Evoked potential and EEG study of the neurotoxicity of hydramethylnon in rats

The objective of the study was to assess the neurotoxicity, using electrodiagnostic tests, of hydramethylnon (Amdro, AC 217,300), an insecticide marketed for the treatment of red imported fire ants, cockroaches, and other insects. Animals were male Fisher 344 albino rats and Long-Evans hooded rats. Brainstem auditory, visual, and somatosensory evoked potentials (BAER, VEP, SEP) and electroencephalograms (EEG) were recorded from implanted screw electrodes before and at multiple time points through day 10 after a single oral dose of hydramethylnon (at 50% or 75% of the LD₅₀) plus vehicle, or vehicle alone. No evidence of nervous system toxicity was detected with either BAER, VEP, or SEP recordings. Spectral analysis of EEGs recorded over 7days demonstrated a time-limited increase in power at low frequencies and decrease at high frequencies, reflecting a sedative effect. A dose-dependent weight loss was observed. Single-exposure poisonings with AC 217,300 can be expected to produce anorexia and CNS depression, but not lethality.