AimsAngiotensin(1-7) (Ang1-7) acting at the level of the rostral ventrolateral medulla (RVLM) affects arterial pressure. The cellular substrate of Ang1-7 remains unknown. We sought to determine which cell types in RVLM could mediate its actions and whether these are altered in the spontaneously hypertensive rat (SHR).Methods and resultsAstrocytes, catecholaminergic (CA-ergic) and non-CA-ergic neurones were targeted with adenoviral vectors in organotypic slice cultures from Wistar rats and SHR. Astrocytic Ca2+ signalling was monitored using a genetically engineered Ca2+ sensor Case12. CA-ergic neurones expressed enhanced green fluorescent protein (EGFP) under control of the PRS × 8 promoter, whereas non-CA-neurones expressed EGFP under control of the synapsin-1 promoter. Neurones were recorded in whole cell mode while [Ca2+]i was monitored using Rhod-2. RVLM astrocytes responded to Ang1-7 (200-1000 nM) with concentration-dependent [Ca 2+]i elevation. In SHR, the response to 1000 nM was significantly attenuated. The competitive Ang1-7 receptor antagonist A779, but not the AT1 receptor blocker (losartan), suppressed Ang1-7-induced [Ca2+]i elevations, which were also antagonized by blocking intracellular Ca 2+ stores. Ang1-7 evoked no consistent changes in [Ca2+]i or membrane excitability in CA-ergic or non-CA-ergic neurones in either rat strain.ConclusionAstroglia are a plausible cellular target of Ang1-7 in RVLM. Our data suggest that astrocytic responsiveness to Ang1-7 is reduced in SHR. We hypothesise that Ang1-7 modulates astrocytic signalling which in vivo may affect local metabolism and microcirculation, resulting in changes in activity of RVLM pre-sympathetic neurones and hence blood pressure.
- Ca sensor Case12
- Catecholaminergic neurones
- Non-catecholaminergic neurones
- Rostral ventrolateral medulla
- Spontaneously hypertensive rat