The present study investigated the role of the renal nerves in mediating the cardiovascular and renal responses produced by the central administration of the opioid-like peptide orphanin FQ/nociceptin (OFQ/N) in conscious Sprague-Dawley rats. In conscious rats, OFQ/N (10 microgram icv) produced a transient bradycardia and hypotension (nadir 20 min). Although renal sympathetic nerve activity (RSNA) initially remained unchanged, a delayed renal sympathoinhibitory response occurred after recovery (30 min) of blood pressure. By 30 and 70 min postinjection, RSNA decreased to 75 and 66% of control, respectively. Coinciding with the decrease in RSNA, central OFQ/N elicited a diuresis and antinatriuresis that occurred independent of changes in renal hemodynamics. In other studies, intracerebroventricular OFQ/N produced similar cardiovascular and renal excretory responses in bilaterally renal-denervated rats. Finally, in conscious sinoaortic deafferentiated rats, intracerebroventricular OFQ/N produced a rapid decrease in RSNA (55% of control, 10 min; 38% of control, 20 min) that paralleled the onset of the hypotension and bradycardia. These studies demonstrate that in conscious rats, intracerebroventricular OFQ/N produces a centrally mediated inhibition of RSNA which, due to activation of baroreflex mechanisms, is temporally dissociated from the hypotensive and bradycardia responses. As revealed in renal-denervated rats, the cardiovascular and renal excretory responses produced by central OFQ/N occur by a pathway that is independent of intact renal nerves or changes in renal hemodynamics.