“So what do you do?”…

We’ve all been there. Whether it’s at a family gathering, a friend-of-a-friend’s party or in the queue for the beer festival. At some point we’ve been asked by someone we vaguely know (or a complete stranger) “so what do you do?”.

Sometimes we’re waiting for it, as sooner or later the small talk will turn to what we do on a day-to-day basis. Sometimes the question is completely unexpected and results in a slightly blank expression as we’re trying to gather our thoughts.

I’m always ready to answer this question.

“So what do you do?” Well, the general area of my research is using cannabis to treat epilepsy.

Photo courtesy of Marcus Haag

Presenting my research in the form of a Science Slam. Photo courtesy of Marcus Haag

As you can probably imagine, people tend to latch on to the ‘cannabis’ part of that statement and I’ve found that I usually get two types of responses. I either get something like “Wow! That’s really cool” or “Hmm, ok”. To be honest, I’m not surprised that some people are sceptical about using an illicit drug to treat a disease – I certainly am! But the thing is, there’s so much more to it than simply giving cannabis to a person with epilepsy.

The cannabis plant contains around 500 chemicals. Of those ~500 chemicals, approximately 100 are unique to the plant and are known as cannabinoids. Of those ~100 cannabinoids, only 1 produces the euphoric effects associated with taking cannabis. This chemical is known as ‘delta-9-tetrahydrocannabinol’, or simply ‘THC’ for short. It’s described as being ‘psycho-active’ because it binds to, and activates, cannabinoid receptors that are expressed within the brain (CB1 receptors).

What about the other 100 or so cannabinoids found in the plant? Well, some of these have been studied in a variety of disease states including cancer, diabetes, multiple sclerosis, ulcerative colitis, rheumatoid arthritis, schizophrenia and epilepsy. The main one studied is known as ‘cannabidiol’, or simply ‘CBD’ for short. But why is CBD so special? Well, it’s NOT psycho-active. It doesn’t produce the euphoric effects that THC is famous for because it simply doesn’t bind to, and activate, CB1 receptors. It’s also the second most prevalent cannabinoid found in the cannabis plant, which makes growing and extracting it relatively easy.

“If CBD doesn’t bind to CB1 receptors then how does it work?” The thing is we just don’t know. There are many other receptors that have been reported to be implicated in the mechanism of action of CBD, such as the ‘capsaicin receptor’ (TRPV1), the most common serotonin receptor subtype (5-HT1A) and the ‘orphan cannabinoid receptor’ (GPR55). However, none of the effects of CBD at these receptors are convincing enough for the world’s leading cannabinoid scientists to stand up and say “CBD is a potent agonist/antagonist at this receptor and that is how CBD mediates all of its pharmacological effects”.

“What has all this got to do with your PhD?” Over the last couple of years there’s been a surge in interest, particularly the USA, in people with epilepsy using whole cannabis extracts to reduce the frequency of their seizures. This isn’t anything particularly new as cannabis has been used as a medicine for thousands of years. However, the thing that has made people sit up and notice is the fact that some children with severe epilepsy, in which their seizures cannot be controlled and is therefore life-threatening, have been given extracts of cannabis, in which CBD is the main component, and their seizures have dramatically reduced in both severity and frequency. You can read a couple of articles from CNN here: Jayden David and Charlotte Figi.

Unfortunately there are some issues with using homegrown cannabis preparations such as medical marijuana.

Firstly, the preparations still contain a significant amount of THC, despite growers’ best efforts to produce plants that predominantly contain CBD. Also, we still have no idea what the impact of regular THC exposure has on an adult’s brain, let alone a child’s brain and their neurological development.

Secondly, the preparations are unregulated and inconsistent. The relative proportions of cannabinoids present will vary depending on the growing conditions, the methods of extraction and the preparation of the final product. This is a major problem for people with epilepsy. I spoke to someone from California, who sometimes takes medical marijuana for their epilepsy, and he told me that whenever he went to the dispensary to get medical marijuana he had no idea what he was getting in terms of THC levels. He wants to be able to lead a normal life and have a job, but he can’t do that when he’s high on medical marijuana with too much THC in it. Also, in terms of being able to control seizures, it’s extremely important for medication to be consistent. Even a slight change in regime, dose or drug can potentially result in rebound seizures and do more harm than good.

Finally, there are legal restrictions on the use of cannabis-derived medicine in research. Currently in the USA, CBD is classified as a Schedule 1 controlled substance and federal law prohibits its use, even for research, despite the fact that it is NOT psycho-active. Yet, paradoxically, medical marijuana containing THC is available for ‘medical’ uses in about a third of the states in the USA. When I attended a conference in San Diego, California last year, I was astounded by the sheer number of American researchers telling me how incredibly lucky I was to be able to do research on plant-derived cannabinoids (particularly CBD).

I personally think that we need to move away from medical marijuana and pay more attention to regulated botanical drug substances (BDSs) derived from cannabis, in addition to isolated and purified non-psycho-active phytocannabinoids. Thankfully this has already been going on for many years by the pharmaceutical company who sponsor my PhD (GW Pharmaceuticals).

Presenting my research at Neuroscience 2013. Photo courtesy of Immy Smith

Presenting my research at Neuroscience 2013. Photo courtesy of Immy Smith

“OK, but I still don’t get what your PhD is all about…” Right, so I’ve already explained that (anecdotally) cannabis and components of the cannabis plant (eg. CBD) can treat people with epilepsy. For over a decade now, scientists have been conducting pre-clinical studies in order to put together enough evidence that justifies putting non-psychoactive plant-derived cannabinoids through clinical trials for epilepsy. This basically means that several PhD students, like myself, have been doing experiments on live animals or tissue taken from dead animals, in order to justify giving these drugs to people who have a life-threatening disease. I must also point out here that the animals used in these experiments are rats and mice, and that every person doing experiments with live animals MUST hold a personal Home Office license – I will go into more detail about this another time.

