Rafat Adbdulhassan Mohammed Jawad

2016 AFPGR Participant

 

Sucrose addiction: Learn how sugar can affect your behaviour by using flatworms as a model
About Rafat

I am a research student working towards completion of my doctoral degree in Pharmacology in the Department of Neuroscience, Psychology and Behaviour, Collage of Medicine, Biological science and Psychology. I am supervised by Dr. Jose Prados and Dr. Claire V. Hutchinson.

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About My Research

The main focus of my PhD project is to use the invertebrate flatworm, planaria, as a model for addiction research. Planaria have a nervous system with key similarities to that of vertebrates. Importantly, they possess the same main neurotransmitters as those found in vertebrates, especially those involved in behaviour and learning mechanisms. These include Serotonin, Acetylcholine, Gama amino butyric acid, glutamate, aspartate and catecholamines such as dopamine and norepinephrine. From a behavioural perspective, there is also robust evidence that planaria can learn, remember and display a clear response to drugs commonly-abused by humans. As such, they represent a potentially useful model for studying drugs addiction, learning mechanisms and behaviour.

An invertebrate model of addiction would provide an excellent opportunity for understanding the mechanisms that lead to the development of substance abuse and addiction. In the longer term this pre-clinical research would provide a basis to develop therapeutic strategies to address the problem in vertebrate animal models and in humans.

The experiments described below use sucrose to study addictive behaviour in planaria. Sucrose is an example of a natural substance that can cause addiction-like behaviour. In studies using rats, it has been shown that sucrose results in signs of drug addiction, such as physical dependence, dopamine release in the brain and withdrawal-like symptoms. The abuse of sucrose and the development of sucrose addiction could play a relevant role in eating disorders like obesity and binge eating, which are also important public health problems.

About My Research Approach

During the first year of my PhD study, I have concentrated on three main signs of addiction: withdrawal, tolerance and place preference. The experiments I have done so far address the effects of sucrose in the planaria as well as the development of addictive-like behaviour to sucrose in this invertebrate model. Two methods were used: withdrawal and conditioned place preference (CPP). In the withdrawal experiments, the effect of single and repeated exposure to sucrose were studied. Animals were exposed to sucrose in one context, and then tested in the same or in a different context. Our hypothesis was that the establishment of associations between the contextual cues and the post-effects of sucrose (a compensatory response which counteracts the effects of sucrose) would lead to the expression of the compensatory response in the training context. In the CPP experiments, it was expected that animals exposed to a context in the presence of sucrose would develop a preference for this context. Our experiments show that this learning is dependent on the dopaminergic system: animals treated with a dopamine antagonist do not develop CPP. Also, learning of the context preference seems to depend upon the same principles of Pavlovian conditioning in vertebrates: exposure to the context in the absence of the sucrose results in extinction of the conditioned preference, although one single exposure to the sucrose in a different context reinstates the learned preference.

Research Findings and Future Work

From my research, I have found acquisition and extinction of a conditioned response, as well as its reinstatement following exposure to the reward. These findings suggest that learning in planaria is governed by the same principles that govern learning in vertebrate animals. The fact that planaria display CPP, tolerance and withdrawal behaviour to sucrose and this CPP is dependent upon the dopamine reward system, makes them a useful model for the research of addictive behaviours.

The next step in my PhD project will be to complete the experiments using the behaviour protocols outlined above, examining whether treating the animals with dopamine antagonist drug alone results in aversive conditioning in animals. I also will study the ability of the aversive stimuli in changing the behaviour by performing between and within-subjects designs using other hallmarks of learning; and studying the role of dopamine agonist and antagonist in latent inhibition. The second part of my project is a pharmacological protocol: I will study the mechanism of abused drugs such as amphetamine in planaria and explore whether they have a similar effects as in vertebrates.

Presenters_Hannah and Rafat
Rafat Standing (foreground) by her poster at the 2016 Festival of Postgraduate Research

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