Abstract
Pilocarpine, a muscarinic receptor agonist, is a typical sialagogue to treat hyposalivation. Although peripherally applied pilocarpine makes the oral cavity wet by increasing saliva, it is well-known in animal experiments that it also induces water intake. Mechanisms underlying the relationships between these events are unknown. Intracerebroventricularly injected pilocarpine induced water intake but not salivary secretion. Intracerebroventricularly applied atropine, a muscarinic receptor antagonist, suppressed the increased water intake by the intraperitonially and intracerebroventricularly applied pilocarpine. We tested which parts of brain were involved in these responses by using c-Fos immunohistochemistry. Intraperitonially injected pilocarpine increased the number of c-Fos immunopositive cells in some nuclei of the circumventricular organs, hypothalamus and medulla, which are related to thirst sensation. Intracerebroventricularly applied atropine suppressed the increased number of c-Fos immunopositive cells by the intraperitonially and intracerebroventricularly applied pilocarpine. We conclude that peripherally injected pilocarpine affects the parotid glands and the thirst center in the central nervous system. [J Physiol Sci. 2007;57 Suppl:S135]
