Nicotine-depressed function in isolated rat heart

Experiments were conducted to assess the effects of nicotine on the isolated rat heart. Hearts removed from laboratory rats were perfused via the aorta with oxygenated (95% O2-5% CO2) Krebs-Henseleit solution. After 30 min, the hearts were challenged with perfusate containing nicotine. Heart rate and coronary flow decreased in response to nicotine concentrations of 5 micrograms/ml or above. Solutions containing 5, 10 and 20 micrograms/ml nicotine depressed heart rate by 9, 29 and 25%, and coronary flow by 11, 28 and 33%. Pulse pressure was significantly depressed by 20 micrograms/ml nicotine. Perfusion with nicotine-free solution for 10 min completely reversed the decreases in heart rate, coronary flow and pulse pressure. These results indicate that nicotine continuously infused into the isolated rat heart depresses heart rate and coronary flow in a dose-response manner and that these changes are reversible over the range of concentrations used.