Vesical-Renal Reflex: Diuresis and Natriuresis Activated by Intravesical Capsaicin

Abstract

In the last years the role of capsaicin sensitive innervation, in the activation of the micturition reflex, has been reported in many papers. In our experience, upon the intravesical administration of capsaicin in humans, we noticed an increase of diuresis. No interaction is known about the sensory innervation of the bladder and renal function, so we studied the possibility of the existence of a vesical-renal reflex arc. Twenty-one patients (9 men and 12 women) were randomised to receive intravesical infusion of saline solution containing 10 μM capsaicin. Urine output, glomerular renal filtrate (GRF) and effective plasma renal flow (EPRF), measured by Technetium-99m diethylenetetramine-pentaacetic acid (DTPA) renal scintigraphy, were recorded over twenty minutes before and after the intravesical administration of capsaicin. Urine density, [Na⁺] and [K⁺] concentration, and prostaglandin E₂ excretion were also determined before and after intravesical administration of capsaicin or vehicle. Instillation of saline solution containing 10 μM capsaicin produced a significant increase of mean urine output, an increase of GRF, of EPRF and of [Na⁺] and [K⁺] urine concentration. An increase, not statistically significant, was observed of PgE₂ excrection. None of the patients treated with vehicle showed any modification of parameters examined. The present findings demonstrate a hitherto unrecognized effect: increased diuresis following selective chemical stimulation of bladder efferents with capsaicin. The renal diuretic response to intravesical capsaicin represents a working hypothesis about the possible involvement of a vesical-renal reflex arc organized at spinal or supraspinal level.

Keywords:

• vesical-renal reflex
• intravesical capsaicin
• diuresis and natriuresis