Discussions that mention morphine

Addiction & Recovery board


That explanation about dopamine is, I believe, more accurate with "upper" drugs such as cocaine, methamphetamine, ritalin, etc. opiates are a little different. In addition, it was a little simplified. I will do my best to explain.

The receptor concept introduced in the former post is the heart of the problem. There are special neurons concentrated in certain parts of your brain, spinal cord, and intestines that have on them what are called opiate receptors. There are several classes of opiate receptors, including mu, nu, etc. The neurons that have the special opiate receptors on them are the ones that control your breathing, pain reception, the muscles of your gut (which is why there is the effect of constipation), and a whole host of other things. These opiate receptors in these special locations are activated by natural opiate-like compounds produced by your body. These natural opiate-like compounds are known as enkephalins or endorphins.

You can kind of think of the receptor as a little gate in the wall of the cell, but it is slightly more complicated than that. Naturally, the natural enkephalins and endorphins in your brain bind to these receptors and "activate" them, which sends a cascade of signals to the neurons they activate, and the neurons with the receptors to which enkephalins and endorphins bind - as i have mentioned - regulate breathing, pleasure, pain. It is by binding to these receptors and activating the associated neurons that opiate drugs produce their effects.

Narcotic drugs also bind to these receptors, and actually bind more readily to the receptors than your bodies natural opiates (the enkephalins and endorphins)! By taking narcotics, these receptors in their specific brain areas become hyper-stimulated. The drug activates these receptors repeatedly and very powerfully, and because of this an interesting effect called "down regulation" happens. I will try to illustrate this with a simple text diagram. If this --| is the wall of your neuron (the dashes represent the inside, and the verticle line is the wall), and these { are the receptors:
A normal neuron will look like this, in this very oversimplified and mostly conceptual diagram. As you can see, the receptors are sticking out of the cell and are ready to bind with enkephalins, endorphins, or narcotic drugs that might float up to them:
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When you overstimulate the receptors with narcotics over a reasonable period of time, they attempt to normalize (counteract the overactivity) by downregulation:

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As this picture illustrates, your receptors become less sensitive to the drug and to your natural opiates by, in a way, "receeding" into the cell, and this is the reason it takes more and more and more of the drug to produce the same effect. Remember, if you want to be technical, this is a VERY oversimplified drawing and description, and the actual process is far more complicated.

That's not all! There are additional problems that lead to withdrawal, and this is the kicker! Because the narcotic drugs have a higher affinity for the receptors, and bind to them more readily, your bodies natural endorphins and enkephalins no longer have any effect. Your body begins to rely on the drug that you are taking, be it morphine, oxycodone, heroin, or whatever, to perform the functions that your natural enkephalins used to. Your body stops producing the enkephalins and endorphins, and becomes totally dependent on the drug to be normal! This is a very important reason that when you stop taking narcotics suddenly, you experience withdrawal symptoms! It takes a good amount of time once you have stopped taking the narcotics for your body to once again begin producing its own natural opiates, and this can be a painful time. In addition, your neurons have to recover from the down-regulation, which is completely reversible, but also takes time.

To clarify a little more - i think a previous post said that taking the drug actually makes your neurons produce more receptors. This is not true. It is the down-regulation of the receptors that makes it harder for them to be activated, and thus leads to the necessity to take more drug to obtain the same effects.

sorry for the lengthy post - Hope this info is useful!

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