Short- and long-term effects of chronic toluene exposure on recognition memory in adolescent and adult male Wistar rats.

Abuse of toluene-containing volatile inhalants, particularly among youth, is of significant medical and social concern worldwide. Teenagers constitute the most abundant users of toluene and the majority of adult abusers of toluene started as teenagers. Although the euphoric and neurotoxic effects of acute toluene have been widely studied, lasting effects of chronic toluene exposure, especially in various age groups, have not been well investigated. In this study, we used adolescent and adult male Wistar rats to evaluate the short- and long-term effects of chronic toluene on various behaviors including cognitive function. Daily exposure to toluene (2000 ppm) for 40 days (5 min/day) resulted in age-dependent behavioral impairments. Specifically, adolescent animals showed recognition memory impairment the day after the last exposure, which had normalized by day 90 post- exposure, whereas such impairment in adult animals was still evident at day 90 post-exposure. Our data suggest that age-dependent responses should be taken into consideration in interventional attempts to overcome specific detrimental consequences of chronic toluene exposure.

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.