The effect of chronic exposure to 100 ppm carbon monoxide on brain biomines, serum corticosterone and organ weights in rats.

The effect of chronic exposure to 100 ppm (0.01%) CO on pituitary-adrenal activity was evaluated by measuring serum corticosterone and brain bioamine levels in the rat. Exposure to CO for 1 month induced a decrease in the brain serotonin levels. Serum corticosterone, brain dopamine and noradrenaline as well as the weight of the adrenal glands, lungs, spleen and liver were unchanged. After two months of exposure, serum corticosterone and brain serotonin levels were elevated and the liver weight was significantly lower. This suggests that at this chronic low concentration CO acts as a stressor, and the organism initiates a general defensive reaction. The effect of CO on the pituitary-adrenal axis could be mediated by a central neuronal pathway.