Classically, Ој-receptors are presynaptic, and inhibit neurotransmitter release through this mechanism, they inhibit the release of the inhibitory neurotransmitter GABA, and disinhibit the dopamine pathways, causing more dopamine to be released. Ој-receptors are the main receptor through which morphine acts. Addison disease), the level of endorphins also increases slightly.Д«eta-endorphin has the highest affinity for the Ој1- opioid receptor, slightly lower affinity for the Ој2- and Оґ- opioid receptors and low affinity for the Оє1- opioid receptors. In situations where the level of ACTH is increased (e.g. The behavioural effects of beta-endorphin are exerted by its actions in the brain and spinal cord, and probably the hypothalamic neurons are the major source of beta-endorphin at these sites. The physiological importance of the beta-endorphin that can be measured in the blood is far from clear: beta-endorphin is a cleavage product of POMC which is the precursor hormone for adrenocorticotrophic hormone (ACTH). The beta-endorphin that is released into the blood cannot enter the brain in large quantities because of the blood-brain barrier.

Д«eta-endorphin is released into the blood (from the pituitary gland) and into the spinal cord and brain from hypothalamic neurons. Importantly, recent studies have demonstrated that diverse animal and human tissues are in fact capable of producing morphine itself, which is not a peptide.

Snyder of the United States found what Eric Simon (who independently discovered opioid receptors in the brain) later termed 'endorphin' by an abbreviation of 'endogenous morphine', which literally means ' morphine produced naturally in the body'. Around the same time in the calf brain, Rabi Simantov and Solomon H.John Hughes and Hans Kosterlitz of Scotland isolated - from the brain of a pig - what they called enkephalins (from the Greek ОµОіОєОП†О±О»ОїП‚, cerebrum).Opioid neuropeptides were first discovered in 1975 by two independent groups of investigators. However, this term does not occur in the medical literature. The term endorphin rush has been adopted in popular speech to refer to feelings of exhilaration brought on by pain, danger, or other forms of stress, supposedly due to the influence of endorphins. It consists of two parts: endo- and -orphin these are short forms of the words endogenous and morphine, intended to mean 'a morphine-like substance originating from within the body.' The term 'endorphin' implies a pharmacological activity (analogous to the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical formulation. In other words, they might work as 'natural pain killers.' Using drugs may increase the effects of the endorphins.

They are polypeptides produced by the pituitary gland and the hypothalamus in vertebrates, and they resemble the opiates in their abilities to produce analgesia and a sense of well-being. Proopiomelanocortin (adrenocorticotropin/ beta-lipotropin/ alpha-melanocyte stimulating hormone/ beta-melanocyte stimulating hormone/ beta-endorphin)Д®ndorphins are endogenous opioid biochemical compounds.

Endorphin receptors