Multimodal effects of acute exposure to toluene evidenced by sensory-evoked potentials from Fischer-344 rats.
Male Fischer-344 rats were exposed by inhalation to 500, 2000, 5000, 8000 and 16000 ppm toluene for 30 min in two experiments. Exposures up to 8000 ppm in Experiment 1 caused concentration-related changes in the click-elicited brainstem auditory-evoked response (CBAER), flash-evoked potential (FEP) and somatosensory-evoked potential (SEP). Latencies of CBAER components were prolonged and amplitudes of late components were increased by toluene. Toluene did not detectably alter the latencies of FEP or SEP components. Early FEP component-amplitudes were increased and late component-amplitudes were decreased; toluene also induced a poststimulus oscillation in the FEP. Most component-amplitudes of the SEP were substantially increased, but N2P2 amplitude appeared to be more sensitive than other components to depressant effects of the solvent. The same effects on the CBAER were observed in Experiment 2, but a more substantial increase in the amplitudes of late components elicited by tone pips suggested that frequency-dependent cochlear irritation might underlie previously observed subchronic ototoxicity. These effects were increased by exposure to 16000 ppm toluene. Effects like those observed in Experiment 1 were noted on the FEP, but the oscillations were less with exposure to 16000 than 8000 ppm. Changes in the SEP were evident within 2 minutes of exposure onset, and amplitudes increased over the course of about 15 min, leveling off or decreasing thereafter. The amplitude of the N2P2 component was again less influenced than other components during exposure to 8000 ppm and was reduced to less than baseline amplitude by 16000 ppm. Effects of concentration and rates of development and recovery were systematically related to SEP component latency. Toluene appears to have both enhancing and inhibiting effects on neural pathways serving sensory systems, depending on the modality and the site of generation of the components within modalities. A particular balance between these properties might relate to the hedonic characteristics of this abused solvent.
Rebert
C S
CS
SRI International, Menlo Park, CA 94025.
Matteucci
M J
MJ
Pryor
G T
GT
D000161:Acoustic Stimulation; D000818:Animals; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D011930:Reaction Time; D014050:Toluene / Q000494:pharmacology*
D014050:Toluene