Overexpression of OX1R in the PVN Induced Sympathoexcitation and Elevated Blood Pressure in Male Sprague Dawley Rats

Introduction: The hyperactivity of the orexin system has been implicated in the pathogenesis of various diseases, including hypertension. However, its role in chronic high blood pressure development remains unclear. Hypothesis: We hypothesized that chronic overexpression of orexin receptor type 1 (OX1R) in the paraventricular nucleus (PVN) induces sympathoexcitation, and lead to elevated blood pressure. Methods: To test this hypothesis, we bilaterally injected AAV2-OX1R into the PVN of male Sprague Dawley (SD) rats, while AAV2-GFP-injected rats served as controls. The rats' blood pressure and heart rate were monitored using a radio telemetry transducer system. Results: AAV2-OX1R-treated rats exhibited mild, but significantly elevated systolic, diastolic, and mean arterial pressure (MAP) compared to controls, starting two weeks post-injection and peaking at three weeks (MAP: Control: 99.5±0.9 mmHg vs. AAV2-OX1R: 107.9±1.2 mmHg, n=7~9 per group). These increases persisted until the eighth week when the rats were euthanized. However, the heart rate remained unchanged between groups. To further investigate the functional impact of OX1R overexpression, we compared blood pressure and renal sympathetic nerve activity (RSNA) responses to bilateral PVN administration of orexin A (OXA). OXA significantly increased MAP (Control: +16.3 mmHg, n=6, vs. AAV2-OX1R: +26.59 mmHg, n=8, p<0.01) and RSNA (Control: +72.74%, n=6, vs. AAV2-OX1R: +155.40%, n=8, p<0.05) in OX1R-overexpressing rats compared to controls. To assess whether oxidative stress contributes to OX1R-mediated blood pressure increase and sympathoexcitation, we intracerebroventricularly administered Mitoprobe, a probe that binds reactive oxygen species (ROS) and triggers fluorescence, into the rats. Confocal imaging revealed a significant increase in ROS fluorescence intensity in the PVN of AAV2-OX1R-treated rats (1.3-fold, p<0.05), along with a marked elevation in the percentage of ROS fluorescence area in AAV-OX1R-infected cells compared with control AAV-GFP infected cells (Control: 0.70% vs. AAV-OX1R:10.35%, p<0.0001). Conclusion: These findings suggest that chronic OX1R overexpression in the PVN increases blood pressure and sympathetic outflow, which may be partly due to excessive ROS production. This work was supported by NIH grants R01HL163159 (Shan), R15HL150703 (Shan), and R15EB035866 (Bi). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.