The HumanNervous System

Part 1

People talk about seeking that hit of dopamine as if this neurotransmitter is an internal euphoria producing drug. There are differences, some say, between natural dopamine, from healthy activities, especially outside, and artificial dopamine from TV, their phones, and drugs.  It is true that dopamine affects how the brain processes pleasure and reward, but the real story is more complicated, and more interesting.

Let’s get the basics first, and even if you know this, a minute reviewing never hurts. Neurons are nervous system cells that communicate with one another and target tissues by releasing chemicals into the synaptic cleft, the gap between neurons. These chemicals are neurotransmitters, and dopamine is one example.

Dopamine is a catecholamine, which is a family of neurotransmitters and hormones that also include norepinephrine, and epinephrine (adrenalin) which initiate our flight or fight responses.

Our autonomic nervous system, specifically the sympathetic division of the autonomic nervous system, uses norepinephrine and epinephrine to increase our heart rate, increase blood flow to our muscles, and increase our attention. They increase our awareness,  our survival instinct. This survival response is tied to motivation, reward, and locomotion, tied to dopamine, by chemical structure. Survival is rewarding.

Back to our story about dopamine. Some neurotransmitters cause an increase in firing of the next neuron, and some cause a decrease in firing, so sometimes they are referred to as excitatory and inhibitory neurotransmitters. Dopamine’s cousins generally cause excitatory reactions, but not always. The specific action of the neurotransmitter is determined by the receptor on the next neuron, called appropriately the postsynaptic receptor. The neurotransmitter docks with a receptor and the receptor initiates the response. Here is where the complications kick in.

There are at least 5 dopamine receptor types, and they are currently organized into two families, called D1 and D2. The D1 family of receptors causes excitation (increasing firing rates), and the D2 family generally causes inhibition (slowing down firing). These are the most common receptors in the brain. Dopamine can put on the gas, or it can put on the brake, and back and forth.

The D1 receptors in the brain are involved in learning, memory, attention, and reward. There is a dark patch of cells that look like two stripes on the midbrain called the substantia nigra, meaning dark substance. These are very easy to see in dissection of the brainstem and contain D2 receptors. These receptors help smooth out our movements. Parkinson’s disease patients have depleted dopamine in this region. D2 receptors are also involved in thinking and emotion.

As you can see, dopamine is important to our regulation of movement, mood, regulation of our motivation and attention, and these things are linked to our survival, and they are linked to our everyday behavior.

Now for more complication. After experiencing intense pleasure from an activity, the brain will reduce the number of dopamine receptors, or their sensitivity, which will reduce the pleasure response to that activity. Now you need more of that activity to get the same neurological response – the pleasure. After a while, you need more of that activity just to feel normal, forget about the pleasure.

It is well documented that addictions are linked to dopamine activity, which increases and sustains motivation through cravings, for example. Dopamine is the neurophysiological cause, the proximal cellular cause, and its regulation is the response to addiction, but it is not responsible for the addiction. That’s behavior. Someone’s behavior is responsible for the addiction.

Here is why the natural (for example an outdoor activity that is rewarding) and artificial (for example drugs) means of dopamine production are meaningless. They are neurologically the same. They create the same motivations and rewards, the same strong connections between an activity, a behavior, and a feeling.

Dopamine activity is not only linked to drug use, gambling, and risky behavior, which are familiar addictions, but also from watching TV or looking at your phone. To almost no one’s surprise, viewing short videos on your phone is highly addictive. The number of videos you need for the same response increases, as does the speed at which you scroll between them. You can find documentation of this, and other reliable literature at the free National Institute of Health website.

You didn’t do it, whatever it might be, for “the dopamine”. You are not addicted to “the dopamine”, you are addicted to the activity, whether that is you interacting with a drug or with your phone or other activity. We use expressions like “I need a hit of dopamine” or “I’m just a dopamine junky” as a shortcut, a way to short the infinite regress of the cause of our behavior. My brain and my environment made me do it. Relying on this myth robs us of real explanation, robs us of knowing what and who we are. Robs us of the means of communicating about how we feel.

Your brain didn’t do it, you used your brain to do it.