VESICAL-RENAL REFLEX - DIURESIS AND NATRIURESIS ACTIVATED BY INTRAVESICAL CAPSAICIN

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 know n about the sensory innervation of the bladder and renal function, so we studied the possibility of the existence of a vesical-renal reflex are. Twenty-one patients (9 men and 12 women) were randomised to recei ve intravesical infusion of saline solution containing 10 mu M capsaic in. Urine output, glomerular renal filtrate (GRF) and effective plasma renal flow (EPRF), measured by Technetium-99m diethylenetetramine-pen taacetic acid (DTPA) renal scintigraphy, were recorded over twenty min utes before and after the intravesical administration of capsaicin. Ur ine density, [Na+] and [K+] concentration, and prostaglandin E(2) excr etion were also determined before and after intravesical administratio n of capsaicin or vehicle. Instillation of saline solution containing 10 mu M capsaicin produced a significant increase of mean urine output , an increase of GRF, of EPRF and of [Na+] and [K+] urine concentratio n. An increase, not statistically significant, was observed of PgE(2) excrection. None of the patients treated with vehicle showed any modif ication of parameters examined. The present findings demonstrate a hit herto unrecognized effect: increased diuresis following selective chem ical stimulation of bladder efferents with capsaicin. The renal diuret ic response to intravesical capsaicin represents a working hypothesis about the possible involvement of a vesical-renal reflex are organized at spinal or supraspinal level.