Endorphins

Endorphins (contracted from endogenous morphine)[1][2][3] are peptides produced in the brain that block the perception of pain and increase feelings of wellbeing.

Endorphins are endogenous painkillers often produced in the brain and adrenal medulla during physical exercise or orgasm and inhibit pain, muscle cramps, and relieve stress.

[4][5][6][7] Opioid peptides in the brain were first discovered in 1973 by investigators at the University of Aberdeen, John Hughes and Hans Kosterlitz.

[11] Research during this time was focused on the search for a painkiller that did not have the addictive character or overdose risk of morphine.

[15] In 1976, Choh Hao Li and David Chung recorded the sequences of α-, β-, and γ-endorphin isolated from camel pituitary glands for their opioid activity.

[18] Wilhelm Feldberg and Derek George Smyth in 1977 confirmed this, finding β-endorphin to be more potent than morphine.

[32] β-LPH, a pituitary hormone with little opiate activity, is then continually fragmented into different peptides, including α-endorphin, β-endorphin, and γ-endorphin.

Endorphins inhibit transmission of pain signals by binding μ-receptors of peripheral nerves, which block their release of neurotransmitter substance P. The mechanism in the CNS is similar but works by blocking a different neurotransmitter: gamma-aminobutyric acid (GABA).

In turn, inhibition of GABA increases the production and release of dopamine, a neurotransmitter associated with reward learning.