Addiction-brain effects: Sex addiction, neurotransmitters, and being love addicted

***A disclaimer: Sex addiction is a relatively new concept in science. I haven’t been able to find much research on the subject, so much of what is being said here is my interpretation of the current literature on sexual responsivity in humans.***

sexI’ve already mentioned that scientists are beginning to consider behavioral addictions (like gambling and sex) as being similar to drug addiction. We’ve also covered sex addiction on the site quite a few times.

Since we’d covered the addiction-brain effects of some of the major drugs’ (see here for opiates, crystal meth, and cocaine), I thought it’s time to write about the possible science behind sex addiction.

The sexual activity cycle

Scientists have divided human sexual interaction into 4 stages:

  1. Desire – Represents a person’s current level of interest in sex. It is characterized by sexual fantasies and a desire to have sex.
  2. Arousal – Includes a subjective sense of sexual pleasure accompanied by a physiological response in the form of genital vasocongestion, leading to penile erection in men and vulva/clitoral engorgement and vaginal lubrication in women.
  3. Orgasm – Involves both central processes in the brain and extensive peripheral effects. Orgasm is experienced by the peaking of sexual pleasure, release of sexual tension, rhythmic contraction of the perineal muscles and pelvic reproductive organs, and cardiovascular and respiratory changes.
  4. Resolution – The final stage of the normal sexual response cycle. There is a sense of release of tension, well being, and return of the body to its resting state.

After sexSex addicts don’t seem to have a problem with stage 3, and resolution is more like the end of sexual behavior. So we will focus the rest of our attention on the other stages 1 and 2.

Sex and neurotransmitters

While sex doesn’t involve the ingestion of substances, each of the above cycles does involve the release of many of the neurotransmitters we’ve already discussed (dopamine, serotonin, etc.).

In fact, there seem to be three major area in the brain that are activated during sex:

  1. The Medial Preoptic Area (MPOA) – This is one of the areas where all the sensory inputs to the brain converge. This. This area is crucial for the initiation of sexual response – the move from desire to arousal. It is mostly the release of dopamine within this area that supports sexual responding. Animals with lesions here can’t  mount or thrust.
  2. Paravantricular  (male) or ventromedial hypothalamus – These area are responsible for non-contact sexual responses. Dopamine is once again the main activating agent here.
  3. The mesolimbic system – Important for the motivation towards anything “good” this system is also very involved in motivation for sex, a big part of the desire and arousal stages. As with drugs, it is the release of dopamine with this system that increases the motivation for sex.

We haven’t discussed the first two area much, and from my understanding, their functioning is relatively specific to sexual response. However, we’ve certainly mentioned the mesolimbic system. This is the same system involved in the brain’s processing of opiates, cocaine, methamphetamine, and essentially all other drugs. It is also the system in charge of food motivation.

As you can see, dopamine is an activating neurotransmitter for sexual response. Serotonin on the other hand, plays an inhibitory role in sex. Through its activity on a number of brain area, serotonin reduces desire, arousal, as well as the ability to orgasm. The increase of overall brain-serotonin levels is one of the main reasons for reduced sexual responsivity in individuals who are taking SSRI antidepressants.

What about sex addiction?!

Aside from a few specific authors (like P. Carnes), scientists still find themselves struggling with whether or not behavioral addictions should be considered similar to drug and alcohol addiction or whether they are examples of compulsive, or impulsive, behaviors. I personally believe that these all share more common features than we may yet realize.

Nevertheless, for addicts, the subjective experience of a substance, or behavioral, addiction is similar. It is an inability  to control a behavior in the face of repeated negative consequences that is often accompanied by a need for more and a reduced sensitivity to the act.

Given my recent reading on the brain processes involved in normal human sexual response, I’ve developed my own early theory about sex addiction:

Given that many of the same neurotransmitters are involved in the regulation of sex, it is my belief that sexual addicts or those experiencing sexual compulsions, fall into one of two categories that probably overlap to some extent:

  1. Individuals who have reduced inhibitory capacity (like those with impulse control disorder, ADD, or ADHD for example). These individuals find themselves acting out relatively impulsive behaviors that others without such dysfunction seem to effortlessly control. Given what we know about impulse control disorders, it is no wonder that these individuals often find themselves engaging in more than one such behavior, including drug, sex, and other poossibly addictive activities.
  2. Those who’ve had sex paired with a strong neurological response – Given the important role of dopamine in all rewarding activities (what scientists call appetitive response), it is very possible that two or more rewarding experiences that are linked may increase the brain’s response to any of the individual rewards.

neurons that fire togetherLet me explain the last point: In neuroscience, there’s the concept that Neurons that fire together wire together,” which is to say that events that happen at the same time, if they are strong enough, may form their own neural networks. If something strongly negative (like violence) happens in conjunction with sex, the experience might lower sex responsivity. However, if a strongly rewarding event happens at the same time, the link might serve to enhance response for both future sexual experiences and the linked event.  The people in the first group are likely to often fall into this category due to their use of psychoactive substances. Drugs release huge amounts of dopamine, which may then become linked with sexual response, making sex seeking as strong as drug seeking.

