A COMPARISON OF THE ACUTE NEUROACTIVE EFFECTS OF DICHLOROMETHANE, 1,3-DICHLOROPROPANE, AND 1,2-DICHLOROBENZENE ON RAT FLASH EVOKED-POTENTIALS (FEPS)

Previous research showed that acute exposure to dichloromethane (DCM) produced a selective reduction in peak N-30 of flash evoked potentials (FEPs) in rats. In contrast, acute exposures to p-xylene or toluene s electively reduced FEP peak N-160. The present experiments compared th e effects of DCM (log P = 1.25; oil:water partition coefficient), 1,3- dichloropropane (DCP; log P = 2.00), and 1,2-dichlorobenzene (DCB; log P = 3.38) on FEPs recorded from adult Long-Evans rats, Before adminis tration of test compounds, FEPs were recorded for five daily sessions to develop FEP peak N-160. Test compounds were dissolved in corn oil a nd administered ip at doses based on proportions of their LD50 values. The doses were: DCM, 0, 57.5, 115, 230, or 460 mg/kg; DCP, 0, 86, 172 , 343, or 686 mg/kg; and DCB, 0, 53, 105, 210, or 420 mg/kg. Testing t imes after dosing varied among compounds and were based on pilot studi es to measure both the times of peak effect and recovery, Each solvent produced significant changes in the latency and amplitude of multiple components of the FEP waveforms. However, the predominant effect of D CM was to reduce the amplitude of peak N-30 (ED50 = 326.3 mg/kg), that of DCP was to reduce both peaks N-30 (ED50 = 231.0 mg/kg) and N-160 ( ED50 = 136.8 mg/kg), and that of DCB was to reduce peak N-160 (ED50 = 151.6 mg/kg). There was no consistent relationship between log P value s and the potency of the compounds to alter FEP peaks N-30 and N-160. The results suggest that organic solvents have multiple acute effects on the function of the central nervous system, which are not predictab le solely by the compound's lipid solubility. (C) 1997 Society of Toxi cology.