In vivo and in vitro electrophysiological monitoring of rat neocortical activity after dietary fumonisin exposure.

Corn pellets, containing 30 mg/kg bw/day fumonisin B1 (FB1) or containing no FB1 were fed in two series of experiments to rats. Spontaneous and evoked potentials were measured in the neocortex both in vivo and in vitro in "corn fed control" rats and in rats after a five day dietary exposure to FB1. The FB1 content of corn was quantitated by HPLC. Auditory evoked potentials recorded in vivo on freely moving animals after feeding a corn diet containing FB1 for 5 days revealed a highly significant 20-60% decrease in the primary and mid-latency components; cortex slices in vitro showed a reduced excitability both in standard artificial cerebrospinal fluid (ACSF) solution and in a 4-aminopyridine induced epilepsy model. Spontaneous epileptic discharges after FB1 exposure had an increased latency, decreased frequency, longer duration and modified signal forms. Altered excitability and seizure susceptibility of the neocortex after fumonisin exposure are suspected to be associated with modified signal transmission. These changes may be due to concurrent effects of possible liver and renal toxicity or partly of nutritional deficiencies.