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. 2020 Sep 28;10(10):1376. doi: 10.3390/biom10101376

Table 1.

Opioid receptors and their functions.

Opioid Receptor Subtypes Previous and Unofficial Names Effects of Activation
µ µ1, µ2, µ3 Mu receptor/MOP/OP3/MOPr/opioid receptor, mu 1

  • spinal and supraspinal analgesia

  • respiratory and cardiac depression

  • euphoria

  • sedation

  • physical dependence

  • tolerance

  • changes of smooth muscle tone

  • decreased gastrointestinal motility

  • urinary retention

  • pruritus
δ δ1, δ2 DOP/DOR/OP1/Delta receptor/DOR-1/DOPr

  • spinal and supraspinal analgesia without respiratory compromise

  • antidedepressant effect

  • antianxiety effect

  • decrease of colonic transit time
κ κ1, κ2, κ3 KOR-1/Kappa receptor/OP2/KOP/KOPr

  • spinal and supraspinal analgesia

  • miosis

  • psychotomimetic effects (dysphoria, agitation)

  • sedation without pronounced respiratory depression, euphoria or gastrointestinal effects
Nociceptin receptor ORL1 N/OFQ receptor/OP4/KOR-3/NOCIR/kappa3-related opioid receptor/MOR-C/nociceptin receptor ORL1/XOR1/NOP-r/nociceptin/orphanin FQ receptor/NOPr

  • analgesia at the spinal level

  • reduction of locomotor activity

  • impairment of memory

  • increase of food intake

  • anxiolytic effect

  • increase of water diuresis

  • stimulation of immune response