Mechanism of Action of Tachykinins in the Frog Adrenal Gland

The term tachykinins (TKs) designates a family of neuropeptides that share the common carboxyl-terminal amino acid sequence Phe-X sub(aa)-Gly-Leu-Met-NH sub(2). These peptides are widely represented in the animal kingdom and exert multiple effects on the nervous and immune systems as well as on exocrine and endocrine glands. Immunohistochemical and biochemical studies have revealed the occurrence of various members of the TK family in the adrenal gland of mammals and amphibians. Although TKs have been shown to stimulate steroid secretion from rat, bovine, and frog adrenal tissue, the mechanism by which TKs exert their corticotropic effect remains poorly understood. Here, we report the mode of action of these peptides in the adrenal gland of the frog Rana ridibunda.