The present study examines the mechanism(s) of action of anethole trithione (Sulfarlem S25) compared to the sialogogue pilocarpine. The chronic effects (7 days of treatment) of anethole trithione, pilocarpine and/or amitriptyline on autonomic receptor binding (homogenates) were measured together with parallel tests of stimulation-induced rises in delta [Ca2+]i in collagenase-isolated rat parotid acini. The results revealed that chronic treatment with amitriptyline resulted in significantly increased rises in delta [Ca2+]i after stimulation with 20 microM of carbachol or adrenaline, and a significant increase in muscarinic acetylcholine receptor density. In addition, anethole trithione also increased cholinergic and adrenergic responsiveness. The double treatment of amitriptyline and anethole trithione or amitriptyline and pilocarpine did, however, prevent the rise in delta [Ca2+]i observed under conditions when these drugs were administered alone. Furthermore, anethole trithione, but not pilocarpine, was able to prevent the amitriptyline-induced upregulation in muscarinic acetylcholine receptor density. In conclusion, the experimental data presented in this study are compatible with the hypothesis that anethole trithione might stimulate some post-receptor effect in the coupling to the secretory response. In addition, this study supports the beneficial effects of anethole trithione in treating drug-induced xerostomia.