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Current time:0:00Total duration:11:10

Video transcript

one popular way to treat depression is with antidepressants and these are drugs that help to relieve the symptoms of depression but before I talk about them I want to quickly go over neural transmission so here we have a neuron and neurons receive messages through their dendrites which are these branching structures here and then that electrical signal is sent down the axon to the axon terminals at the end and here it meets up with the dendrites of the next neuron down the line but these cells aren't really touching and the electrical signal the action potential it can't actually jump between these cells so how does the message get from one cell to the next when the action potential reaches the axon terminal the electrical signal has actually changed into a chemical signal and here's how it works the action potential triggers the cell to release vesicles full of chemicals called neurotransmitters and the vesicles these kind of cellular sacks they dock with the cellular membrane and the neurotransmitter spills out into the synapse which is what we call the space between these two cells and once there the neurotransmitters bump around and they can dock onto receptors on the next cell and when they do this triggers an electrical signal in that next cell and the antidepressants that we are going to be talking about today work on this synaptic level as do many other medications because by increasing or decreasing the amount of available neurotransmitter in the synapse medications can make it more or less likely that a message will be triggered in the next cell and depression itself seems to work on this level studies have suggested the depression might be caused by low levels of certain neurotransmitters called monoamine neurotransmitters and this includes serotonin norepinephrine epinephrine and dopamine and different theories disagree about the relative contributions of each one but this is something I want you to keep in mind when we talk about how these medications work because all of the antidepressants we're going to cover in this video work by trying to correct this imbalance they all caused an increase in the levels of these neurotransmitters but they do it using very different mechanisms so we're going to cover three classes of antidepressants monoamine oxidase inhibitors or Mao is tricyclic antidepressants or TCAs and selective serotonin reuptake inhibitors or SSRIs so let's start off with these Mao is and the clue to how these antidepressants work is in the name monoamine oxidase is an enzyme that breaks down neurotransmitters that isn't stored in vesicles so it's kind of like cellular housekeeping monoamine oxidase inhibitors are drugs that inhibit the actions of monoamine oxidase so by inhibiting this enzyme it actually increases the amount of neurotransmitter that is capable of being released into the synapse and more neurotransmitters in the synapse increases the likelihood that they will dock onto the postsynaptic cell and cause an action potential the next type of antidepressants are tricyclic antidepressants and instead of being named for what they do these drugs are named for how they look and I have a few examples here and you can tell that all of them have this three ring structure so try for three and cyclic for the Rings and tricyclics work by increasing the levels of two specific neurotransmitters norepinephrine and serotonin but the way that they do this is very different from Mao Weis instead of stopping an enzyme from breaking down these neurotransmitters TCAs work by interfering with a very different housekeeping mechanism called reuptake so much like you your body likes to recycle it likes to be efficient and this is even true at the neuronal level after the neurotransmitter has released into the synapse your body doesn't get rid of it instead it recycles it by taking it back up into the presynaptic cells through these reuptake channels and then it can be repackaged into vesicles and released again TCAs work by blocking these or reuptake channels and the result of this is that the neurotransmitter stays in the synapse longer which then increases the likelihood that it will dock on to a receptor on the postsynaptic cell and trigger an potential SSRIs or selective serotonin reuptake inhibitors they work the same way they work by blocking reuptake channels but instead of blocking them for both norepinephrine and serotonin like TCAs they only block reuptake for serotonin and only for very specific serotonin receptors so like Mao is here we have a situation where the name of the drug is a description of what the drug does and I think of all of these antidepressants SSRIs are probably the ones that you are most familiar with because this class of drugs includes fluoxetine which is also known as Prozac so we have three classes of antidepressants and a question you might have is how do doctors know which one to prescribe and your natural answer might be that they should prescribe the one that works best but it turns out that actually all of these medications are equally effective as antidepressants so maybe you think okay if we can't differentiate by effectiveness maybe we can differentiate by side-effects and this is where the main difference is lie Mao is and TCS are the oldest antidepressants they are what we call first generation antidepressants but because they