Temporal changes in repeated acquisition behavior after carbon monoxide exposure

Behavioral effects of carbon monoxide (CO) were studied in rats following 90-min exposures to concentrations ranging from 500 to 1200 parts-per-million (ppm). The animals performed on a repeated acquisition of behavioral chains procedure in which food reinforcement depended on the correct completion of a four member response sequence on three separate response levers. The sequence of correct lever presses changed daily. Periodically, the animals were individually exposed to either air or a CO concentration of 500, 850, or 1200 ppm for 90 min prior to a behavioral session that terminated after the completion of 150 sequences. Carboxyhemoglobin measurements indicated equilibration after 60 minutes of exposure. Concentrations of 850 and 1200 ppm produced increased pausing between responses throughout the test sessions. The increased time required to complete sequences occurred primarily during the first component of the response sequence. Accuracy of responding as measured by total error and timeout responses was not affected by CO exposure.