Abstract
Behavioral toxicity of toluene has been measured in mice. Because of its small size the mouse can be confined in a 251. hermetically sealed chamber for several hours. Toluene was introduced through a port and vaporized by a hotplate. Samples of chamber air for analysis were taken through another port. A smaller mesh cage held the mouse within the larger chamber. Schedule-controlled responding was developed by arranging that a response, breaking a beam of light, was followed by milk under an FI 60-sec schedule. Responding was much more rapid in the presence of stimuli correlated with the FI schedule than when the schedule was not operating. Standard sessions consisted of alternating series of 8 consecutive FI 60-sec and interseries 30-min time-outs.
Following introduction of liquid toluene, the concentration in the chamber reached its asymptote within 60 sec. Toluene disappeared from the atmosphere of the unopened empty chamber at the rate of 0.2%/hr. When the mouse cage was in the chamber the disappearance was 1.5%/hr and when a mouse was also present it was 3.5%/hr. Effects of toluene on the behavior of the mouse reached a plateau within 30 min of continued exposure to a fixed concentration. Concentration-effect curves were constructed from the number of responses in a series of FI's following 30-min exposure to a concentration of toluene as compared to the control number on that day. In some experiments mice were exposed to a single concentration of toluene: in other experiments, more toluene was added after a series of FI so the mice were exposed to incrementally increasing concentrations. The two procedures generated similar concentration-effect curves. Toluene increased the rate of responding in most mice at levels of about 700 ppm. Higher concentrations progressively reduced responding. The ED 50 (the concentration reducing responding by 50%) averaged 1657 ppm in 10 mice.