Acts as a mitogenic factor for embryonic neurons in the sympathetic nervous system. Has powerful hypotensive and vasodilatory effects. Behaves either as a circulating hormone or as a neurotransmitter. Stimulates cAMP production in rat peritoneal macrophages. Inhibits the growth of human small-cell lung carcinoma (SCLC) both in vitro and in vivo, suggesting that it may be useful as a less toxic alternative to conventional chemotherapeutic agents in the treatment of SCLC. Nitric oxide stimulates the release of this peptide.