Parasympathetic nerves in the kidney pelvis contribute to blood pressure regulation

The existence of parasympathetic innervation in the kidney has long been controversial. Recent anatomical studies have provided evidence supporting such innervation by demonstrating the presence of acetylcholine (ACh) metabolic enzymes and tracing a brain-kidney vagal axis. Although these findings confirm the anatomical pathway, the functional capacity of these nerves to release neurotransmitters remains unverified, and the physiological role of this pathway is still unknown. We delineated the innervation of the renal pelvis by co-labeling sympathetic, parasympathetic, and sensory nerves. ACh receptors expression was assessed through single-cell RNA sequencin, quantitative reverse transcription polymerase chain reaction, and fluorescent in situ hybridization. The ACh release from the renal nerves was monitored via fiber photometry with a genetically encoded ACh sensor. Optogenetic activation was employed to investigate the functional effects of renal parasympathetic efferent and afferent pathways on blood pressure and heart rate. We identified multi-component innervation in the renal pelvis, including sympathetic, parasympathetic, and sensory nerves. Moreover, muscarinic ACh receptors were found to be expressed in this region. Neurogenic ACh release from renal nerves was also detected following transmural stimulation. Furthermore, optogenetic activation of the vagal brain–kidney afferent pathway resulted in a decrease in blood pressure. These results suggest that the renal pelvis receives dual autonomic innervation from both sympathetic and parasympathetic nerves, and the vagal renal afferents are involved in blood pressure regulation. Overall design: Renal pelvises were dissected from 15 adult (10-week-old) male C57BL/6 mice under a surgical microscope. The tissues were then digested into single-cell suspensions and subsequently analyzed by single-cell RNA sequencing.