A neurophysiological method of rapid detection and analysis of marine algal toxins

We have examined the effectiveness of the in vitro rat hippocampal slice pr eparation as a means of rapidly and specifically detecting the marine algal toxins saxitoxin, brevetoxin, and domoic acid and have identified toxin-sp ecific electrophysiological signatures for each. Brevetoxin (PbTX3, 50-200 nM) produced a significant reduction in orthodromic population spike amplit ude which was quick to reverse during a 50 min wash-out, while antidromic p opulation spikes and field EPSPs exhibited only slight reductions, and fibr e spiof orthodrokes showed no change at all. Domoic acid (100 nM) produced a robust, reversible increase in amplitude mic spikes, and the appearance o f multiple spikes (i.e., epileptiform activity) within minutes of toxin was h-in. Other notable features of the domoic acid signature included a signif icant decrease in amplitude of the field EPSPs, and a complete absence of e ffect on either antidromic or fibre spikes. Fifty nanomolar saxitoxin (PSP) abolished all responses in all slices. Only antidromic spikes showed any r ecovery during wash-out. Field EPSP and fiber spike analysis further demons trated that the preparation is capable of reliably detecting saxitoxin in a linearly responsive fashion at toxin concentrations of 25-200 nM, and test s of naturally contaminated shellfish confirmed the utility of this assay a s a screening method for PSP. Our findings suggest that the in vitro hippoc ampal slice preparation has potential in the detection and analysis of thre e marine algal toxins important to the shellfish industry. (C) 1999 Elsevie r Science Ltd. All rights reserved.