Physiology of pain addiction; behavioural effects

Addiction is a condition that arises when a being consumes substances or engages in activities that can be pleasurable at first, but the prolonged ingestion or act of which becomes a necessity. It emerges by the search of the ‘euphoric’ feeling a substance or activity brings with it. This feeling is the cause of the increase of the level of the striatal dopamine neurotransmitter. Users may not be aware that their compulsive behaviour is out of control and also once a being is addicted an entirely separate set of events or stressors may sustain and maybe amplify the addiction. Addiction can eventually lead to abuse. When relating addiction to pain, it is actually the endorphins released in the system which aid the dopamine release and gets a being addicted, forming a dependency on their release.

Pain

Pain is a feeling of discomfort, distress or even agony depending on how severe it is. It has been defined as a biopsychosocial phenomenon that includes sensory, emotional, cognitive, developmental, behavioral, spiritual, and cultural components. (Salsitz, 2015) It is part of the body's defense system, producing a reflexive retraction from the painful stimulus, and protects the affected body part while it heals, and also avoid that harmful situation in the future. Pain can be either acute or chronic. Both types can be intense but chronic is the type of pain that lasts much longer, while acute pain is short lived. Pain stimuli starts from an electrical impulse from sensory receptors of the skin - nociceptors - to the spinal cord, acting as a relay center. The electrical impulse can be suppressed or enhanced before going to the brain. The brain then, produces several different neuroreceptors - such as glutamate - which then cause an impulse and reaches the thalamus and after the brain cortex.

Pain management

Pain management can be natural or artificial

Natural pain management

One of the main types of these endogenous opioids are beta endorphins. These are neuropeptides, which possess morphine like effects and are involved in the processes which bring happiness to a being - maybe even give a euphoric feeling. This is the part of the process which can get addicting. Physiological stressors such as pain, stimulate the synthesis of the the corticotroponin-releasing hormone (CRH) in the hypothalamus. This hormone is the one which triggers the anterior pituitary gland to synthesise the beta-endorphins. They are synthesised from their precursor protein proopiomelanocortin (POMC) along with other hormones such as the alpha-melanocyte stimulating hormone (MSH) and the adrenocorticotropin (ACTH). Beta-endorphins are also stored in the anterior pituitary. When there are enough beta-endorphins a negative feedback inhibits the further production of CRH.

Beta-endorphins act in both the peripheral and the central nervous system. They produce analgesia by binding to opioid receptors (usually the mu subtype). They bind to the receptors at both the presynaptic and postsynaptic nerve terminals but they mostly exert their effect through the presynaptic binding. In the peripheral nervous system (PNS), a cascade of reactions is induced after binding, which result in the inhibition of tachykinins release. These proteins - an example being substance P - are involved in the transmission of pain. In the central nervous system (CNS) the beta-endorphins inhibit the release of GABA, an inhibitory neurotransmitter, which then results in the overproduction of dopamine - a compound associated with pleasure (Sprouse-Blum et al., 2010).