 Good morning. The exam, the midterm is scheduled to go out tomorrow. However, we're still working on it. How many of you will be inconvenienced if instead, and it's due next Tuesday, how many of you will be inconvenienced if it goes out on Thursday rather than tomorrow? One of you. Okay. Good. Well, that's enough to make a difference. So we will try to post it by tomorrow or Wednesday at the latest. Okay. Good. After we post the midterm and until it's due, there will be no quizzes in class. Today's and the next lecture will be given by Ralph Adolph's. It'll be on the visual system. But today we are going to synthesize everything, most of the points that we have made so far in the course to talk about recreational drugs. So I actually bought the rights to show this cartoon from senior Wilkinson, who is a cartoonist from the Philadelphia Inquirer. She said to me, thank you for buying the rights, but tell me, is marijuana a gateway drug? This was about 10 years ago. I told her that probably if I knew then what I know now, I would not smoke marijuana and we'll find out why. But this is only one lecture on recreational drugs and next year, January 2017, I will give a course on neuropharmacology and we will talk in greater detail about drugs that act on the nervous system. We already know how a couple of these drugs work. We know that three of them are enzyme inhibitors, which you learned about in various courses and just the other day we learned about Viagra. And we know that three of them are also neurotransmitter transport inhibitors, Ritalin, appetite suppressants such as amphetamines and Prozac, which is fluoxetine. Unfortunately, candle does not have easy access to this material. It's scattered throughout candle. First, a disclaimer. Don't offer your pattern of prescription drug compliance as a result of this course and consult a medical professional for further guidance about prescription drugs. I'm not aware of all trends in current medical practice nor is Ralph Adolph's, neither of us are physicians and we cannot prescribe. Now there is a distinction between recreational drugs, addictive drugs, abused drugs and illegal drugs. For instance, caffeine could be termed recreational. It's probably not addictive in any of the usual senses of that term, nor abused, at least according to the definition of the National Institute of Drug Abuse. And it's certainly legal, but it certainly is true also that several of the drugs I'm going to discuss today are addictive, can be abused, and are in some cases illegal. So here's the constitution of nine drugs that we're going to discuss today and this little beaver crossed out means you don't have to remember their structures. We're going to discuss morphine, tetrahydrocannabinol, ethanol, caffeine, ketamine, actually one of its enantiomers, esketamine, LSD, nicotine, cocaine and amphetamine. Now some of you may have friends who use other recreational drugs and we could stop here and ask about those other recreational drugs and in some cases they act analogously to ones here. Would anyone like to offer the name of another one used by a friend or what have you? Okay, so let's go on. Just a reminder that most recreational drugs either arose or are derived from plant drugs. So here for instance is a picture of a coca harvest in Bolivia in the Andes. It's been going on for a long time. This is 1950. The coca leaves are the source of cocaine. And it is remains a large industry in the Andes and in South America to gather coca. These are coca leaves then from the coca plant. In fact, if we think about the source of the drugs on our list, here they are. Most of them come from plants. Morphine, of which heroin is a derivative, comes from the opium poppy, poppiver somniferum, the poppy that brings sleep. Tetrahydrocannabinol comes from two species of cannabis, the hemp plant. Nicotine, of course, comes from the plant whose Latin name is Nicotiana tobacco. Cocaine, we just showed you the coca plant. Amphetamine is synthetic, but I'll tell you an interesting story about that. Ethanol does not come from a plant but comes from fermentation from a yeast, Saccharomyces soradicia. LSD is purely synthetic. Caffeine comes from various species of the coffee plant or the tea plant. Enketamine is entirely synthetic. So again, we don't need to know these Latin names. Ting got its name from Jean Nico, who is the French ambassador to Portugal and Portugal and Spain, as you know from courses at Caltech, who were first to discover the West Indies. And in fact, the tobacco plant came to the attention of Europe when it was offered to Columbus's crew by the natives. Then about 50 years later, Jean Nico brought a sample of tobacco back to France. And he was honored for this by actually becoming part of the name of nicotine and there is a unique co in Paris. So the coca plant, amphetamine is synthetic, coffee and tea, although LSD derives from a molecules which are similar, which are found in the fungus ergot. And there is an interesting hypothesis that the