Definition
Opioid receptors are receptors located in the cell membrane coupled with G proteins having as ligand an opioid (derived from the word opium).
Description
There are 4 subtypes of opioid receptors:
- Delta (δ)
- Kappa (κ)
- Mu (μ)
- Nociceptive receptors
Delta receiver
Location
- In the brain
Function
- Analgesia
- Antidepressant effects
- Physical dependence
Kappa receiver
Location
- In the brain
- In the spinal cord in the gelatinous substance
Function
- Spinal cord analgesia
- Sedation
- Myosis
- Inhibition of ADH hormone release
Mu Receiver
Location
- In the brain,
- In the spinal cord at the level of the gelatinous substance
- In the digestive system
Function
Depending on the subtype of μ receptors:
- Supraspinal analgesia
- Physical dependence
- Respiratory depression
- Myosis
- Euphoria
- Reduced motility of the gastrointestinal tract
- Physical dependence
- Nociceptive receptor
Location
- In the brain,
- In the spinal cord
Function
- Anxiety
- Depression
- Appetite
- Development of tolerance to μ-receptor agonists