Effects of chronic toluene inhalation on avoidance conditioned behavior in rats.

Thirty-two Wistar albino rats were distributed at random in a factorial design 2 x 2, with two age groups (20 and 90 days old), and two treatments (chronically exposed to toluene vapors 30,000-40,000 ppm in air/15 minutes per day for 30 days, and controls with only air). Twenty-four hours after the last exposure, the rats were tested for conditioned behavior in a "T" maze of avoidance electric shock. Latency of initial response to escape (LIRE) and latency of escape (LE) were measured in seconds. Adult rats both exposed to chronic toluene inhalation and non-exposed showed higher values of LIRE and LE with respect young rats. Animals exposed to chronic toluene inhalation also presented higher values of latency in both LIRE and LE when compared to non-exposed to toluene (controls) of the same age. The differences were evaluated by Friedman's test. The findings are suggestive of brain dysfunction associated with chronic toluene inhalation, and may represent a delay to respond to a displeasure stimulus probably due to defect of internal mechanisms of facilitation-inhibition of neural impulses, mediated by neurotransmitters.