Portal de Periódicos da CAPES

Structure and Action of Nemertine Toxins

1985; Oxford University Press; Volume: 25; Issue: 1 Linguagem: Inglês

10.1093/icb/25.1.99

2162-4445

William R. Kem,

Insect and Pesticide Research

Bacq (1936, 1937) discovered two substances by pharmacological experiments using whole body extracts of various nemertine species. "Amphiporine," found only in hoplonemertines, stimulated nicotinic acetylcholine receptor-mediated events. "Nemertine" evoked spontaneous action potentials in isolated crab nerves. Both substances caused convulsions when injected into crabs. Anabaseine, a pyridine alkaloid isolated from the hoplonemertine Paranemertes peregrina, has chemical and pharmacological properties equivalent to "amphiporine." Hoplonemertines produce a wide variety of pyridine toxins depending on the species. The heteronemertine Cerebratulus lacteus contains cytolytic (10,000 dalton) and neurotoxic (6,000 dalton) proteins. The neurotoxic polypeptides most closely resemble "nemertine": they cause repetitive spiking in isolated crustacean axons. Several cytolytic and neurotoxic "isotoxins" occur within Cerebratulus. Both the hoplonemertine and heteronemertine toxins are localized in the integumentary tissues of the body wall and proboscis. So far, the pyridine alkaloid toxins are only found in the Enoplan species, where they probably function as both offensive and defensive toxins. Protein toxins have only been found in Anoplan species; they probably serve as a chemical defense against some predators.