Cardiovascular and renal effects of nociceptin/orphanin FQ: a new mediator to target?

Nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ peptide receptor. N/OFQ acts directly on blood vessels as a relaxant, and is unlikely to cross the blood-brain barrier due to its size. In anesthetized rats and conscious animals, intravenous N/OFQ produces transient hypotension and bradycardia that may involve interactions with the sympathetic and parasympathetic nervous systems. Injected intracerebro-ventricularly or directly into brain tissue, N/OFQ also affects the cardiovascular system. For example, N/OFQ causes water diuresis (aquaresis), which may represent the most immediate potential of targeting N/OFQ in the cardiovascular/ renal systems. Aquaretics are useful in the treatment of edema/hyponatremia which ultimately occurs in end-stage heart failure, liver cirrhosis and the syndrome of inappropriate secretion of antidiuretic hormone.