Experiments were performed on male Sprague-Dawley (SD) rats anesthetized with a mixture of
urethane and
chloralose. A rat model of acute
myocardial ischemia (AMI) was made by
ligation of the left anterior descending branch of the coronary artery (LAD). After the LAD
ligation, the
ischemia area of the left ventricular wall became somewhat pale immediately. Under a light microscope, the pathological examination revealed that all the cells were swollen and in red color when the cardiac section was stained with
hematoxylin basic fuchsin picric acid (HBFP), which indicated a typical change in the
myocardial ischemia. In the AMI model, it was found that cardiac functions were markedly attenuated, such as decreases in the heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), maximal rate for left ventricular pressure rising and declining (+/-dp/dt(max)), velocity of contractile
element (V(CE)) and total area of cardiac force loop (L(0)), and an increase in the left ventricular end diastolic pressure (LVEDP). In such AMI rats, application of
electroacupuncture (EA) at "Neiguan"
acupoints (Pe 6) for 20 min could obviously improve the above-mentioned cardiac functions. After microinjection of nitro-
L-arginine (L-NNA), an inhibitor of
nitric oxide synthase (NOS), was made into the rostral ventrolateral medulla (RVLM), the curative effect of EA on
myocardial ischemia was reduced significantly or abolished, while after microinjection of
normal saline of the same volume was made into the RVLM, the improving effect of EA remained. These results suggest that the effect of EA on
myocardial ischemia is possibly mediated by the
nitric oxide (NO) in the RVLM.