Opioid receptor-like 1 (ORL-1) (ORL-1)

The Opioid receptor-like 1 (ORL-1), also known as the Nociceptin receptor (NOP), is a G protein-coupled receptor (GPCR) belonging to the opioid receptor family [1, 2]. Discovered in 1994, it shares high structural homology with classical opioid receptors (mu, delta, and kappa) but does not bind traditional opioid ligands with high affinity [4, 6]. Instead, it is specifically activated by the endogenous neuropeptide nociceptin, also known as orphanin FQ [2, 3]. ORL-1 is widely expressed in the central nervous system, particularly in regions associated with pain processing, emotion, and cognition, where it modulates neurotransmitter release [1, 5]. It plays a complex role in pain, exhibiting both pro- and anti-nociceptive effects depending on the route of administration and dosage [4, 10]. Beyond nociception, the receptor is involved in regulating anxiety, depression, substance abuse, and cardiovascular functions such as blood pressure [7, 9]. Therapeutic development focuses on ORL-1 agonists for non-addictive analgesia and heart failure, while antagonists are being investigated for treating mood disorders and Parkinson's disease [2, 7]. Its distinct signaling pathways make it a promising target for addressing conditions where classical opioids are ineffective or produce significant side effects [5, 10].

Other names

Nociceptin receptorNOP receptorOPRL1Kappa-type 3 opioid receptorOrphanin FQ receptorNOPrNOCIRKOR-3OOR

Agonism, Antagonism, Partial agonism; activation leads to inhibition of adenylate cyclase and voltage-gated calcium channels while activating potassium channels, resulting in neuronal hyperpolarization.