Neurotransmitters! We hear all about them as we ponder “What causes depression?” and “What causes anxiety?” But just what are they – and what do they do? (And why should we care?)
In the midst of my anxiety and mood nightmare, it was important to me to understand the in’s-and-out’s of my ailments. As a counselor, keeping current on the biology of the mood and anxiety disorders remains a top priority. How else could I provide much needed explanations to my clients?
Yep, I’ll say it again – “Knowledge is power!” It also happens to be relief and healing. That said, let’s dig-in to the biological foundation of the mood and anxiety disorders, as we learn about neurotransmitters.
Our brains consist of some 100 billion neurons (nerve cells). Each and every one of them generates between one and 10,000 synapses (connections between neurons). So that would mean the number of potential synaptic connections in the brain is right at 40,000,000,000,000,000. That’s an astounding forty quadrillion!
Messages travel from neuron to neuron in the form of electrical potential. And to maintain this interconnectivity, during synapse such a message takes a one-millionth of a centimeter jump at speeds up to 260 miles-per-hour. Without neurotransmitters the jump can’t occur – or, perhaps, not as efficiently.
Neurotransmitters are stored in tiny vesicles gathered at the tip of a neuron’s axon, and they’re activated upon the arrival of electrical action potential. When activated, neurotransmitters pour out and spread across the synapse area (the cleft).
Once there, they’re active for between .5 and 1 millisecond. In this incredibly brief time-frame the neurotransmitters cross the cleft, binding to receptor molecules on the dendrite of the receiving neuron. The dendrite then conducts the electrical signal into the body of the neuron. Message sent and received!
So they’ve done their job. Neurotransmitters now have several potential fates, one of which is re-absorption by the molecular transporter of a pre-synaptic neuron – a process known as reuptake. Sound familiar? It ought to, as virtually all modern antidepressants inhibit neurotransmitter reuptake. And at least in theory, it’s all about maximizing the presence of neurotransmitter in a synapse, ensuring all is going according to design.
Neurotransmitters come in assorted types, with many variations within. Let’s take a peek at two classifications that loom large in the mood and anxiety disorders. Oh! When you read the physiological and cognitive functions these neurotransmitters impact, you’ll understand why side-effects are an issue with psychotropic medications.
- Serotonin: aka 5-hydroxytryptamine (5-HT), serotonin is derived from the essential amino acid tryptophan. Of our 5-10 mg supply of serotonin, 90% is located in the gut where it’s used to regulate intestinal movements. The rest is found in blood platelets and the brain. In the brain, serotonin impacts mood, emotion, learning, memory, aggression, sexuality, sleep, appetite, temperature regulation, sensory perception, metabolism, and more. Of great importance to us is serotonin’s working relationship with norepinephrine, which we’ll discuss next.
- Norepinephrine: aka noradrenaline, norepinephrine is a hormone and neurotransmitter synthesized from dopamine. As a neurotransmitter, norepinephrine influences mood regulation, dreaming, sleep, alertness, arousal, and learning. As a hormone, it impacts attention and impulsivity management. Norepinephrine is a huge player in how we respond to and manage stress, as it has direct influence upon our fight/flight response.
Now for that all important working relationship with serotonin. As serotonin levels are sufficiently maintained, so are levels of norepinephrine. So when supplies of serotonin run low, levels of norepinephrine increase in an effort to resolve the shortage. As serotonin levels rise, levels of norepinephrine recede in kind. Bottom-line: If sufficient levels of serotonin can’t be maintained, and norepinephrine can’t stimulate a boost, the presence of serotonin continues to plummet. And the result is thought to be mood and/or anxiety disorder woes.
- Dopamine: This neurotransmitter can be created by any of three amino acids, most notably L-Tyrosine. Dopamine plays a major role in reward-driven learning, so it makes sense that a variety of highly addictive drugs act upon the dopamine system. Within the brain, dopamine impacts functions such as behavior, cognition, motivation, punishment and reward, sleep, dreaming, mood, attention, working memory, learning, and voluntary movement.
- Glutamate: Given 90% of the synapses in the human brain involve glutamate, it’s our most abundant neurotransmitter. It’s an excitatory neurotransmitter, which means it’s action-generating. Glutamate is especially a factor during trauma and hypoglycemic (low blood sugar) events. It’s also involved in cognitive functions such as learning and memory. Glutamate is becoming an increasingly popular target for the development of depression-relieving medications. For example, GLYX-13, a revolutionary new antidepressant in the clinical trials process, targets the glutamate receptor NMDA.
- gamma-Aminobutyric acid (GABA): A cousin of glutamate (it’s actually synthesized from it), GABA is our most abundant inhibitory neurotransmitter. Its action is opposite to that of glutamate. GABA is directly responsible for maintaining muscle tone, and it also has sleep-inducing characteristics. Most important to us is it’s believed GABA has the ability to unlock and actually bring to life anxiety-inhibiting receptors on nerve cells. Oh, by the way – that’s why many sedating/tranquilizing drugs (e.g.: benzodiazepines) act by enhancing the effects of GABA.
So there you have it – a thumbnail on neurotransmitters. I know I tossed bunches of information at you; however, when it comes to “What causes depression?” and “What causes anxiety?” we need to be exposed to it. And it’s also important to understand the targets of the medications being used for the relief of the mood and anxiety disorders. For now, anyway, they’re neurotransmitters.
Knowledge is power? I sure think so…
image credit neurotransmitters interactive-biology.com
image credit synapse scienceblogs.com