Effect of PG-SPI and PG-KII, two novel and natural tachykinins, on salivary secretion in the rat

In an in vivo study of salivation in rats, the scialogogic effects of two natural and amphibian tachykinins, PG-SPI and PG-KII, which activate distinct tachykinin receptors, were compared with those of the tachykinins substance P, neurokinin A and B, and kassinin. The rank order of potencies of these peptides injected intravenously on salivation was: PG-SPI = SP greater than or equal to PG-KII = KASS > NKA >> NKB. Atropine (1 mg/kg, IV) had no effect on PG-SPI-, SP-, and NKA-induced salivation, but reduced that stimulated by PG-KII and KASS. We conclude that PG-SPI and PG-KII increase salivary secretion through different mechanisms and that rat salivary glands contain PG-SPI- and PG-KII-sensitive receptors.