Marine Toxins Summary

Marine Toxins

Origin of Marine Shellfish Poisoning

  • Understand the origin of marine shellfish poisoning.

  • Understand the mechanism of ASP, PSP, NSP.

  • Gain insight into how this knowledge has informed research and understanding in Neuroscience.

Historical Incidents

  • 1961, Capitola CA: "Crazy" seabirds exhibited strange behavior; thousands died.

  • This incident inspired Hitchcock's movie "The Birds" (1963).

  • Prince Edward Island Incident (1987): Locals ate cultivated mussels, leading to deaths and serious illnesses with seizures.

  • Post-mortem examinations revealed massive damage to the hippocampus, amygdala, and entorhinal cortex.

  • Survivors experienced irreversible short-term memory deficits.

ASP Incident Details

  • November 22, 1987: Two individuals in Monckton, NB, showed gastroenteritis and confusion after eating mussels.

  • Similar cases emerged in Montreal; health officials traced the mussels to PEI.

  • Mice injected with mussel extracts died rapidly, exhibiting a characteristic "leg-scratch" behavior.

  • Symptoms included vomiting, diarrhea, confusion, memory loss, disorientation, seizures, and coma.

  • Post-mortem examinations revealed severe damage to the hippocampus and amygdaloid nucleus.

Domoic Acid

  • The culprit identified was domoic acid, leading to Amnesic Shellfish Poisoning (ASP).

  • Pure domoic acid given to monkeys caused similar symptoms to those observed in humans who consumed contaminated mussels.

  • 2.0−7.52.0-7.5 mg/kg injected in rats showed scratching, crab-like walking, praying, loss of balance, and seizures.

  • Lesions were found in the amygdala, cortex, hippocampus, hypothalamus, olfactory system, and retina.

  • Domoate is 2-3 times more potent than Kainate and 100 times more potent than glutamate in inducing epileptic seizures.

  • Produced by algal bloom of pseudonitzschia.

  • Taken up by seaweed.

  • Mussels eat seaweed.

Domoic Acid Mechanism

  • Acute neurotoxicity arising from its action on kainate receptors.

Saixitoxin

  • Causes Paralytic Shellfish Poisoning (PSP).

  • Found in mussels via alexandrium gymnodinium et al.

  • Blocks Na+Na+ channels, causing flaccid paralysis and death from respiratory failure.

  • Super-potent: 5 micrograms per Kg if LD50LD_{50} in man = fatal dose of 0.35 mg.

Brevetoxin

  • Causes Neurotoxic Shellfish Poisoning (NSP), a nonparalytic toxic syndrome.

  • Found in mussels via Karenia brevis.

  • Binds to the alpha subunit of VG Na+Na+ channels, causing persistent opening.

  • Symptoms: paresthesias, reversal of hot and cold temperature sensation, vertigo, and ataxia.

Uses of Marine Toxins

  • Potential as anesthetics (e.g., STX).

  • Kainic acid (from red alga Digenea simplexkainic) is used to make neurons oscillate in vitro.

Common Targets of Marine Toxins

  • Synthesized in dinoflagellates and accumulate in the food chain before affecting people.

Ciguatoxin

  • PCTX-1; effects at 80−100ngkg−180-100 ngkg^{-1}. A mystery toxin.

Brevetoxin Treatment Study

  • Injected epicortically in mice post-stroke to assess neural repair and functional recovery.