Effect of lisinopril on tissue levels of neuropeptide Y in normotensive and spontaneously hypertensive rats

Angiotensin-converting enzyme (ACE) inhibitors reduce systemic and coronary vasoconstriction by modulating sympathetic neuroeffector function and by d ecreasing sympathetic activation. Here, blood pressure, and tissue concentr ations of noradrenaline and neuropeptide Y (NPY) were studied in normotensi ve and spontaneously hypertensive rats (SHR) after 2 weeks treatment with l isinopril (0.3 mg/day; osmotic mini-pump). MAP was reduced in both normoten sive rats and SHR after lisinopril by 32 mm Hg and 66 mm Hg respectively (P < 0.001 compared to corresponding control rats). NPY levels were significa ntly higher in extracts of atria, kidney, spleen and adrenal of normotensiv e rats compared to SHR. Lisinopril treatment increased NPY levels in atria and skeletal muscle extracts of SHR by 15% and 70% respectively (P < 0.05). Lisinopril also significantly increased noradrenaline content of the atria by 16% in SHR (P < 0.05). The decrease in MAP and increase in tissue level s of sympathetic neurotransmitters provide further evidence that inhibition of ACE decreases sympathetic neurotransmission leading to accumulation of stored neurotransmitters.