AT1a Receptor Upregulation in the MnPO Following CIH Leads to Sustained Hypertension

Abstract

Angiotensin type 1 (AT1) receptors play a central role in many forms of neurogenic hypertension. Two distinct subtypes, At1a and AT1b, exist for AT1 receptors. Activation of the AT1a subtype is characterized by increased sympathetic nerve activity and hypertension. The Median Preoptic Nucleus (MnPO) expresses both subtypes of the angiotensin receptor and our lab has previously demonstrated that AT1a message is increased in MnPO brain punches following CIH. This study sought to determine if changes in expression of the angiotensin receptor subtypes play a role in the sustained hypertension that develops from chronic intermittent hypoxia (CIH). We hypothesized that AT1a receptor expression increased and AT1b receptor expression remained unchanged resulting in the sustained elevation in blood pressure from CIH. Rats were microinjected in MnPO with an adeno‐associated virus loaded with a shRNA construct to prevent AT1a expression (shAT1a) or a scramble construct (shSCR). After recovery, rats were exposed to a 7 day CIH or normoxic protocol. Laser Capture Microdissection and qRTPCR was performed to determine the receptor subtype expression in MnPO with ribosomal subunit S18 as the control. shSCR rats exposed to CIH had significantly more AT1a RNA than their normoxic counterparts (P<.05), but their expression of AT1b remained constant. shAT1a CIH rats did not exhibit the sustained component of hypertension found in shSCR CIH animals and their MnPO AT1a message was reduced compared to control. Overall this indicates that the pathophysiological blood pressure increase during CIH is in part mediated by increases in AT1a receptor subtype expression in the MnPO.