Undergraduate Course

Department of Chemistry University of Oxford
Research Topic and Supervisor willing to supervise Chemistry Part II students.

MChem Pt II Project Description

Title: Electrochemical analysis of synaptic dopamine release in the brain

Supervisor: Professor S.J. Cragg
University Lecturer, Dept. Physiology, Anatomy & Genetics; Tutor, Christ Church
E-mail: stephanie.cragg@dpag.ox.ac.uk.
Tel: 282513
Department: Physiology, Anatomy & Genetics, Sherrington Building

Outline
Neuron-to-neuron communication in the brain occurs by the release and detection of chemical neurotransmitters. The catecholamine neurotransmitter dopamine in the brain region called the striatum is critical to how we select our actions, and to disorders such as Parkinson’s disease and addictions. However, our knowledge of the mechanisms that govern dopamine function is far from complete. New data suggest that mechanisms on axons have powerful roles in determining dopamine transmission (e.g. Threlfell et al 2012), and we need to understand such mechanisms if we are to understand dopamine function fully.

Electrochemical analytical techniques such as voltammetry, can be used in the brain to monitor neurotransmitters, notably the monoamines dopamine, noradrenaline and serotonin (Troyer et al., 2002; Phillips and Wightman, 2003). By using a microelectrode, voltammetry can detect neurotransmitter release on a timescale that parallels physiological functions (Robinson et al., 2008; Rice and Cragg, 2004). This project will use fast-scan cyclic voltammetry at carbon-fibre microelectrodes in conjunction with new technologies such as optogenetics, to monitor and explore the neurochemical mechanisms that govern the release of dopamine (e.g. Rice and Cragg 2004; Threlfell and Cragg 2006). In overview, the project will involve exploring the control of dopamine release by specific neurochemical receptors or drugs. These studies will be done in regions of the brain in which dysfunction is associated with drug addiction and Parkinson’s disease. Thus, this project should not only shed light on fundamental mechanisms of neurochemical signalling by the brain, but may also offer insights into disease.

Background references

  1. Phillips PEM, Wightman RM (2003) Critical guidelines for validation of the selectivity of in vivo chemical microsensors. Trends Anal Chem 22:509-514.
  2. Rice ME, Cragg SJ (2004) Nicotine amplifies reward-related dopamine signals in striatum. Nat Neurosci 7:583-584.
  3. Robinson DL, Hermans A, Seipel AT, Wightman RM (2008) Monitoring Rapid Chemical Communication in the Brain. Chemical Reviews 108:2554-2584.
  4. Threlfell S, Lalic T, Platt NJ, Jennings KA, Deisseroth K, Cragg SJ (2012) Striatal Dopamine Release Is Triggered by Synchronized Activity in Cholinergic Interneurons. Neuron 75:58-64.
  5. Troyer KP, Heien ML, Venton BJ, Wightman RM (2002) Neurochemistry and electroanalytical probes. Curr Opin Chem Biol 6:696-703.


Supervisor: Professor Kieran Clarke
Maximum number of students: 3
Telephone number: 282248
Email: kieran.clarke@dpag.ox.ac.uk
Webpage: http://www.dpag.ox.ac.uk/academic_staff/kieran_clarke/

Supervisors:   Professor Kieran Clarke, DPAG
                      Prof. Jeremy Robertson, Department of Chemistry

‘Ketone bodies’ (acetone, acetoacetate, and b-hydroxybutyrate) are produced by the liver from fatty acids, which are released from adipose tissue in times of starvation to be used as an energy source.1 Ketones constitute an efficient form of food that is absorbed very rapidly by most organs including the brain which, in fact, can make direct use of only two nutritional substances: glucose and ketone bodies. Ketone bodies provide an effective means of increasing metabolic efficiency, and high fat ketogenic diets, which increase ketone body levels in the bloodstream, are already used to treat a number of clinical conditions, such as epilepsy and Parkinson’s disease, 2,3

Although ketone bodies are produced naturally by the body, they are not found in meaningful quantities in any existing food. The Robertson and Clarke groups have identified a specific ketone body precursor, a stable, benign ester that is broken down in the body to produce b-hydroxybutyrate: (R)-3-hydroxybutyl (R)-3-hydroxybutyrate.4,5  This ester has been used as a food in humans to elevate the levels of ketone bodies available to the brain and skeletal muscle to enhance physical performance in athletes and patients with type 2 diabetes. (R)-3-Hydroxybutyl (R)-3-hydroxybutyrate has the potential to provide nutritional effects in a wide range of applications. See http://www.tdeltas.com for further details.

