gms | German Medical Science

Recent results of sympathetic nerve recordings in patients with renal insufficiency suggest a role of renal afferent nerves in upregulated sympathetic nerve activity and hypertension. It is unknown if renal afferent nerves are stimulated mechanically or chemically. Hence, we tested the hypothesis, that sensoric nerves with renal afferent axons in hypertensive models of rats have an altered sensitivity to mechanical stimuli as compared to controls. Neurones with renal afferents from dorsal root ganglions of several hypertensive rat models were cultured on coverslips (rats pretreated with intrarenal phenol, 2 kidney-1clip hypertensive and 5/6 nephrectomized rats, spontaneously hypertensive rats, respective controls). Whole cell patch recordings were obtained from the cells and current-time relationships established. Cells of all groups were characterised under control conditions and after exposure to hypoosmotic mannitol solution to induce mechanical stress. Cells with axons from renal and non-renal sites were investigated. Cells with renal axons were labelled with a specific dye. In hypertensive rats pretreated with intrarenal phenol, responses of cells with renal axons were significantly different from normotensive controls: (phenol pretreated: control - 226±60 pA; hypoos. -395±95 pA vers normotensive: control - 198±30 pA; hypos. -604±90* pA ; * p<0,05 vers. control). In contrast, in all other models the responses of neurons with renal axons to mechanical stress were similar to their normotensive controls.

In conclusion, sensoric dorsal root ganglion cells with renal afferents exhibited impaired responses to mechanical stimuli in rats pretreated with intrarenal phenol application but not in other models of secondary or genetic hypertension. Hence, renal afferents might be specifically involved in the upregulation of sympathetic nerve activity in hypertension after limited intrarenal injury to phenol.