So that’s my take, for now, on sex addiction. Like other addictions, it has to do with the exposure to a very rewarding event that in a subset of individuals ends up developing an exaggerated response or an inability to control it. Since feeling of love and intimacy can often be just as rewarding, people often refer to themselves as love addicted, and not sex addicted.

Sources:

1) A. G., Resnick, & M. H. Ithman (2008). The Human Sexual Response Cycle: Psychotropic Side Effects and Treatment Strategies. Psychiatric Annals, 38, pp. 267-280.

2) E. M. Hull, D. S. Lorrain, J. Du, L. Matuszewich, L. A. Lumley, S. K. Putnam, J. Moses (1999) Hormone-neurotransmitter interactions in the control of sexual behavior. Behavioral Brain Research, 105, 105-116.

Addiction brain effects : Opiate addiction – Heroin, oxycontin and more

Okay, we’ve talked about crystal meth and cocaine and how they affect the brain during drug use. As I mentioned, both cocaine and meth interfere with the way the brain stores and cleans up important neurotransmitters, including, most importantly, Dopamine and Norepinephrine.

opiates-morphine & heroinThe class of drugs known as opiates, which includes morphine, heroin, codeine, and all their derivatives (including oxycontin), acts on the brain in a completely different manner. Since our goal at All About Addiction is to explain drug use and abuse as comprehensively as possible, let’s turn our attention to this opiate addiction next.

Heroin, morphine, oxycontin, vicodin and other opiates

While cocaine and crystal meth work by disrupting the normal functioning of molecules responsible for cleaning up released neurotransmitters, opiates work by activating actual receptors that naturally occuring neurotransmitters activate. Substance like this are known as agonists; they perform the same action (identically as, to a lesser, or greater extent) as a substance the body already manufactures.

In the case of morphine, heroin, and most other opiates, the most important receptors activated are knownOpiate Receptors as µ-opioid receptors. Activation of the µ-opioid receptors is associated with analgesia (suppression of pain), sedation, and euphoria, which makes sense given the relaxing, pleasure inducing effects of opiates.

Natural opioids (also called endogenous opioids), which include endorphins, are used by the body to relieve pain and increase relaxation, especially during periods of extreme stress. These are the chemicals that make sure we can function during accidents, like after breaking our leg…

Opioids and dopamine

Opioids also increase the amount of dopamine in the brain indirectly. As I mentioned in the earlier posts, dopamine is thought to be the reward indicator in the brain. Unlike crystal meth and cocaine, heroin and its relatives increase the activity of dopamine neurons by releasing the hold that other neurons (that use GABA) have on them. Think of this as the release of pressure on a hose spraying water on a lawn. When the pipe is pinched, only so much water can get through, but once the clasp is released, water can flow in greater quantity; this is essentially what opiates do.

Heroin addiction and long term opiate use

Like I said before, this doesn’t sound so bad, does it? All we’re talking about here is the increasing of the functioning of system that already exists in the brain. The problem isn’t so much in the process, the problem starts when this system gets activated for long periods of time.

HeroinHeroin addicts, and other frequent users of opiates complain about the extreme discomfort they feel when they stop using the drugs. This discomfort has been described as the worse case of the flu you could imagine. Doesn’t sound too appealing, does it? In fact, withdrawal symptoms associated with stopping opiate use are at least one of the main reasons many users return to the drug after trying to clean up. This in addition to all the other effects of the drug on the brain to make wanting to stop so much harder.

The reason for the pains and aches? Given the overactivation of its pain suppression system, the body not only reduces its own supply of opioids, but it also turns up the sensitivity on its pain receptors. Heroin users notice this as an increase in tolerance, but they compensate for it by simply using more. However, when they stop, they’re left with a body unable to suppress its own, hyper sensitive pain system. The results are more than uncomfortable, they’re simply excruciating…

Another common complaint of addicts is diarrhea. This, again, is simply the reversal of the constipation caused earlier by heroin’s actions on opioid receptors that are present in the peripheral system (outside the central nervous system).

