Effect of toxin of Prymnesium patelliferum on neurotransmitter transport mechanisms: development of a sensitive test method

A crude extract of the ichthyotoxic phytoflagellate Prymnesium patelliferum strongly inhibited the uptake of neurotransmitters into isolated nerve endings (synaptosomes) and synaptic vesicles. These systems were about 100 and 10 times more sensitive toward the algal toxin, respectively, than a standard hemolysis assay often used for testing the toxicity of Prymnesium spp. and other ichthyotoxic algae. Prymnesium patelliferum grown in phsophorus-deficient (-P) medium was about five times more active than when grown in phosphorus sufficient (+P) medium. The inhibition ratio between the high-affinity synaptosomal uptake of L-glutamate and gamma-aminobyturic acid (GABA) was 1/2.7 for the -P culture and 1/1.9 for the +P culture. The inhibition ratios for the low-affinity vesicular uptake of L-glutamate, GABA, and dopamine (DA) were 1/5.8/0.3 and 1/1.7/0.2, respectively. The synaptosomal transport of L-glutamate is a rapid, simple, and sensitive test method for toxicity determination of Prymnesium spp. and will be a useful tool in the further isolation and purification of the toxic principles of this and other related algae. It is suggested that the toxin interferes with ion channels or acts as an ionopore.