Interaction of central mu opioid and nociceptin systems in the regulation of renal excretory function

Intracerebroventricular (i.c.v.) injection of the mu-opioid agonist, dermorphin (DER), or the endogenous opioid-like peptide nociceptin (NOC) produces a water diuresis in conscious rats. To examine how these systems may interact, we examined the renal responses produced by concurrent activation of central muopioid and NOC systems. Sprague-Dawley rats were instrumented with arterial and venous catheters and a bladder cannula for collection of urine. During continuous i.v. infusion of isotonic saline (55 μl/min), changes in urine flow rate (V) and urinary sodium excretion were measured during control (C, 20 min) and for 70 min (10 min consecutive periods, t10-t70) starting immediately after i.c.v. injection of DER (0.33 nmol/kg, n=5), NOC (10 μg total, n=6), or DER followed by NOC (same doses, n=7). Results: Values are means ± S.E. for V data collected during C and indicated time points after i.c.v. drug injection.*p