Question

Image of heroin and its synaptic mechanism with endorphins as its neurotransmitter system

Answer 1

Endorphins are chemicals produced by the body to relieve stress and pain. Endorphin levels go up when a person exercises, goes into labor, or is stressed out. Although they seem to be triggered by stress, endorphins can do more than relieve pain, they actually make us feel good.  They work similarly to a class of drugs called opioids. Opioids relieve pain and can produce a feeling of euphoria. The pleasure effect associated with endorphins is in part related to the increased dopamine production. Heroin produce effects that are similar to those produced by the neurotransmitters endorphin.

Once heroin enters the brain, heroin binds to and activates specific receptors in the brain called mu-opioid receptors (MORs). When MORs are activated in the reward center of the brain, they stimulate the release of the neurotransmitter dopamine. These receptors, through second messengers, influence the likelihood that ion channels will open, which in certain cases reduces the excitability of neurons. This reduced excitability is the likely source of the euphoric effect of opiates.This euphoric effect also appears to involve another mechanism in which the GABA-inhibitory interneurons of the ventral tegmental area come into play. By attaching to their mu receptors, exogenous opioids heroine reduce the amount of GABA released. Normally, GABA reduces the amount of dopamine released in the nucleus accumbens. By inhibiting this inhibitor, heroine ultimately increase the amount of dopamine produced and the amount of pleasure felt.