The Neurochemical Basis for Opiate Effects

Instructor: Ashley Dugger

Ashley is an attorney. She has taught and written various introductory law courses.

Opiates block pain signals to the user's brain while also stimulating pleasure signals. Opiates accomplish this by affecting neurotransmitters. This lesson explains the neurochemical basis for opiate effects.


You may have heard of opium. It's an ancient drug made from poppy seed pods. Opium was typically smoked, and was often used in rituals before becoming popular in many areas of the world as a recreational drug. Opium was prized for centuries as a painkiller and a sedative, but many cultures quit using opium as medicine due to widespread abuse of the drug.

There are many relatively newer drugs derived directly from opium and designed to have the same pain relieving effect. These are known as opiates. Codeine and morphine are opiates. Heroin is also an opiate, though heroin has been illegal in the U.S. since the mid 1920s.

Note that opiates are narcotics. Narcotics are a specific type of drug that works by affecting the user's brain and dulling the user's sense of pain. Opiates block pain signals to the user's brain while stimulating pleasure signals.


Let's take a closer look at how opiates affect the user's brain. Opiates work by influencing the user's neurotransmitters. Neurotransmitters are naturally occurring brain chemicals that communicate information throughout the user's brain and body. People have many different types of neurotransmitters. For example, one type of neurotransmitter tells your eyes to cry when you're sad, and another type tells your stomach to growl when you're hungry.

Neurotransmitters conduct signals between neurons and receptors. A neuron produces and sends a message, and a receptor receives the message. Signals can't be sent between a neuron and a receptor without the use of neurotransmitters because the two don't connect. There's a tiny space in between each neuron and receptor known as a synapse. Neurons send neurotransmitters into the synapses. The neurotransmitters are then accepted by and attached to receptors.

Neurons and receptors are separated by synapses.

In fact, the human brain naturally contains special receptors designed to help opiates work. They are known as opiate receptors. These receptors are concentrated in the areas of the brain that recognize pleasure and reward. The same receptors are also concentrated in areas of the body that recognize pain, such as the brainstem and spinal cord.


Opiate receptors likely exist because the human body produces 'natural opiates' known as endorphins. Endorphins are neurotransmitters that are released when the body experiences pain or stress. They work to calm the brain. Endorphins attach to the opiate receptors.

Depending on how much stress or pain a person experiences, sometimes more endorphins are released than can attach. This causes a traffic jam of endorphins in the synapse area, which blocks other signals from passing through. The neurons will temporarily stop 'firing', or trying to send messages into the synapse. This hinders pain signals and can bring about an overall numbing effect.

The pain relieving effect of opiates is achieved by mimicking endorphins. Opiate molecules flood into synapses and attach to opiate receptors, thereby blocking pain signals.


Opiates also influence a neurotransmitter called dopamine. Dopamine is a naturally occurring chemical that releases into the brain to bring about feelings of pleasure and reward. For example, dopamine releases into your brain when you laugh at a funny joke or when you eat your favorite dessert. It's a special type of neurotransmitter, because it works to both stimulate and calm the brain at the same time. Other neurotransmitters do one or the other, but not both.

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