David Sugden

Melatonin: The pineal hormone, melatonin shows a dramatic, precisely-regulated circadian rhythm of synthesis and release. It acts through specific, high affinity, G-protein-coupled cell membrane receptors to regulate circadian and seasonal physiological changes. We are involved in a collaborations with chemists at University College London and the University of Athens to design, synthesize and evaluate novel melatonin analogs. The project aims to understand the molecular basis of the recognition of melatonin, receptor activation and subtype specificity. We have developed some of the first subtype selective melatonin receptor agonists and antagonists. Novel analogues are examined in vitro, and in cell systems. In addition, in vivo effects on circadian rhythms in activity, temperature and sleep are monitored by telemetry. We are currently investigating the role of endogenous melatonin in sleep, and the mechanism of action of exogenous melatonin as a hypnotic. Melatonin analogs have recently been licensed for sleep problems and depression. Chronic sleep disturbance (often caused by desynchronised circadian rhythms) is increasingly recognised as an important risk factor for cardiovascular disease and metabolic disorders. We are interested in the effects of circadian disruption on health and have substantial experience of using radiotelemetry in small animals for chronic measurement of physiology and behaviour.<br /> Quantitation of gene expression: Over several years the group has built expertise and state-of-the-art facilities for gene expression analysis using qPCR and has played a major role in spreading best practice in this technique in the UK through a variety of training courses attracting participants from the UK, Europe, South America and the Middle East. I am involved with a number of projects using real-time RT-PCR to quantitate steady-state levels of gene expression in various endocrine and neural cells and tissues. One of these projects in collaboration with Dr David Klein (NIH, USA) is a detailed examination of the circadian control of the expression of the genes encoding proteins (receptors, enzymes, transcription factors etc.) known to be important for the nocturnal synthesis of melatonin. Others include studies using qPCR assays to validate microarray data.. <br /> Melanopsin: Melanopsin is a novel, retinal, opsin-like protein, first identified in skin cells (melanophores) of Xenopus leavis. Recent work shows that it acts as light detector mediating the entraining action of light on the circadian clock in the SCN, and various other effects of light. We are using a Xenopus melanophore cell line, which naturally expresses melanopsin and also responds to light with a dramatic redistribution of pigment granules, as a model system to study melanopsin photo-biology, signal transduction mechanisms and function.<br /> <br />

melatonin actions and receptor pharmacology; regulation of melatonin synthesis; quantitative real-time PCR.