Domoic acid is one of the best-known marine toxins, causative of important neurotoxic alterations. In the year 1987, domoic acid was responsible for four deaths and the illness of more than 100 people after consuming blue mussels (Mytilus edulis) harvested in the Cardigan Bay of Prince Edward Island, Canada. The symptomatology comprised three kinds of signs: gastrointestinal (nausea, vomiting,), cardiovascular (unstable blood pressure and arrhythmias), and neurological signs (disorientation, confusion, hallucinations, coma, and memory impairment). After this event was discovered the domoic acid epileptic. Nearly a year after the amnesic shellfish poisoning event, an 84 years old male survivor re-experienced severe seizures and was diagnosed with temporal lobe epilepsy caused by domoic acid intoxication. This toxin has a high affinity for the glutamate receptors (GluRs) subtypes: alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and KA receptors. The binding of domoic acid to receptors provokes an increase of calcium (Ca2+) levels, causing the release of Glu to the extracellular space, and the activation of N-methyl-d-aspartate (NMDA) receptors. The histological consequences of these cellular alterations comprise astrocytosis, cytoskeletal disarrangement and, finally, cell death.

Okadaic acid (OA) is a naturally occurring polyether toxin that was originally derived from marine dinoflagellates, Prorocentrium spp.. It is a reversible, potent and selective inhibitor of two serine threonine protein phosphatases: PP2A-C (PP2A) which is inhibited completely at 1 nM and PP1 which is inhibited at higher concentrations (IC50= 10-15 nM). PP2B is much less sensitive to okadaic acid than PP1, while PP2C is not inhibited. This selectivity is the basis for an improved identification and quantification procedure for these enzymes. The hydrophobic backbone of okadaic acid enables it to enter cells where it stimulates intracellular protein phosphorylation. It mimics the effects of insulin, enhances transmitter release at neuromuscular junctions, causes vasodilation and is a very potent tumor promoter. Okadaic acid is an extremely useful tool for studying cellular processes that are regulated by phosphorylation. Okadaic Acid is an activator of PKC.