fungus that gives rise to ergot actually infested grain in the Massachusetts Bay Colony during the particularly moist winters in the 1630s. And there is a theory published in a reputable journal that the Salem witch trials were triggered by people who accused other women of being witches while the accusers were under the influence of hallucinogens from ergot. This has not been proven in any sense, but is quite an interesting hypothesis. So one question becomes, if we look at the plant origins of many of these drugs, what selective advantage does making a recreational drug bring to a plant? Any question? Any suggested answers to that? So what selective advantage does a plant get from making a drug? Yes, just terrific. Now, if you could increase your voice by between six and three decibels, everybody in class could hear that. But I think that you've made a good point, nicotine is an insecticide, and therefore it would protect the plant against bugs or animals that would like to eat the plant. What you're suggesting. Yeah. Well, in fact, it is thought that the selective advantage of all of these drugs is that they protect the plants against herbivores. And that, and we and maybe cats and catnip are the only species that have learned to use these toxins to obtain pleasurable and recreational effects by limiting our ingestion of these toxins. So the average herbivore animal that eats plants does not know about limiting the input and so gets very sick or even dies after eating the plant. Any other suggestions? There have actually been some suggestions recently in reputable journals that the opposite can also be true, especially for caffeine and bees that actually insects are attracted to caffeinated plants, eat them more and are able therefore to spread the pollen more effectively. One more point. Notice that in every case here, we use the correct terminology for genus and species. It's italicized. The genus is capitalized, but not the species. There's no need to invent new terminology. This terminology and this use has been around for 300 years and biologists do it all the time. So another characteristic of nearly every drug that we looked at is that they have a nitrogen group. The only exception is THC tetrahydrocannabinol. The nitrogens in nearly every case have a pKa around 7.5. That is, they are partially protonated and partially unprotonated. And so for instance, for the case of cocaine, when one directly extracts cocaine from the plant using the solvents, it is in its free base form. Sometimes also called crack cocaine and when one treats the free base with an acid, the nitrogen gets protonated. But this reaction is reversible at neutral pH in a few milliseconds. And then you can treat with base ammonia or sodium bicarbonate and then heat to drive off the hydrochloric acid and you're left with the free base. And this is important because ingestion of most of the drugs is passive. It goes through lipid membranes. In fact, when one smokes tobacco, nicotine needs to pass through six cell membranes in its neutral, permanent form before it reaches the neurons of the central nervous system. Cocaine, when inhaled, also passes through six membranes. Typically it starts in the nose rather than in the lungs. So in its un-deprotonated neutral form, it can easily pass through membranes, gets into the blood and cerebrospinal fluid. And within milliseconds, it's in equilibrium with its protonated form. And the protonated form is, in fact, the active form that works on receptors. We learned about local anesthetics. They actually work from inside ion channels, get stuck in those ion channels, so they go through one more membrane, go into the cell as deprotonated, and then bind to the channel. To increase the amount of cocaine that they take, South American Indians have learned to use calcium hydroxide, lime, which is a base, to shift this equilibrium toward the deprotonated form. And in fact, there are also bases in cigarettes to help to shift this equilibrium, so that the first part goes quite rapidly. Any questions? Okay, so what about the targets? Which is really a major discussion of this course. Targets for recreational drugs. Well, we've discussed voltage-gated channels. They don't seem to be targets for any recreational drugs. We've discussed ligand-gated channels like nicotinic receptors and GABA receptors. They are targets for both ketamine and nicotine. We'll go into more details. We've discussed enzymes, which an enzyme is probably one of the targets for caffeine. It's an intracellular enzyme. We've discussed G-protein-activated channels as G-protein effectors. This is probably a target for alcohol. We'll get to that in a minute. We've discussed G-protein-coupled receptors, and these are the targets of some of the drugs, and finally neurotransmitter transporters. So we've discussed the molecules that are targets for these drugs. We've discussed how they get into the central nervous system. I just want to remind you of a slide that I've already showed you that neurotransmitter