. The release of all neuropept ides in the parotid saliva over time showed significant increases (3-1 4-fold) when the secretion rates increased except CGRP, which showed n o changes at all. We concluded that neuropeptides are continuously rel eased into the saliva. Their amounts increase with stimulation, but th ey are diluted by the increased volume of saliva, and they are also af fected by the mode of stimulation - muscular activity leads to a great er release than citric acid stimulation. As the neuropeptides play an important role in the control of salivary secretory mechanisms, their normal occurrence and release are of fundamental importance for the un derstanding of the function of the salivary glands.