Kinetic assessment of salivary secretory response to citric acid, as compared with pilocarpine

Background: Induction of salivation is becoming increasingly popular in the assessment of salivary gland status. Various mechanical or pharmacological procedures are empirically used to produce salivation. Oral stimulation by citric acid (AC) is by far the most used sialagogue procedure. Aim: To cha racterize the salivary secretory response to AC solutions applied to the do rsolateral tongue surfaces. Subjects and methods: Young healthy women from the upper levels of a medical career (n=19) participated as volunteers. Sal ivary volume and UV-absorbing organic material in saliva from single subjec ts were measured after various protocols of topical stimulation by AC. Resu lts: After a single stimulation by 1-8% AC the salivary flow rate peaked be fore 30 seconds and records the basal level earlier than 2 minutes. Repetit ive stimulations at 30-sec intervals kept the flow rate at a maximum. After suspending these stimulations, basal flow rate was recovered before 2 minu tes. Repetitive AC-stimulations at 8-min intervals produced a series of ide ntical and independent secretory responses. The concentration of organic ma terial in saliva remained unaltered after the various modes of stimulation. Thus, the profile of organic material secretion was always a direct expres sion of changes in salivary flow rate. In contrast to AC, the oral administ ration of the cholinergic agonist pilocarpine (PIL) produced a two-wave sal ivary response that as a whole lasted for about 30 ones secreted in respons e to AC. Conclusions: AC provoked a rapid and short-lived salivary response that differs markedly from the one produced by other secretagogues, like p ilocarpine.