Neurotransmitters and Addiction


Neurotransmitters are chemicals within the nervous system that communicate information throughout our brain and body. They send signals from one neuron to another neuron. The brain uses neurotransmitters to tell your lungs to breathe, your heart to beat, and your stomach to digest. They also affect your mood, focus, and motivation.

Endorphins are the body’s natural neurotransmitters and they typically reduce pain or modulate mood. All addictive drugs mimic the actions of some neurotransmitter; in the case of heroin that neurotransmitter is probably endorphin. Ironically, the word “endorphin” is short for endogenous morphine, which means morphine made from within the body.

Neurons and Interneurons

What we’re looking at here are neurons. Your average neuron consists of a cell body, an axon and dendrites. The space in between one neuron and the other is called a synapse. That is where signals from one neuron pass to another. Since the two neurons are not connected, the neuron on the top must release chemicals (neurotransmitters) from tiny vesicles into the synapse.

Opioid Interneuron

This is where it gets interesting. Neurotransmitters have one of two possible functions, either to excite or inhibit a response. GABA neurotransmitters are considered inhibitory neurotransmitters. So after GABA neurotransmitters cross the synapse, they bump into and activate GABA receptors on Dopamine dendrites. The GABA receptors then send inhibitory signals to the Dopamine nucleus – to not release Dopamine. However, when heroin is consumed, the opposite occurs. But why does that happen?

The answer is absolutely fascinating. Heroin enters the body and quickly turns into 6-monoacetylmorphine (6MAM) and a little Morphine. Both 6MAM and Morphine bump into and activate opioid receptors on GABA neurons. Both 6MAM and Morphine act like inhibitory neurotransmitters themselves and suppress GABA neurons, to greater or lessor degree depending upon dosage. 6MAM and Morphine slow the rate of GABA release, which results in disinhibition of Dopamine. The released Dopamine travels down the axon and into a different synapse, where it bumps into Dopamine receptors of a third neuron and around and around the brain it goes.