Quantitative study of salivary secretion in Parkinson's disease

We examined basal and reflex salivary flow rate and composition in 46 patients with Parkinson's disease (PD), both in off and on conditions, compared to 13 age-matched controls without underlying disease or treatment affecting autonomic function. Whole saliva was collected 12 hours after withdrawal of dopaminergic drugs and at the peak of levodopa-induced motor improvement. Twenty-three of the 46 PD patients had received domperidone a week before the study. Basal salivary flow rate was significantly lower in PD patients in the off state compared to controls (P<0.005). Levodopa increased salivary flow rate (P<0.05) both in the domperidone-pretreated and untreated groups. Citric acid stimulated salivary flow rate in both the off and on states in PD patients. This effect was higher in the domperidone-pretreated patients. Salivary concentration of sodium, chloride, and amylase was higher in PD patients than in controls and was not affected by levodopa or domperidone treatment. Levodopa stimulates both basal and reflex salivary flow rate in PD. The mechanism appears to be central, as the effect is not blocked by domperidone. Domperidone may have a peripheral effect that potentiates reflex salivary secretion. Salivary composition is abnormal in PD and is not affected by levodopa treatment.