[Sex difference in operant behavior following single exposure to carbon monoxide in adult rats]

Sex difference of effects of single exposure of carbon monoxide (CO) on operant behavior was studied in adult rats. The animals were obtained by continued selective breeding and have a high level of avoidance ability and small individual differences (THA rat: Tokai high avoider rat). Experiments were conducted as follows: Exposure were carried out at the concentrations of 50, 100, 200 and 400 ppm of CO gas for 4 h in THA rats, and their operant behavior was studied by Sidman avoidance test conducted 1 h before and after CO exposure. Rats whose carboxyhemoglobin (COHb) in blood was determined after the termination of CO exposure were of the same strain and age as those that underwent operant behavior test. Exposure of CO 50 ppm did not produce any marked change in operant behavior. In male rat groups, response counts in the Sidman avoidance test decreased after exposure to CO 100, 200 and 400 ppm when compared to the value before exposure, but increase in shock counts was observed only by exposure to CO 400 ppm. In female rat groups, response counts decreased after the exposure to CO 200 and 400 ppm, but shock counts did not show any marked change at all the CO exposure concentrations. COHb concentrations immediately after the exposure to CO 50, 100, 200 and 400 ppm for 4 h were 9.1 +/- 1.2, 13.5 +/- 0.5, 24.3 +/- 0.7 and 43.6 +/- 1.6%, respectively, in males, and 9.2 +/- 1.1, 13.7 +/- +/- 0.8, 24.0 +/- 1.0 and 42.0 +/- 1.4%, respectively, in females.(ABSTRACT TRUNCATED AT 250 WORDS)