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Q from USMLE CD

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Baobab
Forum Junior

Topics: 5
Posts: 17

02/04/07 - 02:00 PM

I got this Q from USMLE CD, (so the answer is there as well) but I just don't get it. Could anybody explain this somehow?? Thanks

Attached Files:
Symp Denervation.jpg (59 KB, 62 downloads)

Ancylostoma
Forum Guru

Topics: 42
Posts: 637

02/04/07 - 03:09 PM

I believe this is it, tyramine is a substrate that creates more norepinephrine within nerve synapse. This is why we dont eat tyramine comtaining foods with monoamine oxidase inhibitors(sypathetic crises). Epinephrine is able to ellicit is effects via the blood and thus causes vasodilation. Correct me if I'm wrong guys

You should go and look up how tyramine containing Foods are converted into NE, I think its would be talked about in your pharm book when they discuss monoamine oxidase inh.

Let me know what you find

Edited by Ancylostoma on 02/04/07 - 03:45 PM

Baobab
Forum Junior

Topics: 5
Posts: 17

02/04/07 - 03:28 PM

Thank you Ancylostoma for your input. I've looked at Goodman? pharm and got this diagram for Tyramine to NE to Epi pathway.

I never thought of the sites of action of Epi (in blood) and NE (in nerve synapse), but it certainly makes sense!! So is it that only the nerve is non-conducting for NE which is mediated by Tyramine, but still receive Epinephrine stimuli from blood?

I never even had a clue where to look at (I literally spent hours trying to figure out this Q) or what concept they were trying to test me on. You are a star!

Attached Files:
Tyramine to NE to Epi.jpg (51 KB, 24 downloads)

Clozapine
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Topics: 15
Posts: 164

02/04/07 - 03:45 PM

It`s straight from the kaplan pharma autonomic drugs: eye and CVS , donno which edition u r using though.

Classic example of why denervated tissue don respond to indirect agonists.

Tyramin release NE from the synaptic vesicles and cause increased SANS response, whaich obviously can`t happen in case of denervated tissue. If u use direct agonist,it works since the receptors are there and sometimes show increased response (due to receptor upregulation I guess)

Clozapine
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Topics: 15
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02/04/07 - 03:49 PM

Correction: from the mobile pool, not from the synaptic vesicles, whatever .... as long as its an indirect agonist

Ancylostoma
Forum Guru

Topics: 42
Posts: 637

02/04/07 - 03:52 PM

Lol your right, it is in kaplan just checked, the stupid questions dont have answers next to them though, Probably why I never did this section.

Edited by Ancylostoma on 02/04/07 - 07:09 PM

Clozapine
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Topics: 15
Posts: 164

02/04/07 - 04:06 PM

yup ... I guess I remember it b/c it took me FOREVER to solve it and then I saw they have it at the end of the Q/As rolling eyes

totally agree with Baobab though wink

good luck

Baobab
Forum Junior

Topics: 5
Posts: 17

02/06/07 - 10:14 AM

Thank you so much Clozapine (this was... alpha 2 agonist??) & Ancylostoma - you guys made it so clear!

Ancylostoma
Forum Guru

Topics: 42
Posts: 637

02/06/07 - 10:29 AM

a2 receptors inhibit norepinephrine secretion and have no place in this action. Dilation of pupil is by a1 receptor.

Revenged
Forum Newbie

Topics: 2
Posts: 16

02/06/07 - 03:13 PM

#10

Baobab wrote:
Thank you so much Clozapine (this was... alpha 2 agonist??) & Ancylostoma - you guys made it so clear!

Clozapine is an atpical neuroleptic (anti-psychotic drug)...

Perhaps you are getting mixed up with another drug... It's action is thought to be due to blockade of serotonin receptors (e.g. 5-HT2A receptor)

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