"Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:rhodes/vital:4391 |
| Date | January 2003 |
| Creators | Lack, Barbara Anne |
| Publisher | Rhodes University, Faculty of Science, Chemistry |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Doctoral, PhD |
| Format | 226 leaves, pdf |
| Rights | Lack, Barbara Anne |
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