A method for direct measurement of afferent renal nerve activity in unanesthetized rats

This study introduces a novel method for recording afferent renal nerve activity (ARNA) in unanesthetized rats. A bipolar electrode was surgically implanted on the left renal nerve to record renal nerve activity (RNA), and efferent renal nerve activity (ERNA) was selectively blocked by administering 5% lidocaine via a polyurethane catheter placed over the renal artery-aorta junction. Lidocaine administration reduced RNA by approximately 82% relative to prelidocaine values, enabling the isolation of afferent nerve signals. Intrarenal arterial infusion of increasing doses of bradykinin (10, 20, 40, and 80 µg/kg) following lidocaine infusion produced a significant increase in ARNA, confirming preserved afferent function. This demonstrates the feasibility of this approach for investigating renorenal reflexes and the dynamic interplay between ARNA and ERNA, with implications for understanding homeostatic regulation and the pathophysiology of conditions such as hypertension and kidney disease.NEW & NOTEWORTHY This is the first method to enable real-time, selective measurement of ARNA in unanesthetized rats without interference from efferent signals. The use of targeted lidocaine administration allows functional separation of afferent and efferent components of renal nerve activity in vivo. This technique provides a tool to study renorenal reflexes under physiological and pathophysiological conditions, advancing our understanding of autonomic regulation in health and disease.