Altered atrial responses to drugs after acute exposure to nitrogen dioxide and/or ethanol

The responses of atria isolated from four groups of rats: (a) control (air/H2O) and test animals treated with (b) 5 PPM nitrogen dioxide NO2 for 72 hours, (NO2/H2O), (c) 10% ethanol (ET) in water for 13 days, (air/ET), or (d) combination of NO2 and ET (NO2/ET). Isolated atria were tested with norepinephrine and dose response curves determined. The chronotropic responses among groups were not different. However, there were significant differences when tested with pilocarpine and to lesser extent to increased calcium concentration in the bathing medium. Ethanol and/or NO2 attenuates parasympathetic activity possibly by altering receptor numbers or activity. The changes in calcium activity may result from altered calcium channel activity. This data indicates that acute exposure to NO2, ET and/or the interaction between these agents can alter cardiac activity.