are the oldest they tend to have more side effects than more recent drugs like SSRIs which are considered to be a second class antidepressant Mao is in particular are notorious for having a lot of side effects and this stems from the fact that Mao is affect a lot of different things remember we said that they affect all of the monoamine neurotransmitters but we also have to remember that these drugs don't just increase available neurotransmitters in the brain they do it in the entire body as well and this can cause a lot of different side effects for example Mao is wind up inhibiting a process in the liver that helps to metabolize medications and as a result people taking them need to be very careful when taking other prescription and non-prescription medications and this is something that you might have been aware of if you have ever paid attention to drug commercials many of them note things like people taking mao i should not take drug X or talk to your doctor if you are taking mi OS and the reason behind this is that if your body can't break down certain drugs it might lead to a dangerous buildup of those drugs in your body which could potentially be life-threatening but mio eyes don't just prevent the breakdown of certain medications they prevent the breakdown of certain foods as well I don't want to get too much into this but I would definitely recommend that you google the list of foods that people on ma Weis can't eat because it is pretty long it includes all fruits alcohols dairy some meats the list is very long and actually the diet can be so restrictive that people sometimes stop taking the medication and because of these side effects Mao is are no longer a popular choice for treating depression although they are still used when an individual has not benefited from other treatments before when we talked about tcas we noticed that instead of working on all of the monoamine neurotransmitters like mao is we said that they only work on two of them norepinephrine and serotonin and because they are more specific in what they affect they also have fewer side effects however for some individuals the side effects that they do have can be severe TCAs can sometimes affect things aside from norepinephrine and serotonin things like histamines and this can lead to fatigue and sluggishness another problem is toxicity TCAs are very toxic at higher levels and someone could go into cardiac arrest if they accidentally or purposefully overdose on them so individuals taking TCS need to be carefully monitored by doctors especially individuals who might be at a higher risk for suicide and like in my eyes the severity of these side effects make it so that tcas are not always the first choice when prescribing antidepressants although they are prescribed when people aren't successful with other treatments and they are also prescribed for individuals with bipolar disorder along with other medications like lithium and this is because other antidepressants specifically SSRIs can sometimes trigger manic episodes and people with bipolar disorder and so tcas are generally a safe for option but this brings us to SSRIs and with the exception of very specific cases like bipolar disorder this class of antidepressants are generally the first choice for individuals seeking treatment for depression and this is because they are really effective like the other antidepressants but also because they have fewer side effects and this has to do with the fact that they are the most selective and what they act on but like the other antidepressants they aren't side-effect free because they also work everywhere in our brain and our body and so there are some side effects and these can include sleeping problems weight gain and sexual dysfunctions and while these are not life threatening these side effects could have a negative impact on a person's quality of life there is one exception to this life-threatening clause though and that's a condition called serotonin syndrome and it's rarely occurs for people who are taking SSRIs on their own but it can become a problem if they are combined with other substances that also increase serotonin so I've talked about these three classes of antidepressants but there are other newer substances that are also on the market now some of them are combined SSRIs and SNRIs so they block reuptake for both serotonin and norepinephrine but only for very specific types of each and so I generally like to think about them as more restrictive TCAs so they get all of the benefits of TCAs with fewer side-effects another new kind of antidepressants RN dris norepinephrine and dopamine reuptake inhibitors and also ND ras norepinephrine and dopamine releasing agents so one blocks reuptake of norepinephrine and dopamine and the other triggers additional release of norepinephrine and dopamine but both result in an increase of these neurotransmitters in the synapse and both of these drugs are really promising and I'm sure that the only increase in popularity as time goes on but I really wanted to mention them here because I think that they challenge our cultural narrative of depression being caused by a decreased level of serotonin because these drugs relieve the symptoms of depression without influencing serotonin levels at all and that's just something to keep in mind because as our knowledge of this topic increases how we think about depression from both a medical and cultural standpoint will change as well