transporters are targets for the abused drugs such as ecstasy, MDMA, and the dopamine transporter is the target for abused drugs such as cocaine and amphetamine. However, antidepressants also bind to the serotonin transporter. These are the SSRIs, the selective serotonin reuptake inhibitors. You don't need to remember the trademarks, but you, like me, presumably have friends who have improved their disposition in their lives by taking SSRIs or molecules that act on other neurotransmitter transporters as antidepressants. And then you presumably also know people who have long-standing ADD or ADHD, attention deficit disorder, or attention deficit hyperactivity disorder, and control that using Ritalin or Dexadrin or Adderall. So these are very common in our society, and they are used medically as well as recreationally. Any questions? Okay. So each of them does a job that mimics or substitutes for an endogenous ligand. For instance, morphine or heroin substitute for an endogenous ligand, which is actually a small peptide. There's a family of them called the endorphins, literally endogenous morphines, and these are the enkephalins, several classes of these. THC also substitutes for, is an agonist and also substitutes for an endogenous agonist, anandamide. Nicotine is an agonist and has many of the same effects as acetylcholine, a point we've mentioned often in this course. Cocaine is an antagonist. It binds to a, it substitutes for dopamine. Amphetamine and derivatives can be either antagonists or false substrates mimicking noradrenaline, serotonin, and dopamine. Ethanol is unusual in many ways, and it acts in many ways, but it seems to be able to activate ion channels the way G-proteins do. LSD is an agonist, which acts on the same kinds of receptors as serotonin. Caffeine is an inhibitor. We discussed last time that it is in the G-protein pathway, and it acts on the same molecule that handles cyclic AMP. Ketamine is an antagonist and seems to block glutamate, seems to interact in the same pathway as glutamate. In more detail, I should point out that there's a caltech story involved here as well. Some of you have worked in or taken classes in the Alley's building. Alley's noted the properties of a plant called ephedra, again, genus species, which was highly useful against asthma. He synthesized amphetamine, which is synthetically related to ephedrine, coming from ephedra. It got the trademark benzedrine, and he patented this. He got a nice income from that patent, and the income from that patent helped to build the Alley's building at Caltech. He got his BS a while ago, his MS and his PhD, and he was on the Caltech faculty as a research associate for many years. So thanks to Gordon Alley's, we have the Alley's building with the help of the NIH, which helped to build it. If we look again at these drugs, and we ask detailed questions about their targets, the target for heroin and morphine is a G-protein coupled receptor, specifically a GI-coupled receptor. It is the mu-opioid receptor. The target for THC is also a G-protein coupled receptor, a GI-coupled receptor called the cannabinoid receptor. Opioid comes from the word for opium. Nicotine, of course, has the target of an agonist-activated channel, and its most sensitive target is a nicotinic acetylcholine receptor, because it's a sensitive target for nicotine, we call it nicotinic, and it happens to be the receptor consisting of alpha-4 and beta-2 subunits. The target for cocaine is a plasma membrane neurotransmitter transporter, which I showed you, the dopamine transporter. Amphetamine and its derivatives actually are very sly. They target both vesicular and plasma membrane neurotransmitter transporters. Remember, there are two transporters, we described this a couple of weeks ago. The particular target of amphetamines, in addition to the plasma membrane neurotransmitter transporter, is the so-called vesicular monoamine transporter, abbreviated happily enough, V-MAT. Again, ethanol is an outlier. It may activate a potassium channel. In fact, a G-protein-gated inwardly rectifying potassium channel called GERC-1 or 2, G-protein-gated inward rectifying potassium channel. And we discussed last time how you can activate these channels using excised patches in endogenously applied beta-gamma subunits of G-proteins. LSD's target is also a GPCR. This one happens to be linked to GQ. That is, it produces intracellular calcium. Formally, it is called the serotonin 5-HT2A receptor. As we remarked, there are lots and lots of G-protein-coupled serotonin receptors. The one that is most sensitive to LSD is this one. Caffeine's target is an enzyme, and as we discussed last time, it is cyclic AMP phosphodiesterase. One of the cyclic GMP phosphodiesterases we discussed last time is the target for Viagra. The target for ketamine is a ligand-activated channel, specifically the NMDA glutamate receptor, and we have learned all about NMDA glutamate receptors. They are calcium permeable, and also they serve in memory and learning. They