Neurotoxins

Neurotoxins are among the agents that can act at nicotinic acetylcholine receptors (nAChR). Protein neurotoxins from the venom of poisonous snakes such as cobras, kraits (see photo at right), mambas, and sea snakes target nicotinic receptors in mammalian muscle and some nicotinic receptors in the nervous system. These toxins cover the acetylcholine or nicotinic binding sites on receptors, preventing acetylcholine or nicotine from inducing the channel to open.

In the wild, such toxins delivered to a mammal diffuse to the diaphragm. There they block nicotinic receptors that receive chemical signals from the phrenic nerve and translate those signals into ribcage movements that promote breathing. As a result, prey is immobilized and death ensues from asphyxiation. In the laboratory, these toxins are valuable tools for studies of nicotinic receptors.

Other toxins—from frogs, algae, or sea snails, for example—can also be used to study nicotinic receptors. Nicotine itself is a toxic substance and seems to have evolved as a natural insecticide.

Because of their wide distribution and critical physiological roles, nAChR are ideal targets for modification of brain and body functions. Not surprisingly, therefore, nicotinic receptors are targets for a variety of toxins and bioactive substances and are under intensive investigation to identify new medicines that can be used to treat neurological and/or psychiatric disorders as well as some diseases that strike outside the nervous system.

Team Members | Home

Barrow Neurological Institute of St. Joseph's Hospital and Medical Center, Phoenix, Arizona