This project will develop chemical syntheses of new candidate ketone body precursors and evaluate the candidates for their suitability as the active constituent in ketogenic diets. Requirements for the candidates include: non-toxicity, palatability, and the ability to effectively raise ketone body levels circulating in the blood over several hours. Candidates based on precursors to, and derivatives of, acetoacetic acid, R-3-hydroxybutyrate and R-butane-1,3-diol will require minimal metabolic conversion to active ketone bodies. Therefore, by linking combinations of these molecular components (in precursor or derivative form) within one molecule, ketone bodies should be released into the blood stream following processing by gut esterases. A key requirement will be to ensure that ancillary molecular components are also non-toxic, are preferably metabolized to provide energy, and do not cause undesirable effects.

The synthetic chemistry will be developed and carried out in Dr Robertson’s laboratory and candidates will be evaluated in Professor Clarke’s laboratory, firstly in blood and then in rats to determine the levels of circulating ketones.  For candidates that prove to be more effective than the current ketone body precursor, methods will be developed for their synthesis on sufficient scales to enable more detailed testing in rats.

1.    Clarke K, Tchabanenko K, Pawlosky R, Carter E, Knight NS, Murray AJ, Cochlin LE, King MT, Wong AW, Roberts A, Robertson J, Veech RL. Oral 28-day and developmental toxicity studies of (r)-3-hydroxybutyl (r)-3-hydroxybutyrate. Regul Toxicol Pharmacol. 2012; 63: 196-208.

2.    Clarke K, Tchabanenko K, Pawlosky R, Carter E, Todd King M, Musa-Veloso K, Ho M, Roberts A, Robertson J, VanItallie TB, Veech RL. Kinetics, safety and tolerability of (r)-3-hydroxybutyl (r)-3-hydroxybutyrate in healthy adult subjects. Regul Toxicol Pharmacol. 2012; 63: 401-408.

3.    Cox PJ and Clarke K. Acute nutritional ketosis: implications for exercise performance and metabolism. Extreme Physiol Med 2014; 3: 17-26.

4.    Cox PJ, Kirk T, Ashmore T, Willerton K, Evans R, Smith A, Murray AJ, Stubbs B, West J, McLure SW, King MT, Dodd MS, Holloway C, Neubauer S, Drawer S, Veech RL, Griffin JL and Clarke K.  Nutritional ketosis alters fuel preference and thereby endurance performance in athletes.  Cell Metab. 2016; 24: 256-268.

5.    Kashiwaya Y, Bergman C, Lee JH, Wan R, King MT, Mughal MR, Okun E, Clarke K, Mattson MP, Veech RL. A ketone ester diet exhibits anxiolytic and cognition-sparing properties, and lessens amyloid and tau pathologies in a mouse model of Alzheimer's disease. Neurobiol Aging. 2013; 34: 1530-1539.

6.    Kemper MF, Srivastava S, King MT, Clarke K, Veech RL and Pawlosky RJ. An ester of β-hydroxybutyrate regulates cholesterol biosynthesis in rats and a cholesterol biomarker in humans.  Lipids 2015; 50: 1185-1193.

7.    Murray AJ, Knight NS, Cole MA, Cochlin LE, Carter E, Tchabanenko K, Pichulik T, Gulston MK, Atherton HJ, Schroeder MA, Deacon RAMJ, Kashiwaya Y, King MT, Pawlosky R, Rawlins JNP, Tyler DJ, Griffin JL, Robertson J, Veech RL, Clarke K.  Novel ketone diet enhances physical and cognitive performance.  FASEB J 2016; 30: 2689-97.