Neuro-101

So… what are these neurochemical pathways? How (and perhaps why) do they affect our moods and behaviors?

Norepinephrine (aka – adrenaline!), endorphin (the body’s own endogenous morphine), serotonin (chicken soup for the brain), oxytocin (a legal “hug drug…”) and, of course, dopamine — most people have at least heard of many or all of these. But what are they, where do they come from, and what do they do? More importantly, if they make us happy, how can we trigger them naturally?

To understand all this, we need to go back in time a bit, say half a billion years or so… A long time ago, yeah. So, (at least some of) these pathways have been around a while. Let’s start with dopamine. Invertebrates began generating and deploying this protein as a key chemical in the primitive nervous system for regulating movement. As nature is resourceful, in areas of the CNS (central nervous system) that were geographically separated from one another, the same chemical could be put to use for other functions. Invertebrates eventually evolved a mechanism in the CNS where dopamine became integral to rewarding certain behaviors and for initiating the creation of long-term memories about these behaviors that increased the animal’s rate of survival. This formed the early beginnings of an emotional system: to reward an organism with a positive sensation and promote formation of a lasting memory for how to elicit this feeling when an action or event improved the organism’s likelihood to live long enough to reproduce and leave copies of its DNA in future generations.

But neurotransmitter chemicals in the CNS don’t act alone. In the case of dopamine, one of the early precursors to generating the “dopamine hit” that encouraged a behavior was norepinephrine, a brain-specific variant of a substance called epinephrine, which most people know as adrenaline…

This cascade of events — norepineprhine to dopamine to good feelings to long-term memory — would result from a list of activities important to survival that scientists fondly refer to as “the four ‘f’s” – fighting, fleeing, feeding, and fu… ornicating! So, the early insect brain may have been the place where our current symphony of emotions first took hold.

Today, people often talk about dopamine as the “feel good” chemical in the brain. That description is only partly true. In the case of the norepinephrine pathway, fighting and fleeing are rarely thought of as happy experiences, at least while they are occurring. But… if the animal succeeds in the fighting or the fleeing, in no small part from the extra strength, altertness and energy provided by the adrenaline shot, a huge hit of dopamine is released in the aftermath — ahhhh! Seems like the same ahhhh feeling may be useful to survival after finishing up with the more pleasant two ‘f’s, as well. So, there we have it, the early beginnings of the emotional center known today as the mesolimbic system.

This norepinephrine-to-dopamine pathway isn’t a simple on/off switch, though. The action of neurotransmitter to nerve cell is more subtle than that. Basically, when electric signals are sent through a neuron — the wiring of the CNS — at the end of that neuron are vesicles filled with neurotransmitter chemicals. A strong enough signal will cause them to be released into the synaptic gap, where they can float over to what are known as receptors at the start of another neuron. If enough of the neurotransmitter molecules dock into the receptors with the proper shape to receive them, then the next nerve cell fires an electric signal. This is how messages travel through the CNS. So more intense experiences cause increased release of neurotransmitters which cause more nerve cells to fire which creates a stronger signal — and a stronger emotion. And likely a stronger memory to encourage the behavior in the future.

Well, it looks like the source of the “adrenaline high” common to perceived (or real) risk during outdoor adventure sports is the result of activating the “fight or flight” reaction from the primitive brain: make it to the bottom of a steep hill or the end of the big wave still standing, and — BOOM! — a big adrenaline release translates to bigger dopamine hit. But are we really just a bunch of adrenaline junkies for participating in these activities? Maybe a little… but there’s more to it still!

In the case of mountain biking and surfing, you still need to get to the top of the hill to descend that sweet singletrack, or paddle through the surf to catch that killer wave in the first place. This can take quite a bit of effort. If the effort becomes anaerobic, where energy burn rate exceeds oxygen supply to the muscles, then lactic acid is released — pain! — and the body reacts by releasing  endorphin, scientifically known as an an endogenous opioid neuropeptide. The pain goes away (or at least subsides a little…) and the brain gets rewarded, as well, with a slow and steady release of dopamine — ahhhhh! Mountain biking and other activities can also release endorphin during less strenuous aerobic activity — think a long, steady climb — but that takes a bit more time, around a half hour or more! Gotta pay to play, though. Long live long climbs!

So, we’ve got the norepinephrine and endorphin pathways to dopamine. Are there others? Yep! Next one to understand is called serotonin, which, like dopamine, is used for multiple functions in the CNS, but in terms of the mesolimbic emotional system, it’s sort of like the “chicken soup for the brain,” and gives us (and probably other animals) an overall sense of well-being, along with, of course, a slow-release dopamine hit! Fortunately for those of us who participate in outdoor adventure sports, vigorous exercise and simply being outside in nature are great ways to release more serotonin into the brain. Of course, you could get the serotonin release by walking calmly along the beach or through the forest, but some of us like mixing our cocktails a bit stronger — a shot of adrenaline with a chaser of dopamine, all accompanied by a fine elixir of serotonin.

Let’s continue the technical discussion with our warm fuzzy neurotransmitter of interest — the oxytocin pathway! It’s sometimes called the body’s own hug-drug is because it is released when we feel a bond of kinship or strong camaraderie with others. What is it’s origin? Apparently, it’s one of the key brain differentiators between mammalian and non-mammalian brains, and one of the primary reasons mammals (at least mothers) care for their young. Once again, it has multiple uses, such as inducing labor contractions, stimulating milk production, and, of course, infant-maternal bonding. Experiments with mice bred with a “knock-out” gene that blocked production of oxytocin showed that the mothers wouldn’t care for their young — and the infant mice died… For most mammal species, this chemical is present in large quantities only in females, but in the case of humans, it is generated in significant quantities for both men and women. It appears to be a key neurotransmitter in the formation of long-term bonds for both sexes — mother/father/child, extended family, tribe.

So what does oxytocin have to do with mountain biking, surfing, skiing and the like? Directly, not much… But these activities are much more rewarding when done with others of a like mind, and the camaraderies that quickly form while participating in high-risk adventures are compelling and obvious to those involved. So… ride, slide and glide then hang out with the tribe!

This is nowhere near a comprehensive list of all the neurotransmitters that work in concert to keep our brains firing smoothly. Scientists have isolated over 40 of them so far! But a few of the more notable ones include: GABA (gamma-aminobutyric acid), a widely-dispersed inhibitory chemical/receptor combo (and one easily affected by alcohol — and hence, drinking’s propensity to lower inhibitions…), glutamate, a pervasive (and usually) excitatory one, and, finally, anandine, the neurotransmitter chemical used by the endocannabinoid system (ECS) — a more recently discovered neurotransmitter/receptor system that, among its many natural purposes (like giving you the munchies… ;-),  contributes to exercise-induced euphoria (as does endorphin), as it is released during sustained aerobic activity. And, yes, THC (tetrahydrocannabinol, the active ingredient in certain now-legal herbs) activates the endocannabinoid system — but in a much stronger and longer lasting manner than anandine.

But the primary takeaway is this: to increase your level of contentment, go outside and paddle, pedal, and schuss your brains out — then share these incredible moments with others! Your body — and brain — will thank you…