Parotid Salivary Response to Clonidine in Tourette's Syndrome: Indicator of Adrenergic Responsivity

The cell membranes of the acinar cells in the parotid gland contain both α-adrenergic receptors (which regulate the volume of saliva and the release of potassium ions) and β-adrenergic receptors (which regulate the secretion of amylase). We used parotid salivary volume and amylase secretion as indicators of adrenergic functioning in 11 young male patients with Tourette's syndrome (TS). Parotid saliva was collected for 1 hour before and 4 hours following placebo or a single dose of clonidine (0.05–0.15 mg) in five drug-free TS patients and in six TS patients who had shown good therapeutic responses to long-term clonidine treatment. Following placebo, drug-free patients showed increased salivary volume and total amylase secretion over a 4-hour collection period. Clonidine produced decreased salivary volume for both the drug-free (-63% decrease) and chronically treated patients (-56%). Also, following a single dose of clonidine, 5/6 of the chronically treated patients and 1/3 of the drug-free patients showed decreased salivary amylase concentration; all showed decreased total secretion of amylase. Untreated TS patients may experience nor-adrenergic hyper-reactivity to stressful situations. Clonidine inhibits noradrenergic functioning in TS patients even after treatment for up to 4 years.