This study was designed to evaluate the responses of cardiovascular system to endothelin (ET) and neuropeptide Y (NPY) in 12 week-old SHR treated with or without enalapril (ENP) for 6 weeks. The diastolic blood pressure and heart rate were lower in EN...
This study was designed to evaluate the responses of cardiovascular system to endothelin (ET) and neuropeptide Y (NPY) in 12 week-old SHR treated with or without enalapril (ENP) for 6 weeks. The diastolic blood pressure and heart rate were lower in ENP-treated SHR than in control. The pressor response to intravenous, but not intracerebroventricular, ET or NPY was attenuated by ENP treatment. The chronotropic action induced by electrical stimulation was attenuated by ENP or ET. The negative chronotropic action of ET was blocked by yohimbine. The increase in aortic tension induced by electrical field stimulation (EFS) was depressed in ENP-treated group as compared with non-treated group, and enhanced by ET, but not NPY, in the non-treated group. The ET-induced increase in tension was enhanced by removal of endothelium in the control group but not in ENP-treated group. The plasma concentration of norepinephrine and ET-induced increase in concentration of norepinephrine and epinephrine in plasma were decreased in ENP-treated group. These results suggest that preventive effect of enalapril on the development of hypertension may result from depressing vasoactive action of endothelin and neuropeptide Y, and sympathetic neurotransmission at peripheral nervous system.