Experimental estimation of addictive potential of a mixture of organic solvents.

In the present study we investigated in rats the reinforcing properties of glue vapours which are a mixture of four organic solvents (toluene 25%, benzine fraction 37%, ethyl acetate 31% and methylene chloride 7%). This mixture is used as a glue thinner and is a very popular among glue-sniffing children. Immediately after inhalation at a concentration of 7200 ppm, the glue vapours increased locomotor activity in the open field and response rate of self-stimulation in the lateral hypothalamus. Contrary to classical drug abuse, glue vapours enhanced the threshold current of self-stimulation. While the response rate of self-stimulation decreased to the control level 30 min after inhalation, the threshold current was still enhanced. Increasing the concentration of the vapours produced a decrease in response rate of self-stimulation and locomotor activity. When glue vapours were inhaled at a concentration of 14,400 ppm and higher, the response rate of self-stimulation was completely suppressed. The discriminative stimulus effects of the glue vapours appeared to be similar to those of general anaesthetics such as ether and pentobarbital. At vapour concentrations of 7200 and 14,400 ppm, conditioned place preference was established. The ability of solvents to reinforce conditioning in the place preference paradigm and to activate the brain reward system in intracranial self-stimulation experiments may be useful for predicting the addictive potential of inhalants.