I’ve heard addicts speak online about the slow recovery from opiate addiction and I want to dispell a myth here:

Opiates DO NOT stay in your system for weeks or months – The drug itself is gone from the body within days. The reason for the continued suffering is the slow adjustment of your brain and body back to the way things were before the drugs. Think of how long the tolerance took to develop… Now play the tape back in reverse. That’s what happening to you. You can help relieve the pain, but know that if you use anything in the opiate family, you’re making the process last much longer…

So, in summary: As usual, the actions of opiates on the body and brain are not all the severe, extreme, or inappropriate. Opiates are still used in medicine for pain suppression, not only because they work, but because the potential for abuse when used in this way are minimal to non-existent. However, as with all drugs, continued, chronic, abusive use of opiates will change the way your body functions in ways that will produce the exact opposite effects of those users like so much. This leaves people not only with possible addiction problems, but also with a terrifyingly uncomfortable return back to normal functioning.

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The brain addiction connection : Crystal meth, and our friend dopamine

We’ve talked about the general way in which neurons in the brain communicate with one another and then reviewed the ways in which cocaine messes some of the basic processes that the brain depends on.

It’s time to move on to another drug, and since the brain-addiction connection is similar for meth and cocaine, it seems the natural next step…

Methamphetamine (speed, ice, glass, crystal, meth)

Remember how we said that cocaine affects the way that dopamine is cleaned up after being released? Well, crystal meth also affects dopamine, but in a different way:

Instead of not allowing a molecule (DAT) to pull released dopamine back into the cell that released it, methamphetamine doesn’t allow the dopamine in a cell to be stored in the little packets that it’s supposed to be put away in. Like the DAT molecule, there’s another molecule that packages dopamine (and other neurotransmitters actually).

This molecule is called vesicular monoamine transporter (VMAT) because it puts a specific kind of neurotransmitter (called monoamines) into packets called vesicles.

You may be asking this right about now:

“If cocaine and crystal meth act in such similar way, why are their effects so different?”

That’s a very good question.

Even though these two ways of affecting dopamine seem very similar, they cause different changes in the levels of dopamine in the brain:

This flood is similar to the effect of crystal meth on the brain. By interrupting the way the brain packages dopamine, speed causes an unstoppable flood of this neurotransmitter.While cocaine doesn’t allow the neurons to take dopamine back up (reuptake), the brain has these small monitoring devices called autoreceptors. These receptors detect the levels of dopamine in the brain and adjust the output. When cocaine increases dopamine levels, these autoreceptors decrease the amount of dopamine being released.

The problem with crystal meth is that the dopamine can’t be packaged at all, which means that whether the autoreceptors tell the brain to turn down dopamine output, the fact that the dopamine won’t go into it’s packages means it just keep leaking out.

Imagine having a burst pipe and trying to stop the flood by turning down the faucet… not too helpful, right?!

So what you end up with is a long lasting flood of dopamine that the brain can’t do much about… You may have already figured it out, but this is one of the many reasons why crysal meth has become the new drug epidemic; it just does its job really really well!

Dopamine function in a non-drug-using, meth addict after quitting, and a meth addict after 1 year of staying cleanThe long lasting effects on the brain are similar to those of cocaine, but can be even more devestating. Meth is very neurotoxic meaning that at high levels, it can actually kill neurons by over exciting them. In fact, for both cocaine and methamphetamine, but especially for meth, it can take a very long time (a year or more) for dopamine function to look like anything close to a non-user’s brain (look for the decrease in red in the middle figure showing less overall activity in this area).

Check out this video about meth’s effects:

The brain-addiction connection: Cocaine, dopamine, and more

Okay, so we’ve covered how the brain’s neurons communicate with one another normally; now let’s learn about how drugs mess things up to produce their specific effects. Since the brain-addiction relationship is different for different drugs, we’ll do this one by one, starting with cocaine:

Cocaine

One of the most commonly abused drugs, cocaine interrupts a molecule in the brain that’s responsible for clearing away the dopamine that is released during normal functioning (it’s called DAT). Like I’d said before, neurons talk to each other by releasing these neurotransmitter molecules to transmit impulses from one to another.

Imagine for a second that every time you spoke, the sound of your voice would continue on, reverberating endlessly. By the time each of us would be done uttering our first sentence, the world would be a mess of unintelligible sounds, echoing forever. This wouldn’t make for a very effective way of communicating.

Sound loses energy as it travels through air, eventually having so little energy that it no longer moves enough air to be audible. This keeps each word distinct and meaningful. In the brain, the individual messages between neurons are similarly kept distinct up by a number of processes.

These include dissipation, chemical breakdown, and reuptake.

Let’s learn more about these processes

Dissipation is a process similar to the story with air and sound, as the molecules move around, their concentration gets lower, and they become less likely to activate anything.

Chemical breakdown does is exactly what it sounds like, chemicals breaking the neurotransmitters down so they can no longer activate anything.

Reuptake is a more complicated process of recycling. Instead of letting all those precious chemicals go to waste, the brain recycles them so they can be used again later. Cocaine blocks the molecule that makes this reuptake process (for dopamine) possible. It’s a small molecule that carries the cocaine back into the cell that released it. Cocaine wedges itself in place of the dopamine (see picture below) and therefore deactivates it.