are the ones that get plugged up by magnesium. So ketamine seems to enter and plug those NMDA receptors very much very similar to the way that magnesium enters and plugs them. Let's take some time out and have the promised and threatened quiz. Close book, close notes, close laptop, and so we replace the mouse gene with the altered gene, and because the gene produces a gene product that glows, we can easily figure out which mice have that altered gene. We select the mouse with the altered gene. We read many identical mice with the altered gene, and then we measure the drug response in the wild type mouse with the intact gene versus the altered mouse with the substituted gene or with the knocked out gene, and we do it in such a way that when we read them, we make them homozygous for the knockout. That is, we typically knock out both copies of the gene. You've learned all this in previous courses. So let's look at the results for knockout mice in neuropharmacology, and we're going to be discussing mostly behavioral observations. So the mu-opioid receptor knockouts, KOs, meaning knockout, they do in fact specifically lack responses to certain types of pain, and I'll show you how those experiments go on the next slide. So that really does give us proof that the mu-opioid receptor is necessary for the pain-killing responses of the opioids, morphine, and heroin. When we knock out the alpha-4, beta-2 nicotinic receptor, either by knocking out the alpha-4 or the beta-2 subunit, animals respond less to nicotine in pain tests. Nicotine is an analgesic, it suppresses pain, and they have less of a response to nicotine. And also they fail to self-administer nicotine for pleasurable drugs, as we will learn in by 155. Self-administration is a very handy and robust way of figuring out which drugs work and how much. Now when we knock out the dopamine transporter, dopamine transporter knockout mice are hyperactive. They show less of a response to cocaine, and they self-administer cocaine less. So it does look as though the dopamine transporter is a major target, but not the only target for cocaine. Now when we knock out cannabinoid receptors, these are GPCRs, they actually have very few obvious differences to normal mice. However, they don't show these rather subtle effects of THC or of anandamide. And THC and anandamide do produce decreased pain responses. The knockout mice don't have those responses. And THC and anandamide also decrease heart rate and knockouts do not have that response. Do the knockout mice get the munchies when you give them THC? I don't think that experiments have been done. Okay, on the other hand, some experiments just don't work. For instance, when you knock out NMDA receptors, the animals die at birth. So that's an uninformative result that tells us that NMDA receptors are necessary for postnatal life. It is possible to make conditional knockouts to knockout NMDA receptors after birth or in particular part of the brain, and very interesting neuroscience has come from those studies. So I promised to tell you about a couple of these assays. First of all, the pain assay. First of all, I should say that no permanent harm is done to the mouse. These experiments are carefully regulated. The experiment replaces the mouse on a hot plate at 55 degrees C. And one notes the time it takes for the mice to show signs of discomfort such as licking paws or jumping. We terminate the experiment at 30 seconds, regardless of the outcome. And a pain relieving drug increases the time to react. Typically, it takes just a few seconds. The pain reliever may increase the time, but we always terminate the experiment at 30 seconds. Carefully regulated, highly useful. Then another way of looking at the effects of a pleasurable drug is self-administration. So here we train the rodent, in this case a rat, to press a lever. We cannulate, we put a cannula in the rodent so that each time the animal presses the lever, a motor pushes the syringe forward in a drug syringe and the animal gets a little squirt of that pleasurable drug. And clearly it is possible to use an experiment like this to find out which receptors are involved, how much drug you need, whether the animal prefers one type of drug or another, whether pretreatment with one or another drug makes a difference, and where in the body the drug is acting by use of conditional knockouts. Now, one of the more complicated mechanisms for drugs involves MDMA, which is ecstasy, or amphetamines, or a large number of newly synthesized drugs. Some of them are called bath salts, others come out of clandestine labs at a great rate. They all look like substituted amines, typically with benzoyl groups or with aromatic groups. So ecstasy, ecstasy, moly, they are all weak bases with a pH of 8.5, and so that means that they can all pass through membranes. You'll remember that I told you about three transporters involved with monoamine neurotransporters, an ATP-driven proton pump, proton coupled vesicular serotonin transporter, and serotonin