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

This study introduces a novel method for recording afferent renal nerve activity (ARNA) in unanaesthetised 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 pre-lidocaine 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 reno-renal 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.