Kappa-type opioid receptor (OPRK1) (OPRK1)

The kappa-type opioid receptor (OPRK1), historically designated as the OP2 receptor, is a G protein-coupled receptor (GPCR) that primarily couples to inhibitory Gi/Go proteins to modulate adenylate cyclase activity and ion channel conductance. It is widely expressed throughout the central nervous system, particularly in the limbic system, hypothalamus, and spinal cord, as well as in peripheral sensory neurons. Activated predominantly by endogenous dynorphin peptides, the receptor plays a critical role in the regulation of nociception, stress, and mood. While agonists of the receptor provide potent analgesia and are effective in treating pruritus, their clinical utility has been hampered by centrally mediated adverse effects such as dysphoria and hallucinations. Modern drug development focuses on peripherally restricted agonists for chronic itch and selective antagonists as novel treatments for treatment-resistant depression and substance use disorders. Unlike mu-opioid receptors, OPRK1 activation does not typically lead to significant respiratory depression or physical dependence, making it a distinct target for non-addictive therapeutic interventions.

Other names

Kappa-type opioid receptorKappa opioid receptorKORKOPOP2Opiate receptor kappa-1KOR-1OPRK

Agonists activate the Gi/Go signaling pathway, inhibiting adenylate cyclase to decrease cAMP levels, reducing calcium influx, and increasing potassium efflux, which collectively suppresses the release of excitatory neurotransmitters (e.g., glutamate, substance P) to provide analgesia and antipruritic effects. Antagonists block the interaction of endogenous dynorphins with the receptor, thereby counteracting the dysphoric and aversive states associated with chronic stress and depression.