Why Do Opioid Receptors Exist in the Gut?

[daddysgone]

So I was thinking about opioid receptors and the fact that they exist in the gut, and am now wondering what purpose they serve there.

Obviously I know HOW they work and that when opioids bind to these receptors peristalsis is greatly reduced (thus causing constipation), but I cannot think of a reason for why we would have evolved to have these receptors in our gut, and what purpose they serve.

The only thing I can think of is that when we experience pain and our bodies produce endorphins, these endorphins bind to the receptors in our gut- but why would it be advantageous for peristalsis to slow when we are in pain?

Perhaps I am missing something very obvious. Anyone have any ideas?

 

[NeighborhoodThreat]

damn good question.

 

[sekio]

Why do we have serotonin and dopamine receptors in the brain (and so many serotonin receptors in the gut)? Why do we have ion channels all over our cells? What jackass let our eyeballs be built completely backwards and upside down?

 

[pofacedhoe]

fear (adrenaline) makes you shit yourself which may not be helpfull if you are wounded

 

[daddysgone]

Why do we have serotonin and dopamine receptors in the brain (and so many serotonin receptors in the gut)? Why do we have ion channels all over our cells? What jackass let our eyeballs be built completely backwards and upside down?

I get your point....but I was hoping for more of an answer to the question as opposed to a bunch of other examples of oddly located receptor sites.

 

[nuke]

I'm pretty sure the answer is in economy and evolutionary convenience.

Let's say you're an organism that is multicellular and initially you make sodium ion channels to reaction to some sort of stimuli, let's say light.

Fast forward a few million years. Now you've developed ground motility with little leggy appendages. You already made these neat, highly responsive ion channels to handle your response to light; why not make this appendage muscle tissue that you've differentiated, which is far away from the light detection part of your body, use these same sorts of receptors to trigger muscle movement through your nervous system? Surely there isn't a big consequence if the cell types are far apart and sodium flux in the muscles cannot trigger responses in the eye part of your body.

And so, in the interest of not having to make a new receptor type as well as endogenous ligands for each new thing you want your organism to do, you just make the cells become isolated and differentiated and reuse the same signalling systems. This is why the vast majority of cell signalling is conserved in all different sorts of cell lines, even if they do different things in different places.

 

[23536]

smooth muscle regulation

they're not only present in the gut: they're present throughout vascular smooth muscle

also (just speculation on my part): they may be less likely to be triggered by the heterogenous mix of substances and nutrients being absorbed