The peptides and precursors thereof, inclusive salts thereof, of the present invention are useful as a pharmaceutical composition, for example as therapeutic or prophylactic agents for hormone-producing tumors, acromegaly, gigantism, dementia, gastric ulcer and the like, hormone secretion inhibitors, tumor growth inhibitors, neural activity or sleep modulators, etc. The DNAs coding for the peptides or precursors of the invention are useful as a pharmaceutical composition, for example as agents for the gene therapy or prevention of hormone-producing tumors, acromegaly, gigantism, dementia, gastric ulcer and the like, hormone secretion inhibitors, tumor growth inhibitors, neural activity or sleep modulators, etc. Furthermore, the DNAs coding for the peptides or precursors of the invention are useful as agents for the gene diagnosis of various diseases, for example, hormone-producing tumors, acromegaly, gigantism, dementia, gastric ulcer, etc. The antibodies against the peptides, precursors or salts of the invention can be used for assaying the peptides, precursors or salts of the invention in test solutions. The peptides, precursors or salts of the invention are useful as reagents for screening for compounds, or salts thereof, capable of modifying the binding of the peptides, precursors or salts of the invention to certain receptors.