Neosaxitoxin

Neosaxitoxin (NSTX) is a naturally occurring neurotoxin that is produced by certain species of marine dinoflagellates (algae) and cyanobacteria. It is one of the many saxitoxin analogs responsible for paralytic shellfish poisoning (PSP).

Structure and Mechanism

Neosaxitoxin is a tricyclic compound that is structurally similar to saxitoxin. It has two guanidinium groups that are critical for its activity. NSTX blocks voltage-gated sodium channels on the nerve cell membrane, preventing the propagation of action potentials and leading to paralysis.

Sources

NSTX is produced by certain species of marine dinoflagellates (such as Alexandrium tamarense and Gymnodinium catenatum) and cyanobacteria (such as Anabaena circinalis and Aphanizomenon flos-aquae). These organisms are often involved in harmful algal blooms (HABs), which can lead to PSP in humans if contaminated shellfish are consumed.

Toxicity

The toxicity of NSTX is similar to that of saxitoxin. It is highly potent, with a lethal dose in mice of approximately 5.3 μg/kg when administered intravenously. Symptoms of PSP include numbness, tingling, nausea, and in severe cases, paralysis and respiratory failure.

Medical Uses

NSTX has potential medical applications due to its ability to block nerve conduction. It has been investigated for use as a long-acting local anesthetic, and in the treatment of chronic pain.

See Also

• Saxitoxin
• Paralytic shellfish poisoning
• Harmful algal bloom
• Voltage-gated sodium channel

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