Angiotensin‐(1–7) increases neuronal potassium current via a nitric oxide‐dependent mechanism

Angiotensin 1–7 [Ang‐(1–7)] signaling in the brain may play an important protective role in cardiovascular diseases by decreasing sympathetic output. It is generally well‐accepted that nitric oxide (NO • ) in the brain functions as a sympatho‐inhibitory molecule. We hypothesized that Ang‐(1–7) increases NO • in neurons and modulates neuronal activity. We tested this hypothesis in catecholaminergic CATH.a neurons. Protein analysis revealed these neurons express the Ang‐(1–7) receptor (MasR) and three isoforms of NO • synthase (nNOS, eNOS, iNOS). Expression of MasR, nNOS, and eNOS protein markedly increased in CATH.a neurons following six days of differentiation with N 6 ,2′‐ O ‐Dibutyryladenosine 3′,5′‐cyclic monophosphate sodium salt (dbcAMP, 1 mM). As measured by DAF‐FM fluorescence and confocal microscopy, Ang‐(1–7) (100 nM) increased NO • levels in differentiated CATH.a neurons (31 ± 3%; P<0.05 vs. baseline) and this response was attenuated (P<0.05) by the MasR antagonist A779 (5 ± 3%), non‐specific NOS inhibitor (L‐NAME; −5 ± 1%), and nNOS inhibitor (SMTC; −5 ± 7%). Using the whole‐cell patch‐clamp technique, we observed that Ang‐(1–7) increased outward K + current (I Kv ) in differentiated CATH.a neurons (53 ± 6% increase; P<0.05 vs. vehicle). These findings indicate that Ang‐(1–7) increases nNOS‐dependent NO • levels via MasR activation and elevates I Kv in differentiated CATH.a neurons. NIH P01HL062222