The effects of brief exposures to carbon monoxide on temporally differentiated responding

Four rats were trained on a differential-reinforcement-of-low-rate schedule under which only responses separated by intervals of 21 seconds produced food. Ninety-minute exposures to 100, 250, 500, 600, 750, and 1000 ppm carbon monoxide were given. Overall response rates were lower than rates in control sessions for all subjects at 750 ppm and higher concentrations. Measures of temporal discrimination (distributions of interresponse times), however, were not disrupted. The primary effect of the higher concentrations of carbon monoxide was to produce extended pausing or complete cessation of responding at some point in the session. Until pausing occurred, however, the control rate and patterning of responding obtained. The results are consistent with the growing body of evidence that carbon monoxide has a general rate-decreasing effect but no specific effect on measures of temporal discrimination.