Dopamine Transport Molecule

What does cocaine’s action result in?

The result is that since it can’t be as efficiently cleaned up, dopamine ends up hanging around the brain for longer than it’s supposed to. Because dopamine is one of the brain’s main “pleasure”, or “positive” signaling molecules, users of cocaine feel better than they would otherwise as a result of this extra dopamine.

This doesn’t sound like such a bad thing, does it? Reuptake is a small price to pay for feeling a high that is almost “naturally produced” (some of the brain’s own dopamine hanging around for longer than it should). The problem is, that like in anything else, for every action, there’s a reaction…

What happens when cocaine in taken for a long time?

Faced with increasing amounts of dopamine, the brain starts adjusting in these ways:

  • It starts out by producing and releasing less dopamine, because as far as it’s concerned, the balance has been interrupted.
  • The number of receptors available to bind with dopamine is also reduced.
  • Next, it starts turning up brain systems that are supposed to counteract the actions of dopamine in order to once again, adjust for the increased levels.

Overall, these are some of the reasons for the “come down” or, after effects of a heavy night of cocaine use.

Over time, many of these changes become long lasting, resulting in a whole set of undesirable effects for the user, including withdrawal, mood problems, as well as some serious problems with thinking and control over behavior.

Not to be ignored are the effects that cocaine use, and the good feelings it initially brings along, have on motivation and normal reward functioning and learning in the brain; but we’ll get to that in another lesson…

Question of the day:
Does the above explanation of how cocaine works help you make sense of the effects it has? Could you see how these effects would possibly bring about addictive, rather than recreational, use?

The brain-addiction connection : Neurons and neurotransmitters

As I’d mentioned in an earlier post, while many people experiment with, or use, drugs at some point in their lives, only a small percentage (between 10%-15%) develop chronic drug abuse and dependence problems. While some of the specifics of what makes one person more likely to move from recreational use to addiction are still being investigated and hotly debated, we do know quite a lot about what happens in the brain when drug are used.

Before I can go into the specifics of the brain-addiction connection…

We need a little background on the way the brain works:

The neuron

The brain is in essence a very complex network of interconnected fibers (neurons) and their maintenance and support structures. The brain contains about 10,000,000,000,000 (10 trillion) of these cells, and they each make many connections.

The left end of the neuron in the picture on the right is called the dendrite; this is the neuron’s main information receiving hub. The long part extending to the right is called an axon, and it ends in axon terminals that eventually connect to other neurons’ dendrites.

This is the basic way in which everything that happens in the brain is communicated, including our thoughts, feelings, movements, and memories!!! Dendrite to axon, to axon terminals, to dendrites, and back to step 1. How this transmission is achieved within the neuron is not necessary for this discussion; let’s just say that you should eat your bananas and make sure you always have some potassium, sodium, and calcium in your body…

How do the neurons talk to one another?

Neurotransmitters

What is important for us is the way these neurons transfer information across the gap between the axon terminals and their connecting dendrites. This is achieved by chemicals called neurotransmitters. There are quite a few of these, but the main ones we’re going to be concerned with are serotonin, adrenaline, GABA, and dopamine as these are some of the major players in drug addiction (especially dopamine).

When a neuron wants to send a signal to its neighbor, it releases packets of a neurotransmitter (most axon terminals release only one specific neurotransmitter), and these are received by specialized receptors at the dendrites of the receiving neuron. If enough neurotransmitter is released and enough receptors are activated, the signal starts again and the cycle continues…

Neurotrasnmitters and drug use

Most abused drugs disrupt some combination of factors within this mechanism to produce both the intended, and unintended, effects they are known for.

Alright, that’s probably enough to absorb for now, more on what specific drugs do to interrupt this process soon!

Question:
How many of you knew about the ways in which drugs affect the brain? Would you mind sharing the things you’ve learned and where you’d learned them?

About addiction: Animal research, food addiction, policy, and cocaine addiction

Here are this weeks gems when it comes to learning about addiction. As usual, if you click this title’s post, you’ll get a list of our related post as a bonus!

Adventures in Ethics and Science A nice post about the current state of the animal-rights dialog

Addiction InboxMood Foods (and their possible role in food addiction)

Addiction TomorrowAdvocacy and Treatment

PhysOrgAltered reward-based brain-activation in cocaine addiction

About addiction: Prescription overdose, legalization, methadone, and the brain.

Here are this week’s must reads posts about addiction. Don’t forget to click the title for our related posts!

From the other allaboutaddiction (.net) Overdose deaths due to prescription medication

From Addiction InboxThe economics of drug legalization

From Addiction TomorrowA great balanced post about methadone

From PhysorgThe neurological consequences of early meth exposure

That’s it for this week. Enjoy!