Neuromuscular blocker found, often in very large quantities, in the median zone of the hypobranchial body of Murex trunculus and of other related species of mollusks: Erspamer, Dordoni, Ric. Sci. Ricostr. 16, 1114 (1946); Arch. Int. Pharmacodyn. 74, 263 (1947); Erspamer, ibid. 76, 308 (1948). Isoln: idem, Experientia 4, 226 (1948); M. Roseghini et al., Eur. J. Biochem. 12, 468 (1970); J. E. Blankenship et al., Comp. Biochem. Physiol. 51C, 129 (1975). Synthesis: Pasini et al., Ann. 578, 6 (1952); Pasini, Coda, US 2956061 (1960 to Società Farmaceutici). Structure: V. Erspamer, O. Benati, Science 117, 161 (1953). Effect on vertebrate and invertebrate muscles: J. C. de Freitas, Comp. Biochem. Physiol. 56C, 57 (1977).