Nociceptin receptor

An additional opioid receptor has been identified and cloned based on homology with the cDNA. This receptor is known as the nociceptin receptor or ORL 1 receptor. Its natural ligand is known alternately as nociceptin or orphanin FQ.

Mechanism
Nociceptin is thought to be an endogenous antagonist of dopamine transport that may act either directly on dopamine or by inhibiting GABA to affect dopamine levels. Within the central nervous system its action can be either similar or opposite to those of opioids depending on their location. It controls a wide range of biological functions ranging from nociception to food intake, from memory processes to cardiovascular and renal functions, from spontaneous locomotor activity to gastrointestinal motility, from anxiety to the control of neurotransmitter release at peripheral and central sites.

Applications
ORL 1 agonists are being studied as treatments for heart failure and migraine while nociceptin antagonists may have antidepressant qualities.

The novel drug buprenorphine is a partial agonist at ORL 1 receptors while its metabolite norbuprenorphine is a full agonist at these receptors.