Immediate and persisting effect of toluene chronic exposure on hippocampal cell loss in adolescent and adult rats

Abuse of toluene-containing volatile inhalants has become widespread among adolescents. Besides, because toluene is usually used as an industrial solvent in manufacturing of chemical pharmaceuticals and multiple commonly used household and commercial products, it has high potential for abuse for adults also. Long-term exposure to toluene vapor has a severe impact on the central nervous system, resulting in numerous neurological, neurobiological and behavioral impairments. Recently in the hippocampus some molecular and biochemical changes as a result of toluene chronic exposure were described. Such data point out the involvement of this area in the toluene addiction. However it remains uncertain whether toluene provokes structural alterations in the hippocampus. In this study we exposed male Wistar rats to 2000 ppm inhaled toluene for 40 days in rats at ages P 28–32 (adolescents) and P 70–75 (adults). The immediate and delayed effects of toluene chronic exposure (immediately after the end of toluene chronic inhalation and 90-day after the end of toluene chronic inhalation, correspondingly) on pyramidal cell loss in adolescent and adult rats was investigated. The results reveal that (i) chronic exposure to 2000 ppm of toluene chronic exposure alters the structure of hippocampus in adolescent and adult rats provoking both, immediate and delayed effects; (ii) the character of structural alterations depends upon the postnatal age of testing of the animals.

► Toluene chronic exposure provokes pyramidal cell loss in the hippocampus of adult and adolescent rats.
► Effect of toluene chronic exposure on hippocampal cell loss differs depending animal's age.
► In adolescent rats considerable cell loss is observed immediately after the end of toluene chronic exposure.
► In adolescent rat persistent effect does not differ significantly from immediate effect.
► In adult rats the persistent effect of toluene chronic exposure is significantly more substantial than immediate effect.