transporter on the plasma membrane, and this serotonin transporter on the plasma membrane called appropriately enough SIRT, serotonin transporter, is the target for the SSRIs. So if we put MDMA in the external solution, because it has a weak, it has an uncharged membrane protonated form, it goes right through the plasma membrane, right through the vesicular membrane. Because secretory vesicles have a low pH, a high concentration of protons, the MDMA molecule gets protonated inside the vesicle. This protonated version of the drug is not passively membrane permanent. It would get stuck in the membrane, but it is a substrate for the vesicular transporter. So it leaves the vesicular, the vesicle, carrying with it the proton, and this dissipates the vesicle's pH store as rapidly as it can pump, and so this short circuits the pH gradient in the vesicle. And then the drug can also pass through the plasma membrane serotonin transporter, and it's in a high enough concentration in the cytoplasm because of being dumped from vesicular transporters, so that it passes out into the synaptic cleft as well. And so the cell releases either the drug itself or serotonin by reversing this proton gradient, and the result is a massive release of serotonin. Can we measure these topics? We can indeed, using various techniques, one of them is simply enough electricity. And so here is an electrode that's modified, so it's connected to a patch clamp and can pass very small currents, but we can monitor dopamine, for instance, in the synaptic cleft, because you can oxidize these catechol groups to become ketones, and this current from oxidizing the hydroxyl groups passes through the carbon fiber. So if we release dopamine near a cell, we can detect that dopamine with an electrical means. And so here is an experiment from several years ago using dopamine transporter called DAT, knockout mice. So in the wild type mice, which are positive for the dopamine transporter, we stimulate the presynaptic nerve, and we get nice release of dopamine measured by the electrodes. And this happens again, we get lots of nice release. Now if we add amphetamines, we gradually deplete the vesicle store, but at the same time, and so we get less and less dopamine released, but also the amphetamine is releasing dopamine by itself near the synapse, and so the result is that we get a high concentration of dopamine near the synapse, and this will be stimulating GPCRs. If we do this experiment in a DAT knockout mice, we get less release in the first place because we can't fill the vesicles very well. If we blow up this trace, we notice that in the wild type mice, we have a nice brief one second transient measurement for the DAT, but in the knockout mice, the DAT gets released and then hangs around for a long time. Less of it is released, but we get a much prolonged release because we cannot take the dopamine back up into the presynaptic nerve because there's no dopamine transporter to do that. And ultimately in the DAT knockout mice, we get less and less dopamine released, but it doesn't build up in the synaptic cleft. There's not much of it around, and so the baseline stays. So this is an example of the way we can parse out the actions of the transporter of the drug target, in this case amphetamine, using either knockout mice or the drug. Let's talk about routes into the body for all of these drugs. So recreational drugs can be eaten or drank. They can be inhaled, smoked, or injected. And there are various routes depending on the drug. People take morphine and heroin by eating it. Very important use in pain control, especially for terminal patients. And of course morphine can also be smoked or injected. THC can make brownies. People don't usually snort THC, but they certainly do smoke it. And there's very little use for injected drug. If you can get away without an injected drug, you get away without injecting it, of course. Nicotine, well, your average major leach pitcher, choose tobacco, can be inhaled. And there are nicotine inhalers on the market which allow one to inhale nicotine without the tobacco smoke. And whether vaping is inhaling or smoking is a lively question. I would call it inhaling because you're not actually burning anything. Cocaine can be inhaled or smoked or injected. Amphetamines can enter the body in any of a number of ways. And of course speed gets injected. Speed is amphetamine. Ethanol really the only effective way to enter the body is by eating or drinking. Although there are some cases as I'll show you later where it can be injected. And civilizations have gone to great lengths with fermentation to produce drinks that taste good when they deliver ethanol. LSD really the only way that people take it is by eating it. Caffeine, again, caffeinated drinks are a very effective way. People don't inhale or smoke it. Under some circumstances for diagnostic purposes, it can be injected. And ketamine is actually quite membrane permeant. And so one can eat or drink ketamine. There are clinical trials underway