Preparations for electrophysiological experiments. Photos courtesy of Tom Hill

Preparations for my electrophysiological experiments on fresh rat brain. Photos courtesy of Tom Hill

So, clinical trials are currently underway at GW, which means that we know at least 2 non-psycho-active phytocannabinoids (CBD and its propyl analogue CBDV) definitely work in animal models of seizure and epilepsy.

But the burning question is “How do these compounds work as anti-convulsant and anti-epileptic drugs?” Well, that’s where my PhD project steps in. I’ve been doing electrophysiological experiments for the last 3 years in an attempt to figure out how these compounds, CBDV in particular, work as anti-convulsant and anti-epileptic drugs. I do this by taking recordings from individual brain cells, as well as networks of brain cells, from fresh rat brain slices. I record what brain cells do under ‘normal’ conditions and then record them again under ‘drug’ conditions and see if there’s a difference. I also record the ‘normal’ and ‘drugged’ activity of brain cells from rats that were epileptic. To then add another level of complexity, I compare the differences between non-epileptic brain cells and epileptic brain cells in terms of their response to the drug.

“Yikes! Now my brain hurts” If you want something that’s a little easier to understand (and A LOT more fun) then you can watch my Science Slam.

“So what have you discovered?” That there are no easy answers in science. Every time I think I’m getting close to answering a particular question, more questions spring up in its place. I suppose in that regard, conducting scientific research is a bit like fighting the Lernaean Hydra. I’ve also discovered that electrophysiology is a cruel and fickle mistress.

In terms of actually discovering something that makes a substantial contribution to science, I’m afraid I can’t say at this point. This is not necessarily because I haven’t found something, it’s more about keeping everything under wraps until I am permitted to reveal all. But don’t worry, there are a few papers in the pipeline.

You can read more about the case for medical marijuana in epilepsy, the case for assessing cannabidiol in epilepsy and a critical review about CBD and its therapeutic role in epilepsy and other neurological disorders for free in the journal Epilepsia.

 

05/08/2014 edit: It’s been brought to my attention that the Epilepsia articles are no longer free to view. If you really want to read them, but can’t get access – let me know and I’ll see what I can do 🙂

For the love of brain (well, the hippocampus) II

So I’ve already described how much I love being able to look at live, functional neurons in real time. But there are other things I enjoy seeing everyday too, in particular my favourite part of the brain; the hippocampus.

The rodent hippocampus in stained, coronal sections

The rodent hippocampus in stained, sequential coronal sections

At the start of every patch clamp experiment, when I look down the microscope at a brain slice, I need to locate a specific structure before I can focus on finding individual neurons. This structure is called the hippocampus (so called because a cross section of it looks like a seahorse) and every brain has a pair of them (one in each hemisphere). The hippocampus is very special because it has a well-defined and distinctive structure, which makes it instantly recognisable to anyone who has studied neuroanatomy.

Freshly cut transverse brain slices. I store them in a plastic tea strainer, submerged in  carboxygentated aCSF. The arrow points to where the hippocampus is loacted

Freshly cut transverse brain slices. I store them in a plastic tea strainer, submerged in carboxygentated aCSF. The arrow points to where the hippocampus is located

 

Acute, transverse hippocampus as seen during my patch experiments - notice the patch electrode emerging from the CA1 region in the right-side image

Acute, transverse hippocampus as seen during my patch experiments – notice the patch electrode emerging from the top of the CA1 region in the image on the right

As I’ve said before, the brain is not a homogenous blob, but contains many intricate and beautiful structures. Many of these structures look pretty much the same across the majority of species, no matter what size or shape the brain may be, and the hippocampus is no exception.

Drawing by Camillo Golgi of a hippocampus stained using silver nitrate

Drawing by Camillo Golgi of a hippocampus stained using silver nitrate

Why do I love the hippocampus? Well, for one thing I love how ‘organised’ the anatomy is (I won’t go into detail here, but I do find the Wikipedia page extremely useful). The hippocampus is a network and I love how you can stimulate a particular pathway and get other neurons to fire in response (ie. stimulate the axons of the CA3 pyramidal neurons and the CA1 pyramidal neurons will produce a response). I also love the fact that it’s involved in lots of different aspects of learning and memory.

So, going back to the point about being able to stimulate pathways in the hippocampus, I also do a lot of experiments using multi-electrode arrays (MEAs). Being able to stimulate particular pathways and measuring evoked responses can tell you a lot about the synapse involved and the neurons on either side. For my experiments, I stimulate the Schaffer collaterals (axons of CA3 pyramidal neurons) and record the responses of the CA1 pyramidal neurons. Instead of observing signals from individual neurons, I look at the combined response of a whole population of neurons, which all fire in unison when stimulated by an extracellular electrode.

I take a photograph (before and after!) of every hippocampus I use for my MEA experiments. It allows me to select which electrodes to stimulate so that I can record evoked field potentials

I take a photograph of every hippocampus I use for my MEA experiments so that I can select which electrodes to stimulate in order to produce evoked responses. This is not a stained section – it’s the actual colour of a ‘living’ hippocampus!

I’d love to go into more detail about MEA experiments, but I’ll save it for another post 🙂