NEURONAL LOSS IN HIPPOCAMPUS IN RATS EXPOSED TO TOLUENE

Both clinical and epidemiological studies of the effects of exposure t o toluene have shown that long-term exposure may result in chronic tox ic encephalopathy, where one of the major symptoms is memory deficits. We have attempted to identify the structural basis of the toxic effec ts of toluene in the hippocampus, a region of the brain known to be in volved in learning and memory processes and well suited for stereologi cal analysis. Rats were exposed to 1 500 ppm of toluene, six hours per day, five days per week for six months. This was followed by a tb ur- mon th-period without exposure prior to sacrifice. The total number of neurons in each of the five subdivisions of hippocampus of six expose d and six control rats was estimated with the optical fractionator. A statistically significant neuron loss of 16% was found in regio inferi or (CA3 and CA2) of the exposed rats. (C) 1996 Intox Press, Inc.