with ketamine inhalers. Not for hallucinogenic use, but as an antidepressant. And I'll talk about that in later lectures. People talk about smoking ketamine or putting it in the cartridge of an electronic cigarette. And it can also be injected. And it is very handy to inject ketamine for animal experiments where it is a very useful anesthetic. Let's talk about the concentrations at which drugs act. Most of them act at concentrations of less than 10 micromolar. They are quite potent. And this is one reason they are used commonly. And it's one selective advantage that one doesn't need to eat or chew much of the leaves in order to get the aversive effect. As usual, ethanol is an outlier. And it's possible to calculate that the legal limit of ethanol in the blood, which is one and a quarter percent or one and a half percent is actually on the order of 20 millimolar. So it's enormously less potent than the other drugs. But because it's so soluble and common, it's easy to get a high concentration in the bloodstream. Any questions? Where in the brain are the actions? Well, in general, we talk about the dopamine energy system. We don't we don't actually use Nestler in this course. So let me... Well, you'll see it in a minute, actually. The dopamine system, you remember, I've talked to you about the handlebar moustache. The handlebars are the substantia nigra. The upper lip is the ventral tegmental area. And in this case, we've taken a sagittal section of the human brain right through the upper lip area like this. And so we see the ventral tegmental area, which projects to the nucleus accumbens. So these are the key parts of the dopamine ergic reward or pleasure or well-being system, activating the dopamine neurons in the ventral tegmental area, the upper lip, which then project to the nucleus accumbens. Accumbens means literally lying down, so it looks like a long, narrow nucleus recumbent. So that's the dopamine system. Then there are other aspects of the dopamine system that project widely in the forebrain. And presumably the actions of the ADD drugs are mostly on the forebrain and mostly deal with activating neurons and with helping people to remember. There's obviously an interesting paradox here that you give a cocaine-like drug, such as an amphetamine or Adderall, to a hyperactive person. Whereas I've told you that cocaine actually produces itself hyperactivity. And so the psychiatrists, bless their hearts, simply say that the action of an ADD drug in the brain of an ADD patient is paradoxical. That is, they don't understand why it calms down ADHD patients, but it does. There is the neuroadrenaline system. And actually there are very few cells in the brain that make neuroadrenaline, even in humans. So here's the full reference to Nestler. The region of the brain that makes neuroadrenaline is called the locus ceruleus. Cerulean is blue, like the sky. And so the locus ceruleus in some stains turns blue. It projects to many areas of the brain as does dopamine. So if we talk about system level actions, we could call the dopamine system the pleasure system. And it's activated by several recreational drugs. In fact, by most recreational drugs seem to produce dopamine and give a sense of well-being or pleasure. On the other hand, activating the neuroadrenaline system is more like giving a shot of adrenaline, flight or flight response. So we call it the readiness system. It's activated by nicotine, by cocaine, by amphetamine, and by caffeine. The perception association system is strongly activated by LSD and by ketamine and by THC. We think of these drugs as dissociative or producing mild hallucinations. And so in ways that we don't understand they're acting on the perception associated system. If we have a time, I'll give you a little more detail of that. And finally, then there are drugs that simply decrease neuronal activity. Morphine and heroin do this very well. And this is presumably how they stop pain. THC apparently does this as well because it's coupled to a GI-coupled receptor. Ethanol puts people to sleep. LSD, as I'm going to show you, does this as well. Ketamine does it too. So serotonin activates the serotonin system, which arises in the so-called rathae nuclei. And there are probably more neurons in the rathae nuclei than there are in the noradrenaline system. And they also project to many brain areas. And so this common theme among several recreational drugs is widespread projection, widespread action in the brain. So the overall action of recreational drugs, if we have to point to one of those overall actions, is that morphine and heroin are definitely inhibitory. So are THC and ethanol. The overall action of nicotine is certainly more excitatory of cocaine and amphetamine and of caffeine. And then there are drugs that essentially produce hallucinations or dissociation. So that would be LSD and ketamine with the caveat that in lower doses ketamine is also an antidepressant. So let's do a little bit of a literature search. Let's look at fMRI measurements, sorry, a