The effect of the tachykinin dodecapeptide kassinin, which has been extracted from the skin of several African frogs, on somatostatin release was examined in the rat and compared with that of the neuropeptide substance P. Equimolar doses of the two peptides were injected intravenously and the animals killed at specified intervals after injection. Somatostatin was measured by a specific radioimmunoassay. Kassinin and substance P had no effect when given in low doses (0.1 and 1.0 μg). However, when administered in a dose of 10.0 μg, both peptides significantly increased plasma somatostatin, by 31 and 22% respectively. These findings suggest that kassinin and substance P have common endocrine actions. The effect on somatostatin release may be specific for tachykinins, since other neuropeptides such as the enkephalins have no effect.
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