Transcript

Snail heart research with Michelle Gibson

Michelle GibsonMichell Gibson
m.gibson@latrobe.edu.au

Matt Smith:

You're listening to the La Trobe University Podcasts. I'll be your host, Matt Smith, and I'm here with Dr. Michelle Gibson from the Department of Pharmacy and Applied Science. How are you doing today, Michelle?

Michelle Gibson:

I'm very well. Thanks, Matt.

Matt Smith:

You're doing research with snail hearts, dissection. Not just snails, actually, with rats as well, to study the effects of serotonin. Is that right?

Michelle Gibson:

That is correct, yes.

Matt Smith:

And why are you doing that? Why are you studying the effects of serotonin on snails and rats?

Michelle Gibson:

OK. Serotonin is actually a very important medicine in our community. It's used in appetite suppressant tablets and it's also used for anti-anxiety disorders and anti-depression. A few years ago, in the medical community, we became aware that serotonin was actually causing heart disease in some patients. In our quest to find out why that was the case, many scientists have been using different approaches. From my background as a zoologist, I was aware that snails use serotonin in their hearts naturally, and I thought they might represent an interesting positive control model to use and see how serotonin worked normally and then perhaps look at a mammalian model like the rat and see how it might cause disease.

Matt Smith:

So, how does serotonin affect the snail's heart? Not very much at all, by the sound of it.

Michelle Gibson:

It increases heart rate. It increases the strength of contraction, much like adrenalin does in our hearts. And so, that's a normal mechanism for the snail. And so, when you do add serotonin to different concentrations in snail hearts, you'll see an increase in force up to a maximum and an increase in heart rate right up to a maximum.

Matt Smith:

And how about on the rat's heart? How would it affect that?

Michelle Gibson:

You see small changes in the rat heart in the work we've done, so far. You do see some slight increase in tension and a slight increase in the heart rate, particularly in the atrium of the heart.

Matt Smith:

So, would the objective be to find out what the difference is between the coping mechanism of the snail heart and maybe the human heart?

Michelle Gibson:

Absolutely. You want to look at what the properties are in a mammalian organism like the rat, which mimics the human condition, and see what sort of changes you get to serotonin there and compare that with a more physiological mechanism that you would see in snails, which is the normal process for the snail. By the differences in the response between the two tissues, hopefully we can pick up clues as to why it causes disease in humans.

Matt Smith:

Why did you choose snails? What is it about snails' hearts, in particular?

Michelle Gibson:

OK. Snails are an interesting choice, I agree. Being a zoologist, I have studied many animal species over the years. And one of the nice things about snails is they have a heart that spontaneously beats like ours does. And so, this means that many of the mechanisms inside their heart should be similar to what you would see in a human heart. It's also an easy choice. It's an easy animal to get and not difficult to keep. Not many people worry about you killing snails. I think most people stomp on them if they find them in the garden. But in terms of their physiology, they're probably not a bad choice.

Matt Smith:

Is their heart is similar to a human heart?

Michelle Gibson:

Quite similar. They only have one auricle and one ventricle, whereas we have two atria and two ventricles. But when you look inside the cells and you look at the mechanisms, how their heart is activated, they use similar hormones and similar neurotransmitters. They use calcium like we do. It's just that there are some small differences in the way they work. They're close enough that I think we can actually try and use it as a model.

Matt Smith:

And what point is your research at now?

Michelle Gibson:

Sure. We've been characterizing the properties of the snail heart for the last three years. We've done a lot of work looking at its response to adrenalin and nuero-adrenalin, which are the normal mechanisms of the human heart. We've investigated how serotonin works in their heart. When these drugs and these agents bond to heart muscle cells, they bind to specific receptors, to the binding sites. We've been characterizing some of the properties of those binding sites and we now know that you get the same types of binding sites in snails that you see in humans. So, there is a similar chemistry that goes on in the snail heart to what you would find in a human heart. So, this has confirmed that a model might be useful.

The other sort of work we do at the moment is looking at intracellular calcium, looking at the measurements of calcium inside the cells. Normally, as the calcium inside heart muscle cells increases, the force increases. This can be stimulated by drugs and agents like serotonin. So, at the moment we're using single cells that we isolate from the snail heart and from the rat heart, and we're putting these agents like serotonin onto the single cells and we're measuring the calcium concentration with a fluorescent probe, which emits light in the presence of calcium.

Matt Smith:

What is the end result that you're aiming for? What's going to be the outcome of all this research?

Michelle Gibson:

What we hope to do is better understand how serotonin works in the heart in both animals, the rat and the snail. But ultimately, we wanted to see what sort of mechanisms are involved in causing disease in humans and rats. Some researchers overseas suggested that serotonin might switch on genes in human heart cells that cause the heart to grow and that causes cardiac hypertrophy. We don't see that in snails but we might see that in rat hearts as well.

So, what we want to do is better understand the mechanisms to see whether or not we can understand why serotonin is doing what it is. And with that sort of information, hopefully that can get back to the pharmacy industry and medicinal chemistry that make drugs that they have to target the receptors better without the side effects of causing heart disease.

Matt Smith:

OK. Dr. Michelle Gibson, thank you for your time.

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