Heroin and endorphin? AAMC The Official MCAT Practice Question section3 Q #14

[m25]

Why is the answer B? I thought the answer was A because heroin increases endorphin and naloxone blocks the effect of endorphin so injecting naloxone should reduce the effect o heroin...?
Note: Naloxone is a chemical that binds to the endorphin receptors and blocks their functioning, as given in the passage.

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[Holmwood]

You're not allowed to post questions like this, I believe.

 

[m25]

You're not allowed to post questions like this, I believe.

According to the rule thread, it seems like it's allowed as long as I make it clear in the title that it is from AAMC.

 

[RH8448]

Naloxone, according to the passage, is a endorphin antagonist. This question does seem counterintuitive at first. Instead of seeing two different drugs, see the two drugs as doing the same thing.

ABA (endorphin addicted) rats stopped using heroine because they were addicted to endorphins. If a heroine addicted rat was injected with a drug (naloxone) that made it impossible to experience endorphins, that rat would be even less likely to exercise, thus, worsening his addiction - or increasing the effects/desire for heroine.

 

[Blueprint MCAT Tutor]

If a heroine addicted rat was injected with a drug (naloxone) that made it impossible to experience endorphins, that rat would be even less likely to exercise, thus, worsening his addiction - or increasing the effects/desire for heroine.

This basically gets it. The rats wanna feel good. They're addicted to feeling good. Naloxone blocks endorphins and makes them feel bad. So now they super-duper wanna feel good so they really REALLY want that sweet, sweet heroin.

 

[whatwhy]

This basically gets it. The rats wanna feel good. They're addicted to feeling good. Naloxone blocks endorphins and makes them feel bad. So now they super-duper wanna feel good so they really REALLY want that sweet, sweet heroin.

I'm really confused about this question. On this website, it specifically states the answer is A, not B. So which is right? I can buy either theory, but to me it makes more sense that if you're a heroin addict and someone keeps injecting you with naloxone, you will eventually come to realize that the heroin wont do anything for you. I guess short term maybe you'll want more, but long term you wont want it anymore. Hmm...

 

[RyanLJ]

What is depicted in figure 2? It's mentioned, but not included, in the linked website.

I'm wondering if there's anything that would help infer that Naloxone is a competitive inhibitor, and thus can be overcome by increasing endorphin concentration sufficiently - and likely in turn, by increasing heroin dosage.

 

[nomdeplume1234]

Does the passage state the function/effect of Heroin or is this supposed to be outside knowledge? Because if not I can see why someone would think there was a link between Heroin and endorphins thus making choice A look like the right answer. But if I went into the test knowing that heroin was only similar to endorphins then I could reason that Nalaxone would inhibit the endorphine but no the Heroin and so the rat would want the Heroin to get the same feeling that endorphins produced.

 

[Godspeedyou]

I would be interested in hearing the official answer to this question since I was a psych major lol. Since Naloxone is an antagonist, it precipitates withdrawal symptoms, which are opposite to the primary effects of heroin. If B is the correct answer, then the rats would associate pain, fever, seizures, etc. with Naloxone and they would associate the reduction of pain, a rush, and euphoria, with heroin. That's how I see it at least.