Friday Weird Science's Fightin' Fish: Is an antidepressant making your grumpy guppies zen?

Jun 10 2011 Published by under Friday Weird Science, Uncategorized

I thought of making this a normal science, but really it's just too weird for that.

I mean, what happens when you combine this:


and this?

(Source) far, probably nothing. But wouldn't it be fun to watch them fight...

Holmberg et al. "Does waterborne citalopram affect the aggressive and sexual behaviour of
rainbow trout and guppy?" Journal of Hazardous Materials, 2011.

As you've probably heard in the news for a while, Americans take a LOT of drugs. A LOT. I'm not talking cocaine or marijuana (though there's certainly a good bit of that), I'm talking prescription drugs. Anything from Adderall to Zoloft and everything in between. Most people used to think that when we took these drugs, we absorbed them and...that was that. And in a way, it is. For a time. But what goes in must come out. While some of what goes into us comes out as energy and heat and numerous other things, the drugs we take must end up being excreted, and that means coming out in the form of pee or poo.

And if you live in the US, that usually means that what comes out of you ends up in the water supply. Obviously you excrete pretty tiny concentrations of the drugs you take (you break down most of it), but there are millions of people in the US, and a good number of them are on (and therefore peeing) prescription drugs. While some of these get broken down into inert substances, a lot of them do not, and sewage treatment plants can really only do so much. The water, and the drugs in it, heads out to the rivers and streams, where it runs

Fish are similar to humans in many ways. In particular they have the same type of serotonin system that we do, complete with the same serotonin transporters. Serotonin is a chemical released from one neuron to another for communication. When it is released into the space between neurons (called the synapse), serotonin binds to receptors on the other side, which passes the signal along. This means serotonin doesn't even go INSIDE the other neuron. Instead, it stays in the gap between. But as you don't want serotonin all clogging up your receptors all day, it needs to get recycled. So we (and fish) have serotonin transporters, which suck serotonin back into the neuron, for either trash or storage.

And serotonin transporters are particularly important because of the drugs we have that target them. In particular, the selective serotonin reuptake inhibitor (SSRI) antidepressants, such as Prozac, Lexapro, Celexa, Citralopram, Zoloft, etc. These drugs prevent the serotonin from getting recycled, making it stay in the synapse longer. While low levels of serotonin itself don't cause depression, scientists currently think that increasing serotonin in the synapse by blocking the transporter may lead down the road to the birth of new neurons in some brain areas, which may relieve depressive symptoms (or it may be something else, this whole thing still needs a lot of research).

So that's all good for us. But what about fish? Fish don't exactly get depressed (that we can tell, anyway), but serotonin does play a role in their behavior. In particular, low levels of serotonin in fish can promote aggression, which can in turn affect their mating behavior.

So antidepressants increase serotonin, serotonin affects aggression in fish...are the antidepressants in the water affecting how the fish behave? Are we transforming grumpy angry fish into zen, peaceful fish?

To find this out, the authors took a bunch of farmed rainbow trout, and made them fight.

(Ok, not like this, but I love the comparing mouth size bit. Hehehehe)

But male trout DO fight, and they did test them off against each other (though whether they bet on the outcome is a different question). They also tested the aggression of the fish using a mirror test, where they put a mirror in the tank. The male fish thinks it's another fine looking, handsome male fish, and gets suitably grumpy that this guy is stealing his spot style. He will display and even attack the mirror.

They also tested the sexual behavior of the fish (after all, many SSRIs cause sexual behavior problems in humans), by putting the male trout in with some winsome females, and seeing how many times the male thrust his goands at them (aww, it's just like in humans!).

So now we have all of these tests...and then they put citalopram in the water. Citalopram is an SSRI antidepressant sold under that name, and others as well, such as Celexa and Lexapro. In this case, they took a dose that has been commonly seen in wastewater and put both adult trout and small fry into it for 3-7 days. Then they tested them for aggression and sexual behavior.

And...well, it didn't show anything. None of the tests showed anything. They looked in fry and in adults, and aggressive behaviors and sexual behaviors were basically unchanged. So...looks like trout aren't very sensitive to antidepressants. The authors hypothesize that this because the drug can't get into the fish very well.

That may be, but I'm not sure. After all, scientists have given oral dosing of drugs to other fish before and gotten significant effects. My thought is that the exposure is probably too short, 3-7 days isn't very long, even for a fish. It's also possible that the doses used are just too low. But I'd also be really interested to see what happened if they gave citalopram to the fry the whole time they were growing up. After all, this citalopram in the water isn't going away. Does it have effects when they are adults? Not only that, citalopram is just one of the antidepressants found in water that's been through human hands, could a combination of drugs produce a stronger effect? Of course there are more behaviors out there than just aggression, what about other behaviors? And finally, there's always the possibility that citalopram in fish really does...nothing.

But in the meantime, if you eat a trout, don't worry, the antidepressant levels in there are probably low. And since they didn't affect his aggression, you can probably convince yourself that he was a real fighter in life.

Holmberg, A., Fogel, J., Albertsson, E., Fick, J., Brown, J., Paxéus, N., Förlin, L., Johnsson, J., & Larsson, D. (2011). Does waterborne citalopram affect the aggressive and sexual behaviour of rainbow trout and guppy? Journal of Hazardous Materials, 187 (1-3), 596-599 DOI: 10.1016/j.jhazmat.2011.01.055

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