literature club, a journal club, on a hallucinogenic serotonin 5-HT2A agonist in human brain. So this is the same system, although it comes from mushrooms that LSD might be acting on. And psilocybin gets metabolized to psilocin, which is the active ingredient of psilocybin. It looks a little bit like serotonin. It's got this amine, it's got the 5-hydroxy group, but it's got a modification, a hydroxyl group here. Sorry, the 5, yeah, the amino group. So these are subjective responses from subjects. So my surroundings change, geometric patterns, things look strange, sense of size or space. In other words, how do you quantify or how do you report on taking a trip? These are the ways they report. And the experiment is done with psilocybin itself, an injection, or with a placebo. And naturally the subject doesn't know which he's getting. This experiment was done in an fMRI machine in London, in a scanner. And clearly the psilocybin had effects. The subject was blinded to what he got, the experimenters may or may not have been blinded. So, clearly reported effects. So the surprising, and there are effects, changes in blood flow after psilocybin versus after the placebo. One of the more interesting aspects of this experiment is that actually these effects are all negative. That is, activity was reduced in the brain areas involved. And so if we look carefully at the data, the reduction clearly occurred in the thalamus, in the anterior cingulate, and in the posterior cingulate. In other words, in a number of brain areas, actually the most active regions before psilocybin became least active during the drug. So here is an effect that is opposite to what one would have expected. And so in neuroscience we say, ah, well we must have activated inhibitory systems. So it is suggested then that psilocin, the active metabolite of psilocybin, activates some GABA neurons via 5-HT2A receptors on those GABA-ergic neurons. And decreases overall activity of the more numerous glutamatergic neurons. How this leads to taking a trip, we don't know. So legal status of recreational drugs. This changes quickly. There are recreational uses, there are prescription uses, and there are non-prescription or over-the-counter uses. So morphine and heroin for recreational use are illegal. For prescription use, they are very, very useful. The DEA puts them under Schedule 2, meaning purely heavily regulated but available. And then over-the-counter use, actually, there are analogs, which have weaker actions, in cough medicines and in diarrhea medicines. THC for recreational use is legal in Colorado and in Washington. The person needs to be over 21. And it's taxed, brilliant government idea. For prescription use, something like 20 states allow THC, including California, it too is taxed. Nicotine is taxed for recreational use, no sales to minors. Nicotine is used for smoking cessation by prescription or over-the-counter in nicotine gums or lozenges, patches, or an inhaler. Of course, in recreational use, people also vape it with electronic nicotine delivery systems. Cocaine is simply illegal for recreational use. There are limited prescription uses, actually, for ear, nose, and throat surgery. There's no over-the-counter way to get cocaine. Amphetamine and derivatives are illegal for recreational use. For ADD and ADHD, they are scheduled to, you get them with a prescription, also used for narcolepsy. Again, this paradoxical effect that in some people, amphetamines wake people up, in others, it puts them to sleep. Diet pills have weaker amphetamines in them. Ethanol for recreational use is quite common, good source of taxes, not available for minors. In prescription use, in rare cases, for detoxifying a patient who's taken methanol or ethylene glycol. LSD is just plain illegal, no known uses, can't get it over-the-counter. Caffeine is quite legal, it is present in some migraine medications, and it is also present over-the-counter in some anti-histamine, anti-allergy pills. Ketamine is illegal for recreational use. For prescription use, it is schedule three, it is lightly allowed. And the major non-prescription use, if a patient, if a person can get hold of it, is for dissociative effect, although there are clinical trials now underway for ketamine as an antidepressant. As you may know, this is a research interest of my lab, and Alice Sue, who's here as a student, is working on trying to detect ketamine in brains. Some pharmaceutical companies allow off-label use, but they cannot advertise the on-label use of any drug, and physicians can prescribe a drug that is approved for some uses, for other uses, according to traditional standards of care. Okay, that's the story about recreational drugs. I need to go to a nicotine meeting this afternoon. Now, the question arises, what changes occur in the brain during chronic repeated exposure to an addictive drug? Well, I've given you only the first step in that very interesting question, and if you want to go further, you can take by 1.55 next winter. Sharon.