Cardiovascular and renal responses produced by central orphanin FQ/nociceptin occur independent of renal nerves

The present study investigated the role of the renal nerves in mediating th e cardiovascular and renal responses produced by the central administration of the opioid-like peptide orphanin FQ/nociceptin (OFQ/N) in conscious Spr ague-Dawley rats. In conscious rats, OFQ/N (10 mu g icy) produced a transie nt bradycardia and hypotension (nadir 20 min). Although renal sympathetic n erve activity (RSNA) initially remained unchanged, a delayed renal sympatho inhibitory response occurred after recovery (30 min) of blood pressure. By 30 and 70 min postinjection, RSNA decreased to 75 and 66% of control, respe ctively. Coinciding with the decrease in RSNA, central OFQ/N elicited a diu resis and antinatriuresis that occurred independent of changes in renal hem odynamics. In other studies, intracerebroventricular OFQ/N produced similar cardiovascular and renal excretory responses in bilaterally renal-denervat ed rats. Finally, in conscious sinoaortic deafferentiated rats, intracerebr oventricular OFQ/N produced a rapid decrease in RSNA (55% of control, 10 mi n; 38% of control, 20 min) that paralleled the onset of the hypotension and bradycardia. These studies demonstrate that in conscious rats, intracerebr oventricular 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 r ats, the cardiovascular and renal excretory responses produced by central O FQ/N occur by a pathway that is independent of intact renal nerves or chang es in renal hemodynamics.