An Intro To Your Brain’s Opioid System – September 2014 – by Joe Cohen
The brain opioid systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, and the control of food intake (R).
There are four opioid receptors in our brain:
- mu-opioid (MOR),
- kappa-opioid (KOR),
- delta-opioid (DOR)
- nociceptin (NOP).
Increasing these receptors or the molecules that bind to them will produce an opioid high.
Activation of the mu receptor by a substance such as morphine causes sedation, euphoria and decreased respiration (R).
Individual differences in the function of the mu-receptor system predict personality traits that confer vulnerability to or resiliency against risky behaviors such as the predisposition to develop substance use disorders (R).
Activation of delta receptors produces some pain relief, although less than that of mu-opioid activators. (R)
Kappa activation actually produces a bad mood (dysphoria), some pain relief (analgesic), urination (diuretic) and in high dosages produce hallucinations (R).
Activation of the KOR opposes many of the effects of the MOR and can prevent addiction to morphine, alcohol, and cocaine.
It can cause an appetite increase and is activated by stress (R).
Ketamine, oxycodone, morphine and menthol all bind to KOR.