Esfenvalerate belongs to the pyrethroid group of insecticides which display significant selective
toxicity against insects compared to mammalian species, nevertheless, they may pose health risks,
especially in case of accidental exposure. The aim of the present study was to model the effect of
acute, relatively high-dose exposure of the esfenvalerate-containing formulation Sumi-Alpha®.
Eventual functional alterations in the central nervous system and in the gastrointestinal tract
were studied on in vitro tissue preparations at different delays after intragastric administration to
rats. Neuronal effects were characterized by field potential recording in cortical and hippocampal
brain slices, while gastrointestinal effects were examined by analyzing the motility and excitability
of isolated ileum segments. On the brain slices originating from esfenvalerate-treated animals,
changes in excitability of both inhibitory and excitatory type could be observed. Voltage thresholds
necessary to evoke responses in neocortex slices were elevated, and population spike amplitudes
were lower in hippocampal slices. However, epileptiform potentials with pronounced late
components were also observed. A decreased long-term potentiation (LTP) could be seen in both
brain areas after esfenvalerate treatment. Seizure susceptibility of the slices was not significantly
altered, but tended to be somewhat higher in slices originating from treated rats. In ileum segments,
both spontaneous and acetyl-choline (ACh)-elicited contractions were modified by treatment.
Esfenvalerate raised the amplitude of contractions in the low ACh concentration range.
However, the solvent xylene also considerably contributed to the detected changes. We can conclude
that a relatively high, single oral dose of Sumi-Alpha® exerted mild and temporary effects on
the elementary brain functions and intestine functions of the rat
