Abstract
The muscarinic agonists pilocarpine and cevimeline are used as sialogogues in treating dry mouth. These drugs also induce drinking behavior though muscarinic receptors in the central nervous system. Pilocarpine and cevimeline were applied by intracerebroventricular (ICV) injection in rats and water intake was measured. By the ICV injection of pilocarpine, water intake was increased in a dose-dependent manner at 0.03-100 nmol. But abnormal behaviors appeared in the concentration of more than 100 nmol. The volume of water intake was 10.8 ± 2.6ml at 100 nmol. By the ICV injection of cevimeline, water intake was also increased in a dose-dependent manner at 10-1000 nmol (2.3 ± 2.0ml at 1000 nmol), but induced drinking was reduced by the over concentration of 3000 nmol. The water intake by the injection of 0.3 nmol pilocarpine and 300 nmol cevimeline were nearly equal (2.3 ± 0.9 ml and 2.1 ± 0.6 ml, for one hour, recepectively). Hence, we compared with time courses of the water intake at these concentration of drugs. By pilocarpine, the peak of water intake appeared at 5 min and finished at 10 min. However, by cevimeline, the peak of water intake appeared at 10 min and the drinking behavior continued for 30 min. The time courses were similar to those of salivary secretion in previous reports (Omori Y. et al. 2003). The results suggest that pilocarpine induces an acute and strong dipsogenic response, but cevimeline induces a long-lasting and weak dipsogenic response. [Jpn J Physiol 54 Suppl:S202 (2004)]
